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![Johannes Weiner](/assets/img/avatar_default.png)
Commit 3812c8c8f3
("mm: memcg: do not trap chargers with full
callstack on OOM") assumed that only a few places that can trigger a
memcg OOM situation do not return VM_FAULT_OOM, like optional page cache
readahead. But there are many more and it's impractical to annotate
them all.
First of all, we don't want to invoke the OOM killer when the failed
allocation is gracefully handled, so defer the actual kill to the end of
the fault handling as well. This simplifies the code quite a bit for
added bonus.
Second, since a failed allocation might not be the abrupt end of the
fault, the memcg OOM handler needs to be re-entrant until the fault
finishes for subsequent allocation attempts. If an allocation is
attempted after the task already OOMed, allow it to bypass the limit so
that it can quickly finish the fault and invoke the OOM killer.
Reported-by: azurIt <azurit@pobox.sk>
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2596 lines
68 KiB
C
2596 lines
68 KiB
C
/*
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* linux/mm/filemap.c
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*
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* Copyright (C) 1994-1999 Linus Torvalds
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*/
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/*
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* This file handles the generic file mmap semantics used by
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* most "normal" filesystems (but you don't /have/ to use this:
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* the NFS filesystem used to do this differently, for example)
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*/
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#include <linux/export.h>
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#include <linux/compiler.h>
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#include <linux/fs.h>
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#include <linux/uaccess.h>
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#include <linux/aio.h>
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#include <linux/capability.h>
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#include <linux/kernel_stat.h>
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#include <linux/gfp.h>
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#include <linux/mm.h>
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#include <linux/swap.h>
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#include <linux/mman.h>
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#include <linux/pagemap.h>
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#include <linux/file.h>
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#include <linux/uio.h>
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#include <linux/hash.h>
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#include <linux/writeback.h>
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#include <linux/backing-dev.h>
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#include <linux/pagevec.h>
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#include <linux/blkdev.h>
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#include <linux/security.h>
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#include <linux/cpuset.h>
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#include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */
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#include <linux/memcontrol.h>
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#include <linux/cleancache.h>
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#include "internal.h"
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#define CREATE_TRACE_POINTS
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#include <trace/events/filemap.h>
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/*
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* FIXME: remove all knowledge of the buffer layer from the core VM
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*/
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#include <linux/buffer_head.h> /* for try_to_free_buffers */
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#include <asm/mman.h>
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/*
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* Shared mappings implemented 30.11.1994. It's not fully working yet,
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* though.
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*
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* Shared mappings now work. 15.8.1995 Bruno.
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*
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* finished 'unifying' the page and buffer cache and SMP-threaded the
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* page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
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*
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* SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
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*/
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/*
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* Lock ordering:
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*
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* ->i_mmap_mutex (truncate_pagecache)
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* ->private_lock (__free_pte->__set_page_dirty_buffers)
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* ->swap_lock (exclusive_swap_page, others)
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* ->mapping->tree_lock
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*
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* ->i_mutex
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* ->i_mmap_mutex (truncate->unmap_mapping_range)
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*
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* ->mmap_sem
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* ->i_mmap_mutex
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* ->page_table_lock or pte_lock (various, mainly in memory.c)
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* ->mapping->tree_lock (arch-dependent flush_dcache_mmap_lock)
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*
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* ->mmap_sem
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* ->lock_page (access_process_vm)
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*
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* ->i_mutex (generic_file_buffered_write)
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* ->mmap_sem (fault_in_pages_readable->do_page_fault)
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*
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* bdi->wb.list_lock
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* sb_lock (fs/fs-writeback.c)
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* ->mapping->tree_lock (__sync_single_inode)
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*
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* ->i_mmap_mutex
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* ->anon_vma.lock (vma_adjust)
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*
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* ->anon_vma.lock
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* ->page_table_lock or pte_lock (anon_vma_prepare and various)
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*
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* ->page_table_lock or pte_lock
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* ->swap_lock (try_to_unmap_one)
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* ->private_lock (try_to_unmap_one)
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* ->tree_lock (try_to_unmap_one)
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* ->zone.lru_lock (follow_page->mark_page_accessed)
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* ->zone.lru_lock (check_pte_range->isolate_lru_page)
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* ->private_lock (page_remove_rmap->set_page_dirty)
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* ->tree_lock (page_remove_rmap->set_page_dirty)
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* bdi.wb->list_lock (page_remove_rmap->set_page_dirty)
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* ->inode->i_lock (page_remove_rmap->set_page_dirty)
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* bdi.wb->list_lock (zap_pte_range->set_page_dirty)
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* ->inode->i_lock (zap_pte_range->set_page_dirty)
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* ->private_lock (zap_pte_range->__set_page_dirty_buffers)
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*
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* ->i_mmap_mutex
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* ->tasklist_lock (memory_failure, collect_procs_ao)
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*/
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/*
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* Delete a page from the page cache and free it. Caller has to make
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* sure the page is locked and that nobody else uses it - or that usage
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* is safe. The caller must hold the mapping's tree_lock.
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*/
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void __delete_from_page_cache(struct page *page)
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{
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struct address_space *mapping = page->mapping;
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trace_mm_filemap_delete_from_page_cache(page);
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/*
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* if we're uptodate, flush out into the cleancache, otherwise
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* invalidate any existing cleancache entries. We can't leave
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* stale data around in the cleancache once our page is gone
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*/
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if (PageUptodate(page) && PageMappedToDisk(page))
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cleancache_put_page(page);
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else
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cleancache_invalidate_page(mapping, page);
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radix_tree_delete(&mapping->page_tree, page->index);
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page->mapping = NULL;
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/* Leave page->index set: truncation lookup relies upon it */
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mapping->nrpages--;
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__dec_zone_page_state(page, NR_FILE_PAGES);
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if (PageSwapBacked(page))
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__dec_zone_page_state(page, NR_SHMEM);
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BUG_ON(page_mapped(page));
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/*
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* Some filesystems seem to re-dirty the page even after
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* the VM has canceled the dirty bit (eg ext3 journaling).
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*
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* Fix it up by doing a final dirty accounting check after
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* having removed the page entirely.
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*/
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if (PageDirty(page) && mapping_cap_account_dirty(mapping)) {
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dec_zone_page_state(page, NR_FILE_DIRTY);
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dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
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}
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}
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/**
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* delete_from_page_cache - delete page from page cache
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* @page: the page which the kernel is trying to remove from page cache
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*
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* This must be called only on pages that have been verified to be in the page
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* cache and locked. It will never put the page into the free list, the caller
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* has a reference on the page.
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*/
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void delete_from_page_cache(struct page *page)
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{
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struct address_space *mapping = page->mapping;
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void (*freepage)(struct page *);
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BUG_ON(!PageLocked(page));
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freepage = mapping->a_ops->freepage;
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spin_lock_irq(&mapping->tree_lock);
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__delete_from_page_cache(page);
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spin_unlock_irq(&mapping->tree_lock);
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mem_cgroup_uncharge_cache_page(page);
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if (freepage)
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freepage(page);
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page_cache_release(page);
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}
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EXPORT_SYMBOL(delete_from_page_cache);
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static int sleep_on_page(void *word)
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{
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io_schedule();
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return 0;
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}
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static int sleep_on_page_killable(void *word)
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{
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sleep_on_page(word);
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return fatal_signal_pending(current) ? -EINTR : 0;
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}
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static int filemap_check_errors(struct address_space *mapping)
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{
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int ret = 0;
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/* Check for outstanding write errors */
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if (test_and_clear_bit(AS_ENOSPC, &mapping->flags))
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ret = -ENOSPC;
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if (test_and_clear_bit(AS_EIO, &mapping->flags))
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ret = -EIO;
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return ret;
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}
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/**
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* __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
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* @mapping: address space structure to write
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* @start: offset in bytes where the range starts
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* @end: offset in bytes where the range ends (inclusive)
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* @sync_mode: enable synchronous operation
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*
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* Start writeback against all of a mapping's dirty pages that lie
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* within the byte offsets <start, end> inclusive.
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*
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* If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
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* opposed to a regular memory cleansing writeback. The difference between
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* these two operations is that if a dirty page/buffer is encountered, it must
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* be waited upon, and not just skipped over.
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*/
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int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
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loff_t end, int sync_mode)
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{
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int ret;
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struct writeback_control wbc = {
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.sync_mode = sync_mode,
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.nr_to_write = LONG_MAX,
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.range_start = start,
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.range_end = end,
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};
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if (!mapping_cap_writeback_dirty(mapping))
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return 0;
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ret = do_writepages(mapping, &wbc);
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return ret;
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}
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static inline int __filemap_fdatawrite(struct address_space *mapping,
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int sync_mode)
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{
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return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
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}
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int filemap_fdatawrite(struct address_space *mapping)
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{
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return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
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}
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EXPORT_SYMBOL(filemap_fdatawrite);
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int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
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loff_t end)
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{
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return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
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}
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EXPORT_SYMBOL(filemap_fdatawrite_range);
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/**
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* filemap_flush - mostly a non-blocking flush
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* @mapping: target address_space
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*
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* This is a mostly non-blocking flush. Not suitable for data-integrity
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* purposes - I/O may not be started against all dirty pages.
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*/
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int filemap_flush(struct address_space *mapping)
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{
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return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
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}
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EXPORT_SYMBOL(filemap_flush);
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/**
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* filemap_fdatawait_range - wait for writeback to complete
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* @mapping: address space structure to wait for
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* @start_byte: offset in bytes where the range starts
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* @end_byte: offset in bytes where the range ends (inclusive)
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*
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* Walk the list of under-writeback pages of the given address space
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* in the given range and wait for all of them.
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*/
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int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
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loff_t end_byte)
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{
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pgoff_t index = start_byte >> PAGE_CACHE_SHIFT;
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pgoff_t end = end_byte >> PAGE_CACHE_SHIFT;
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struct pagevec pvec;
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int nr_pages;
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int ret2, ret = 0;
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if (end_byte < start_byte)
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goto out;
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pagevec_init(&pvec, 0);
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while ((index <= end) &&
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(nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
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PAGECACHE_TAG_WRITEBACK,
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min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) {
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unsigned i;
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for (i = 0; i < nr_pages; i++) {
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struct page *page = pvec.pages[i];
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/* until radix tree lookup accepts end_index */
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if (page->index > end)
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continue;
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wait_on_page_writeback(page);
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if (TestClearPageError(page))
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ret = -EIO;
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}
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pagevec_release(&pvec);
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cond_resched();
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}
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out:
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ret2 = filemap_check_errors(mapping);
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if (!ret)
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ret = ret2;
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return ret;
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}
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EXPORT_SYMBOL(filemap_fdatawait_range);
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/**
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* filemap_fdatawait - wait for all under-writeback pages to complete
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* @mapping: address space structure to wait for
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*
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* Walk the list of under-writeback pages of the given address space
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* and wait for all of them.
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*/
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int filemap_fdatawait(struct address_space *mapping)
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{
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loff_t i_size = i_size_read(mapping->host);
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if (i_size == 0)
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return 0;
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return filemap_fdatawait_range(mapping, 0, i_size - 1);
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}
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EXPORT_SYMBOL(filemap_fdatawait);
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int filemap_write_and_wait(struct address_space *mapping)
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{
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int err = 0;
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if (mapping->nrpages) {
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err = filemap_fdatawrite(mapping);
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/*
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* Even if the above returned error, the pages may be
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* written partially (e.g. -ENOSPC), so we wait for it.
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* But the -EIO is special case, it may indicate the worst
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* thing (e.g. bug) happened, so we avoid waiting for it.
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*/
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if (err != -EIO) {
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int err2 = filemap_fdatawait(mapping);
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if (!err)
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err = err2;
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}
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} else {
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err = filemap_check_errors(mapping);
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}
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return err;
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}
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EXPORT_SYMBOL(filemap_write_and_wait);
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/**
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* filemap_write_and_wait_range - write out & wait on a file range
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* @mapping: the address_space for the pages
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* @lstart: offset in bytes where the range starts
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* @lend: offset in bytes where the range ends (inclusive)
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*
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* Write out and wait upon file offsets lstart->lend, inclusive.
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*
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* Note that `lend' is inclusive (describes the last byte to be written) so
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* that this function can be used to write to the very end-of-file (end = -1).
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*/
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int filemap_write_and_wait_range(struct address_space *mapping,
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loff_t lstart, loff_t lend)
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{
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int err = 0;
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if (mapping->nrpages) {
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err = __filemap_fdatawrite_range(mapping, lstart, lend,
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WB_SYNC_ALL);
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/* See comment of filemap_write_and_wait() */
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if (err != -EIO) {
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int err2 = filemap_fdatawait_range(mapping,
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lstart, lend);
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if (!err)
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err = err2;
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}
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} else {
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err = filemap_check_errors(mapping);
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}
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return err;
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}
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EXPORT_SYMBOL(filemap_write_and_wait_range);
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|
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/**
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* replace_page_cache_page - replace a pagecache page with a new one
|
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* @old: page to be replaced
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* @new: page to replace with
|
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* @gfp_mask: allocation mode
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*
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* This function replaces a page in the pagecache with a new one. On
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* success it acquires the pagecache reference for the new page and
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* drops it for the old page. Both the old and new pages must be
|
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* locked. This function does not add the new page to the LRU, the
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* caller must do that.
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*
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* The remove + add is atomic. The only way this function can fail is
|
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* memory allocation failure.
|
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*/
|
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int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
|
|
{
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int error;
|
|
|
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VM_BUG_ON(!PageLocked(old));
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VM_BUG_ON(!PageLocked(new));
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VM_BUG_ON(new->mapping);
|
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|
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error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
|
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if (!error) {
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struct address_space *mapping = old->mapping;
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void (*freepage)(struct page *);
|
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|
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pgoff_t offset = old->index;
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freepage = mapping->a_ops->freepage;
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page_cache_get(new);
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new->mapping = mapping;
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new->index = offset;
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|
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spin_lock_irq(&mapping->tree_lock);
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__delete_from_page_cache(old);
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error = radix_tree_insert(&mapping->page_tree, offset, new);
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BUG_ON(error);
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mapping->nrpages++;
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__inc_zone_page_state(new, NR_FILE_PAGES);
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if (PageSwapBacked(new))
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__inc_zone_page_state(new, NR_SHMEM);
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spin_unlock_irq(&mapping->tree_lock);
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/* mem_cgroup codes must not be called under tree_lock */
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mem_cgroup_replace_page_cache(old, new);
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radix_tree_preload_end();
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if (freepage)
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freepage(old);
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page_cache_release(old);
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}
|
|
|
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return error;
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}
|
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EXPORT_SYMBOL_GPL(replace_page_cache_page);
|
|
|
|
/**
|
|
* add_to_page_cache_locked - add a locked page to the pagecache
|
|
* @page: page to add
|
|
* @mapping: the page's address_space
|
|
* @offset: page index
|
|
* @gfp_mask: page allocation mode
|
|
*
|
|
* This function is used to add a page to the pagecache. It must be locked.
|
|
* This function does not add the page to the LRU. The caller must do that.
|
|
*/
|
|
int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
|
|
pgoff_t offset, gfp_t gfp_mask)
|
|
{
|
|
int error;
|
|
|
|
VM_BUG_ON(!PageLocked(page));
|
|
VM_BUG_ON(PageSwapBacked(page));
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|
|
error = mem_cgroup_cache_charge(page, current->mm,
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gfp_mask & GFP_RECLAIM_MASK);
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|
if (error)
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return error;
|
|
|
|
error = radix_tree_maybe_preload(gfp_mask & ~__GFP_HIGHMEM);
|
|
if (error) {
|
|
mem_cgroup_uncharge_cache_page(page);
|
|
return error;
|
|
}
|
|
|
|
page_cache_get(page);
|
|
page->mapping = mapping;
|
|
page->index = offset;
|
|
|
|
spin_lock_irq(&mapping->tree_lock);
|
|
error = radix_tree_insert(&mapping->page_tree, offset, page);
|
|
radix_tree_preload_end();
|
|
if (unlikely(error))
|
|
goto err_insert;
|
|
mapping->nrpages++;
|
|
__inc_zone_page_state(page, NR_FILE_PAGES);
|
|
spin_unlock_irq(&mapping->tree_lock);
|
|
trace_mm_filemap_add_to_page_cache(page);
|
|
return 0;
|
|
err_insert:
|
|
page->mapping = NULL;
|
|
/* Leave page->index set: truncation relies upon it */
|
|
spin_unlock_irq(&mapping->tree_lock);
|
|
mem_cgroup_uncharge_cache_page(page);
|
|
page_cache_release(page);
|
|
return error;
|
|
}
|
|
EXPORT_SYMBOL(add_to_page_cache_locked);
|
|
|
|
int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
|
|
pgoff_t offset, gfp_t gfp_mask)
|
|
{
|
|
int ret;
|
|
|
|
ret = add_to_page_cache(page, mapping, offset, gfp_mask);
|
|
if (ret == 0)
|
|
lru_cache_add_file(page);
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
|
|
|
|
#ifdef CONFIG_NUMA
|
|
struct page *__page_cache_alloc(gfp_t gfp)
|
|
{
|
|
int n;
|
|
struct page *page;
|
|
|
|
if (cpuset_do_page_mem_spread()) {
|
|
unsigned int cpuset_mems_cookie;
|
|
do {
|
|
cpuset_mems_cookie = get_mems_allowed();
|
|
n = cpuset_mem_spread_node();
|
|
page = alloc_pages_exact_node(n, gfp, 0);
|
|
} while (!put_mems_allowed(cpuset_mems_cookie) && !page);
|
|
|
|
return page;
|
|
}
|
|
return alloc_pages(gfp, 0);
|
|
}
|
|
EXPORT_SYMBOL(__page_cache_alloc);
|
|
#endif
|
|
|
|
/*
|
|
* In order to wait for pages to become available there must be
|
|
* waitqueues associated with pages. By using a hash table of
|
|
* waitqueues where the bucket discipline is to maintain all
|
|
* waiters on the same queue and wake all when any of the pages
|
|
* become available, and for the woken contexts to check to be
|
|
* sure the appropriate page became available, this saves space
|
|
* at a cost of "thundering herd" phenomena during rare hash
|
|
* collisions.
|
|
*/
|
|
static wait_queue_head_t *page_waitqueue(struct page *page)
|
|
{
|
|
const struct zone *zone = page_zone(page);
|
|
|
|
return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)];
|
|
}
|
|
|
|
static inline void wake_up_page(struct page *page, int bit)
|
|
{
|
|
__wake_up_bit(page_waitqueue(page), &page->flags, bit);
|
|
}
|
|
|
|
void wait_on_page_bit(struct page *page, int bit_nr)
|
|
{
|
|
DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
|
|
|
|
if (test_bit(bit_nr, &page->flags))
|
|
__wait_on_bit(page_waitqueue(page), &wait, sleep_on_page,
|
|
TASK_UNINTERRUPTIBLE);
|
|
}
|
|
EXPORT_SYMBOL(wait_on_page_bit);
|
|
|
|
int wait_on_page_bit_killable(struct page *page, int bit_nr)
|
|
{
|
|
DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
|
|
|
|
if (!test_bit(bit_nr, &page->flags))
|
|
return 0;
|
|
|
|
return __wait_on_bit(page_waitqueue(page), &wait,
|
|
sleep_on_page_killable, TASK_KILLABLE);
|
|
}
|
|
|
|
/**
|
|
* add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
|
|
* @page: Page defining the wait queue of interest
|
|
* @waiter: Waiter to add to the queue
|
|
*
|
|
* Add an arbitrary @waiter to the wait queue for the nominated @page.
|
|
*/
|
|
void add_page_wait_queue(struct page *page, wait_queue_t *waiter)
|
|
{
|
|
wait_queue_head_t *q = page_waitqueue(page);
|
|
unsigned long flags;
|
|
|
|
spin_lock_irqsave(&q->lock, flags);
|
|
__add_wait_queue(q, waiter);
|
|
spin_unlock_irqrestore(&q->lock, flags);
|
|
}
|
|
EXPORT_SYMBOL_GPL(add_page_wait_queue);
|
|
|
|
/**
|
|
* unlock_page - unlock a locked page
|
|
* @page: the page
|
|
*
|
|
* Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
|
|
* Also wakes sleepers in wait_on_page_writeback() because the wakeup
|
|
* mechananism between PageLocked pages and PageWriteback pages is shared.
|
|
* But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
|
|
*
|
|
* The mb is necessary to enforce ordering between the clear_bit and the read
|
|
* of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()).
|
|
*/
|
|
void unlock_page(struct page *page)
|
|
{
|
|
VM_BUG_ON(!PageLocked(page));
|
|
clear_bit_unlock(PG_locked, &page->flags);
|
|
smp_mb__after_clear_bit();
|
|
wake_up_page(page, PG_locked);
|
|
}
|
|
EXPORT_SYMBOL(unlock_page);
|
|
|
|
/**
|
|
* end_page_writeback - end writeback against a page
|
|
* @page: the page
|
|
*/
|
|
void end_page_writeback(struct page *page)
|
|
{
|
|
if (TestClearPageReclaim(page))
|
|
rotate_reclaimable_page(page);
|
|
|
|
if (!test_clear_page_writeback(page))
|
|
BUG();
|
|
|
|
smp_mb__after_clear_bit();
|
|
wake_up_page(page, PG_writeback);
|
|
}
|
|
EXPORT_SYMBOL(end_page_writeback);
|
|
|
|
/**
|
|
* __lock_page - get a lock on the page, assuming we need to sleep to get it
|
|
* @page: the page to lock
|
|
*/
|
|
void __lock_page(struct page *page)
|
|
{
|
|
DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
|
|
|
|
__wait_on_bit_lock(page_waitqueue(page), &wait, sleep_on_page,
|
|
TASK_UNINTERRUPTIBLE);
|
|
}
|
|
EXPORT_SYMBOL(__lock_page);
|
|
|
|
int __lock_page_killable(struct page *page)
|
|
{
|
|
DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
|
|
|
|
return __wait_on_bit_lock(page_waitqueue(page), &wait,
|
|
sleep_on_page_killable, TASK_KILLABLE);
|
|
}
|
|
EXPORT_SYMBOL_GPL(__lock_page_killable);
|
|
|
|
int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
|
|
unsigned int flags)
|
|
{
|
|
if (flags & FAULT_FLAG_ALLOW_RETRY) {
|
|
/*
|
|
* CAUTION! In this case, mmap_sem is not released
|
|
* even though return 0.
|
|
*/
|
|
if (flags & FAULT_FLAG_RETRY_NOWAIT)
|
|
return 0;
|
|
|
|
up_read(&mm->mmap_sem);
|
|
if (flags & FAULT_FLAG_KILLABLE)
|
|
wait_on_page_locked_killable(page);
|
|
else
|
|
wait_on_page_locked(page);
|
|
return 0;
|
|
} else {
|
|
if (flags & FAULT_FLAG_KILLABLE) {
|
|
int ret;
|
|
|
|
ret = __lock_page_killable(page);
|
|
if (ret) {
|
|
up_read(&mm->mmap_sem);
|
|
return 0;
|
|
}
|
|
} else
|
|
__lock_page(page);
|
|
return 1;
|
|
}
|
|
}
|
|
|
|
/**
|
|
* find_get_page - find and get a page reference
|
|
* @mapping: the address_space to search
|
|
* @offset: the page index
|
|
*
|
|
* Is there a pagecache struct page at the given (mapping, offset) tuple?
|
|
* If yes, increment its refcount and return it; if no, return NULL.
|
|
*/
|
|
struct page *find_get_page(struct address_space *mapping, pgoff_t offset)
|
|
{
|
|
void **pagep;
|
|
struct page *page;
|
|
|
|
rcu_read_lock();
|
|
repeat:
|
|
page = NULL;
|
|
pagep = radix_tree_lookup_slot(&mapping->page_tree, offset);
|
|
if (pagep) {
|
|
page = radix_tree_deref_slot(pagep);
|
|
if (unlikely(!page))
|
|
goto out;
|
|
if (radix_tree_exception(page)) {
|
|
if (radix_tree_deref_retry(page))
|
|
goto repeat;
|
|
/*
|
|
* Otherwise, shmem/tmpfs must be storing a swap entry
|
|
* here as an exceptional entry: so return it without
|
|
* attempting to raise page count.
|
|
*/
|
|
goto out;
|
|
}
|
|
if (!page_cache_get_speculative(page))
|
|
goto repeat;
|
|
|
|
/*
|
|
* Has the page moved?
|
|
* This is part of the lockless pagecache protocol. See
|
|
* include/linux/pagemap.h for details.
|
|
*/
|
|
if (unlikely(page != *pagep)) {
|
|
page_cache_release(page);
|
|
goto repeat;
|
|
}
|
|
}
|
|
out:
|
|
rcu_read_unlock();
|
|
|
|
return page;
|
|
}
|
|
EXPORT_SYMBOL(find_get_page);
|
|
|
|
/**
|
|
* find_lock_page - locate, pin and lock a pagecache page
|
|
* @mapping: the address_space to search
|
|
* @offset: the page index
|
|
*
|
|
* Locates the desired pagecache page, locks it, increments its reference
|
|
* count and returns its address.
|
|
*
|
|
* Returns zero if the page was not present. find_lock_page() may sleep.
|
|
*/
|
|
struct page *find_lock_page(struct address_space *mapping, pgoff_t offset)
|
|
{
|
|
struct page *page;
|
|
|
|
repeat:
|
|
page = find_get_page(mapping, offset);
|
|
if (page && !radix_tree_exception(page)) {
|
|
lock_page(page);
|
|
/* Has the page been truncated? */
|
|
if (unlikely(page->mapping != mapping)) {
|
|
unlock_page(page);
|
|
page_cache_release(page);
|
|
goto repeat;
|
|
}
|
|
VM_BUG_ON(page->index != offset);
|
|
}
|
|
return page;
|
|
}
|
|
EXPORT_SYMBOL(find_lock_page);
|
|
|
|
/**
|
|
* find_or_create_page - locate or add a pagecache page
|
|
* @mapping: the page's address_space
|
|
* @index: the page's index into the mapping
|
|
* @gfp_mask: page allocation mode
|
|
*
|
|
* Locates a page in the pagecache. If the page is not present, a new page
|
|
* is allocated using @gfp_mask and is added to the pagecache and to the VM's
|
|
* LRU list. The returned page is locked and has its reference count
|
|
* incremented.
|
|
*
|
|
* find_or_create_page() may sleep, even if @gfp_flags specifies an atomic
|
|
* allocation!
|
|
*
|
|
* find_or_create_page() returns the desired page's address, or zero on
|
|
* memory exhaustion.
|
|
*/
|
|
struct page *find_or_create_page(struct address_space *mapping,
|
|
pgoff_t index, gfp_t gfp_mask)
|
|
{
|
|
struct page *page;
|
|
int err;
|
|
repeat:
|
|
page = find_lock_page(mapping, index);
|
|
if (!page) {
|
|
page = __page_cache_alloc(gfp_mask);
|
|
if (!page)
|
|
return NULL;
|
|
/*
|
|
* We want a regular kernel memory (not highmem or DMA etc)
|
|
* allocation for the radix tree nodes, but we need to honour
|
|
* the context-specific requirements the caller has asked for.
|
|
* GFP_RECLAIM_MASK collects those requirements.
|
|
*/
|
|
err = add_to_page_cache_lru(page, mapping, index,
|
|
(gfp_mask & GFP_RECLAIM_MASK));
|
|
if (unlikely(err)) {
|
|
page_cache_release(page);
|
|
page = NULL;
|
|
if (err == -EEXIST)
|
|
goto repeat;
|
|
}
|
|
}
|
|
return page;
|
|
}
|
|
EXPORT_SYMBOL(find_or_create_page);
|
|
|
|
/**
|
|
* find_get_pages - gang pagecache lookup
|
|
* @mapping: The address_space to search
|
|
* @start: The starting page index
|
|
* @nr_pages: The maximum number of pages
|
|
* @pages: Where the resulting pages are placed
|
|
*
|
|
* find_get_pages() will search for and return a group of up to
|
|
* @nr_pages pages in the mapping. The pages are placed at @pages.
|
|
* find_get_pages() takes a reference against the returned pages.
|
|
*
|
|
* The search returns a group of mapping-contiguous pages with ascending
|
|
* indexes. There may be holes in the indices due to not-present pages.
|
|
*
|
|
* find_get_pages() returns the number of pages which were found.
|
|
*/
|
|
unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
|
|
unsigned int nr_pages, struct page **pages)
|
|
{
|
|
struct radix_tree_iter iter;
|
|
void **slot;
|
|
unsigned ret = 0;
|
|
|
|
if (unlikely(!nr_pages))
|
|
return 0;
|
|
|
|
rcu_read_lock();
|
|
restart:
|
|
radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
|
|
struct page *page;
|
|
repeat:
|
|
page = radix_tree_deref_slot(slot);
|
|
if (unlikely(!page))
|
|
continue;
|
|
|
|
if (radix_tree_exception(page)) {
|
|
if (radix_tree_deref_retry(page)) {
|
|
/*
|
|
* Transient condition which can only trigger
|
|
* when entry at index 0 moves out of or back
|
|
* to root: none yet gotten, safe to restart.
|
|
*/
|
|
WARN_ON(iter.index);
|
|
goto restart;
|
|
}
|
|
/*
|
|
* Otherwise, shmem/tmpfs must be storing a swap entry
|
|
* here as an exceptional entry: so skip over it -
|
|
* we only reach this from invalidate_mapping_pages().
|
|
*/
|
|
continue;
|
|
}
|
|
|
|
if (!page_cache_get_speculative(page))
|
|
goto repeat;
|
|
|
|
/* Has the page moved? */
|
|
if (unlikely(page != *slot)) {
|
|
page_cache_release(page);
|
|
goto repeat;
|
|
}
|
|
|
|
pages[ret] = page;
|
|
if (++ret == nr_pages)
|
|
break;
|
|
}
|
|
|
|
rcu_read_unlock();
|
|
return ret;
|
|
}
|
|
|
|
/**
|
|
* find_get_pages_contig - gang contiguous pagecache lookup
|
|
* @mapping: The address_space to search
|
|
* @index: The starting page index
|
|
* @nr_pages: The maximum number of pages
|
|
* @pages: Where the resulting pages are placed
|
|
*
|
|
* find_get_pages_contig() works exactly like find_get_pages(), except
|
|
* that the returned number of pages are guaranteed to be contiguous.
|
|
*
|
|
* find_get_pages_contig() returns the number of pages which were found.
|
|
*/
|
|
unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
|
|
unsigned int nr_pages, struct page **pages)
|
|
{
|
|
struct radix_tree_iter iter;
|
|
void **slot;
|
|
unsigned int ret = 0;
|
|
|
|
if (unlikely(!nr_pages))
|
|
return 0;
|
|
|
|
rcu_read_lock();
|
|
restart:
|
|
radix_tree_for_each_contig(slot, &mapping->page_tree, &iter, index) {
|
|
struct page *page;
|
|
repeat:
|
|
page = radix_tree_deref_slot(slot);
|
|
/* The hole, there no reason to continue */
|
|
if (unlikely(!page))
|
|
break;
|
|
|
|
if (radix_tree_exception(page)) {
|
|
if (radix_tree_deref_retry(page)) {
|
|
/*
|
|
* Transient condition which can only trigger
|
|
* when entry at index 0 moves out of or back
|
|
* to root: none yet gotten, safe to restart.
|
|
*/
|
|
goto restart;
|
|
}
|
|
/*
|
|
* Otherwise, shmem/tmpfs must be storing a swap entry
|
|
* here as an exceptional entry: so stop looking for
|
|
* contiguous pages.
|
|
*/
|
|
break;
|
|
}
|
|
|
|
if (!page_cache_get_speculative(page))
|
|
goto repeat;
|
|
|
|
/* Has the page moved? */
|
|
if (unlikely(page != *slot)) {
|
|
page_cache_release(page);
|
|
goto repeat;
|
|
}
|
|
|
|
/*
|
|
* must check mapping and index after taking the ref.
|
|
* otherwise we can get both false positives and false
|
|
* negatives, which is just confusing to the caller.
|
|
*/
|
|
if (page->mapping == NULL || page->index != iter.index) {
|
|
page_cache_release(page);
|
|
break;
|
|
}
|
|
|
|
pages[ret] = page;
|
|
if (++ret == nr_pages)
|
|
break;
|
|
}
|
|
rcu_read_unlock();
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(find_get_pages_contig);
|
|
|
|
/**
|
|
* find_get_pages_tag - find and return pages that match @tag
|
|
* @mapping: the address_space to search
|
|
* @index: the starting page index
|
|
* @tag: the tag index
|
|
* @nr_pages: the maximum number of pages
|
|
* @pages: where the resulting pages are placed
|
|
*
|
|
* Like find_get_pages, except we only return pages which are tagged with
|
|
* @tag. We update @index to index the next page for the traversal.
|
|
*/
|
|
unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
|
|
int tag, unsigned int nr_pages, struct page **pages)
|
|
{
|
|
struct radix_tree_iter iter;
|
|
void **slot;
|
|
unsigned ret = 0;
|
|
|
|
if (unlikely(!nr_pages))
|
|
return 0;
|
|
|
|
rcu_read_lock();
|
|
restart:
|
|
radix_tree_for_each_tagged(slot, &mapping->page_tree,
|
|
&iter, *index, tag) {
|
|
struct page *page;
|
|
repeat:
|
|
page = radix_tree_deref_slot(slot);
|
|
if (unlikely(!page))
|
|
continue;
|
|
|
|
if (radix_tree_exception(page)) {
|
|
if (radix_tree_deref_retry(page)) {
|
|
/*
|
|
* Transient condition which can only trigger
|
|
* when entry at index 0 moves out of or back
|
|
* to root: none yet gotten, safe to restart.
|
|
*/
|
|
goto restart;
|
|
}
|
|
/*
|
|
* This function is never used on a shmem/tmpfs
|
|
* mapping, so a swap entry won't be found here.
|
|
*/
|
|
BUG();
|
|
}
|
|
|
|
if (!page_cache_get_speculative(page))
|
|
goto repeat;
|
|
|
|
/* Has the page moved? */
|
|
if (unlikely(page != *slot)) {
|
|
page_cache_release(page);
|
|
goto repeat;
|
|
}
|
|
|
|
pages[ret] = page;
|
|
if (++ret == nr_pages)
|
|
break;
|
|
}
|
|
|
|
rcu_read_unlock();
|
|
|
|
if (ret)
|
|
*index = pages[ret - 1]->index + 1;
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(find_get_pages_tag);
|
|
|
|
/**
|
|
* grab_cache_page_nowait - returns locked page at given index in given cache
|
|
* @mapping: target address_space
|
|
* @index: the page index
|
|
*
|
|
* Same as grab_cache_page(), but do not wait if the page is unavailable.
|
|
* This is intended for speculative data generators, where the data can
|
|
* be regenerated if the page couldn't be grabbed. This routine should
|
|
* be safe to call while holding the lock for another page.
|
|
*
|
|
* Clear __GFP_FS when allocating the page to avoid recursion into the fs
|
|
* and deadlock against the caller's locked page.
|
|
*/
|
|
struct page *
|
|
grab_cache_page_nowait(struct address_space *mapping, pgoff_t index)
|
|
{
|
|
struct page *page = find_get_page(mapping, index);
|
|
|
|
if (page) {
|
|
if (trylock_page(page))
|
|
return page;
|
|
page_cache_release(page);
|
|
return NULL;
|
|
}
|
|
page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS);
|
|
if (page && add_to_page_cache_lru(page, mapping, index, GFP_NOFS)) {
|
|
page_cache_release(page);
|
|
page = NULL;
|
|
}
|
|
return page;
|
|
}
|
|
EXPORT_SYMBOL(grab_cache_page_nowait);
|
|
|
|
/*
|
|
* CD/DVDs are error prone. When a medium error occurs, the driver may fail
|
|
* a _large_ part of the i/o request. Imagine the worst scenario:
|
|
*
|
|
* ---R__________________________________________B__________
|
|
* ^ reading here ^ bad block(assume 4k)
|
|
*
|
|
* read(R) => miss => readahead(R...B) => media error => frustrating retries
|
|
* => failing the whole request => read(R) => read(R+1) =>
|
|
* readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
|
|
* readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
|
|
* readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
|
|
*
|
|
* It is going insane. Fix it by quickly scaling down the readahead size.
|
|
*/
|
|
static void shrink_readahead_size_eio(struct file *filp,
|
|
struct file_ra_state *ra)
|
|
{
|
|
ra->ra_pages /= 4;
|
|
}
|
|
|
|
/**
|
|
* do_generic_file_read - generic file read routine
|
|
* @filp: the file to read
|
|
* @ppos: current file position
|
|
* @desc: read_descriptor
|
|
* @actor: read method
|
|
*
|
|
* This is a generic file read routine, and uses the
|
|
* mapping->a_ops->readpage() function for the actual low-level stuff.
|
|
*
|
|
* This is really ugly. But the goto's actually try to clarify some
|
|
* of the logic when it comes to error handling etc.
|
|
*/
|
|
static void do_generic_file_read(struct file *filp, loff_t *ppos,
|
|
read_descriptor_t *desc, read_actor_t actor)
|
|
{
|
|
struct address_space *mapping = filp->f_mapping;
|
|
struct inode *inode = mapping->host;
|
|
struct file_ra_state *ra = &filp->f_ra;
|
|
pgoff_t index;
|
|
pgoff_t last_index;
|
|
pgoff_t prev_index;
|
|
unsigned long offset; /* offset into pagecache page */
|
|
unsigned int prev_offset;
|
|
int error;
|
|
|
|
index = *ppos >> PAGE_CACHE_SHIFT;
|
|
prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT;
|
|
prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1);
|
|
last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
|
|
offset = *ppos & ~PAGE_CACHE_MASK;
|
|
|
|
for (;;) {
|
|
struct page *page;
|
|
pgoff_t end_index;
|
|
loff_t isize;
|
|
unsigned long nr, ret;
|
|
|
|
cond_resched();
|
|
find_page:
|
|
page = find_get_page(mapping, index);
|
|
if (!page) {
|
|
page_cache_sync_readahead(mapping,
|
|
ra, filp,
|
|
index, last_index - index);
|
|
page = find_get_page(mapping, index);
|
|
if (unlikely(page == NULL))
|
|
goto no_cached_page;
|
|
}
|
|
if (PageReadahead(page)) {
|
|
page_cache_async_readahead(mapping,
|
|
ra, filp, page,
|
|
index, last_index - index);
|
|
}
|
|
if (!PageUptodate(page)) {
|
|
if (inode->i_blkbits == PAGE_CACHE_SHIFT ||
|
|
!mapping->a_ops->is_partially_uptodate)
|
|
goto page_not_up_to_date;
|
|
if (!trylock_page(page))
|
|
goto page_not_up_to_date;
|
|
/* Did it get truncated before we got the lock? */
|
|
if (!page->mapping)
|
|
goto page_not_up_to_date_locked;
|
|
if (!mapping->a_ops->is_partially_uptodate(page,
|
|
desc, offset))
|
|
goto page_not_up_to_date_locked;
|
|
unlock_page(page);
|
|
}
|
|
page_ok:
|
|
/*
|
|
* i_size must be checked after we know the page is Uptodate.
|
|
*
|
|
* Checking i_size after the check allows us to calculate
|
|
* the correct value for "nr", which means the zero-filled
|
|
* part of the page is not copied back to userspace (unless
|
|
* another truncate extends the file - this is desired though).
|
|
*/
|
|
|
|
isize = i_size_read(inode);
|
|
end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
|
|
if (unlikely(!isize || index > end_index)) {
|
|
page_cache_release(page);
|
|
goto out;
|
|
}
|
|
|
|
/* nr is the maximum number of bytes to copy from this page */
|
|
nr = PAGE_CACHE_SIZE;
|
|
if (index == end_index) {
|
|
nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
|
|
if (nr <= offset) {
|
|
page_cache_release(page);
|
|
goto out;
|
|
}
|
|
}
|
|
nr = nr - offset;
|
|
|
|
/* If users can be writing to this page using arbitrary
|
|
* virtual addresses, take care about potential aliasing
|
|
* before reading the page on the kernel side.
|
|
*/
|
|
if (mapping_writably_mapped(mapping))
|
|
flush_dcache_page(page);
|
|
|
|
/*
|
|
* When a sequential read accesses a page several times,
|
|
* only mark it as accessed the first time.
|
|
*/
|
|
if (prev_index != index || offset != prev_offset)
|
|
mark_page_accessed(page);
|
|
prev_index = index;
|
|
|
|
/*
|
|
* Ok, we have the page, and it's up-to-date, so
|
|
* now we can copy it to user space...
|
|
*
|
|
* The actor routine returns how many bytes were actually used..
|
|
* NOTE! This may not be the same as how much of a user buffer
|
|
* we filled up (we may be padding etc), so we can only update
|
|
* "pos" here (the actor routine has to update the user buffer
|
|
* pointers and the remaining count).
|
|
*/
|
|
ret = actor(desc, page, offset, nr);
|
|
offset += ret;
|
|
index += offset >> PAGE_CACHE_SHIFT;
|
|
offset &= ~PAGE_CACHE_MASK;
|
|
prev_offset = offset;
|
|
|
|
page_cache_release(page);
|
|
if (ret == nr && desc->count)
|
|
continue;
|
|
goto out;
|
|
|
|
page_not_up_to_date:
|
|
/* Get exclusive access to the page ... */
|
|
error = lock_page_killable(page);
|
|
if (unlikely(error))
|
|
goto readpage_error;
|
|
|
|
page_not_up_to_date_locked:
|
|
/* Did it get truncated before we got the lock? */
|
|
if (!page->mapping) {
|
|
unlock_page(page);
|
|
page_cache_release(page);
|
|
continue;
|
|
}
|
|
|
|
/* Did somebody else fill it already? */
|
|
if (PageUptodate(page)) {
|
|
unlock_page(page);
|
|
goto page_ok;
|
|
}
|
|
|
|
readpage:
|
|
/*
|
|
* A previous I/O error may have been due to temporary
|
|
* failures, eg. multipath errors.
|
|
* PG_error will be set again if readpage fails.
|
|
*/
|
|
ClearPageError(page);
|
|
/* Start the actual read. The read will unlock the page. */
|
|
error = mapping->a_ops->readpage(filp, page);
|
|
|
|
if (unlikely(error)) {
|
|
if (error == AOP_TRUNCATED_PAGE) {
|
|
page_cache_release(page);
|
|
goto find_page;
|
|
}
|
|
goto readpage_error;
|
|
}
|
|
|
|
if (!PageUptodate(page)) {
|
|
error = lock_page_killable(page);
|
|
if (unlikely(error))
|
|
goto readpage_error;
|
|
if (!PageUptodate(page)) {
|
|
if (page->mapping == NULL) {
|
|
/*
|
|
* invalidate_mapping_pages got it
|
|
*/
|
|
unlock_page(page);
|
|
page_cache_release(page);
|
|
goto find_page;
|
|
}
|
|
unlock_page(page);
|
|
shrink_readahead_size_eio(filp, ra);
|
|
error = -EIO;
|
|
goto readpage_error;
|
|
}
|
|
unlock_page(page);
|
|
}
|
|
|
|
goto page_ok;
|
|
|
|
readpage_error:
|
|
/* UHHUH! A synchronous read error occurred. Report it */
|
|
desc->error = error;
|
|
page_cache_release(page);
|
|
goto out;
|
|
|
|
no_cached_page:
|
|
/*
|
|
* Ok, it wasn't cached, so we need to create a new
|
|
* page..
|
|
*/
|
|
page = page_cache_alloc_cold(mapping);
|
|
if (!page) {
|
|
desc->error = -ENOMEM;
|
|
goto out;
|
|
}
|
|
error = add_to_page_cache_lru(page, mapping,
|
|
index, GFP_KERNEL);
|
|
if (error) {
|
|
page_cache_release(page);
|
|
if (error == -EEXIST)
|
|
goto find_page;
|
|
desc->error = error;
|
|
goto out;
|
|
}
|
|
goto readpage;
|
|
}
|
|
|
|
out:
|
|
ra->prev_pos = prev_index;
|
|
ra->prev_pos <<= PAGE_CACHE_SHIFT;
|
|
ra->prev_pos |= prev_offset;
|
|
|
|
*ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset;
|
|
file_accessed(filp);
|
|
}
|
|
|
|
int file_read_actor(read_descriptor_t *desc, struct page *page,
|
|
unsigned long offset, unsigned long size)
|
|
{
|
|
char *kaddr;
|
|
unsigned long left, count = desc->count;
|
|
|
|
if (size > count)
|
|
size = count;
|
|
|
|
/*
|
|
* Faults on the destination of a read are common, so do it before
|
|
* taking the kmap.
|
|
*/
|
|
if (!fault_in_pages_writeable(desc->arg.buf, size)) {
|
|
kaddr = kmap_atomic(page);
|
|
left = __copy_to_user_inatomic(desc->arg.buf,
|
|
kaddr + offset, size);
|
|
kunmap_atomic(kaddr);
|
|
if (left == 0)
|
|
goto success;
|
|
}
|
|
|
|
/* Do it the slow way */
|
|
kaddr = kmap(page);
|
|
left = __copy_to_user(desc->arg.buf, kaddr + offset, size);
|
|
kunmap(page);
|
|
|
|
if (left) {
|
|
size -= left;
|
|
desc->error = -EFAULT;
|
|
}
|
|
success:
|
|
desc->count = count - size;
|
|
desc->written += size;
|
|
desc->arg.buf += size;
|
|
return size;
|
|
}
|
|
|
|
/*
|
|
* Performs necessary checks before doing a write
|
|
* @iov: io vector request
|
|
* @nr_segs: number of segments in the iovec
|
|
* @count: number of bytes to write
|
|
* @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE
|
|
*
|
|
* Adjust number of segments and amount of bytes to write (nr_segs should be
|
|
* properly initialized first). Returns appropriate error code that caller
|
|
* should return or zero in case that write should be allowed.
|
|
*/
|
|
int generic_segment_checks(const struct iovec *iov,
|
|
unsigned long *nr_segs, size_t *count, int access_flags)
|
|
{
|
|
unsigned long seg;
|
|
size_t cnt = 0;
|
|
for (seg = 0; seg < *nr_segs; seg++) {
|
|
const struct iovec *iv = &iov[seg];
|
|
|
|
/*
|
|
* If any segment has a negative length, or the cumulative
|
|
* length ever wraps negative then return -EINVAL.
|
|
*/
|
|
cnt += iv->iov_len;
|
|
if (unlikely((ssize_t)(cnt|iv->iov_len) < 0))
|
|
return -EINVAL;
|
|
if (access_ok(access_flags, iv->iov_base, iv->iov_len))
|
|
continue;
|
|
if (seg == 0)
|
|
return -EFAULT;
|
|
*nr_segs = seg;
|
|
cnt -= iv->iov_len; /* This segment is no good */
|
|
break;
|
|
}
|
|
*count = cnt;
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(generic_segment_checks);
|
|
|
|
/**
|
|
* generic_file_aio_read - generic filesystem read routine
|
|
* @iocb: kernel I/O control block
|
|
* @iov: io vector request
|
|
* @nr_segs: number of segments in the iovec
|
|
* @pos: current file position
|
|
*
|
|
* This is the "read()" routine for all filesystems
|
|
* that can use the page cache directly.
|
|
*/
|
|
ssize_t
|
|
generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
|
|
unsigned long nr_segs, loff_t pos)
|
|
{
|
|
struct file *filp = iocb->ki_filp;
|
|
ssize_t retval;
|
|
unsigned long seg = 0;
|
|
size_t count;
|
|
loff_t *ppos = &iocb->ki_pos;
|
|
|
|
count = 0;
|
|
retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
|
|
if (retval)
|
|
return retval;
|
|
|
|
/* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
|
|
if (filp->f_flags & O_DIRECT) {
|
|
loff_t size;
|
|
struct address_space *mapping;
|
|
struct inode *inode;
|
|
|
|
mapping = filp->f_mapping;
|
|
inode = mapping->host;
|
|
if (!count)
|
|
goto out; /* skip atime */
|
|
size = i_size_read(inode);
|
|
if (pos < size) {
|
|
retval = filemap_write_and_wait_range(mapping, pos,
|
|
pos + iov_length(iov, nr_segs) - 1);
|
|
if (!retval) {
|
|
retval = mapping->a_ops->direct_IO(READ, iocb,
|
|
iov, pos, nr_segs);
|
|
}
|
|
if (retval > 0) {
|
|
*ppos = pos + retval;
|
|
count -= retval;
|
|
}
|
|
|
|
/*
|
|
* Btrfs can have a short DIO read if we encounter
|
|
* compressed extents, so if there was an error, or if
|
|
* we've already read everything we wanted to, or if
|
|
* there was a short read because we hit EOF, go ahead
|
|
* and return. Otherwise fallthrough to buffered io for
|
|
* the rest of the read.
|
|
*/
|
|
if (retval < 0 || !count || *ppos >= size) {
|
|
file_accessed(filp);
|
|
goto out;
|
|
}
|
|
}
|
|
}
|
|
|
|
count = retval;
|
|
for (seg = 0; seg < nr_segs; seg++) {
|
|
read_descriptor_t desc;
|
|
loff_t offset = 0;
|
|
|
|
/*
|
|
* If we did a short DIO read we need to skip the section of the
|
|
* iov that we've already read data into.
|
|
*/
|
|
if (count) {
|
|
if (count > iov[seg].iov_len) {
|
|
count -= iov[seg].iov_len;
|
|
continue;
|
|
}
|
|
offset = count;
|
|
count = 0;
|
|
}
|
|
|
|
desc.written = 0;
|
|
desc.arg.buf = iov[seg].iov_base + offset;
|
|
desc.count = iov[seg].iov_len - offset;
|
|
if (desc.count == 0)
|
|
continue;
|
|
desc.error = 0;
|
|
do_generic_file_read(filp, ppos, &desc, file_read_actor);
|
|
retval += desc.written;
|
|
if (desc.error) {
|
|
retval = retval ?: desc.error;
|
|
break;
|
|
}
|
|
if (desc.count > 0)
|
|
break;
|
|
}
|
|
out:
|
|
return retval;
|
|
}
|
|
EXPORT_SYMBOL(generic_file_aio_read);
|
|
|
|
#ifdef CONFIG_MMU
|
|
/**
|
|
* page_cache_read - adds requested page to the page cache if not already there
|
|
* @file: file to read
|
|
* @offset: page index
|
|
*
|
|
* This adds the requested page to the page cache if it isn't already there,
|
|
* and schedules an I/O to read in its contents from disk.
|
|
*/
|
|
static int page_cache_read(struct file *file, pgoff_t offset)
|
|
{
|
|
struct address_space *mapping = file->f_mapping;
|
|
struct page *page;
|
|
int ret;
|
|
|
|
do {
|
|
page = page_cache_alloc_cold(mapping);
|
|
if (!page)
|
|
return -ENOMEM;
|
|
|
|
ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL);
|
|
if (ret == 0)
|
|
ret = mapping->a_ops->readpage(file, page);
|
|
else if (ret == -EEXIST)
|
|
ret = 0; /* losing race to add is OK */
|
|
|
|
page_cache_release(page);
|
|
|
|
} while (ret == AOP_TRUNCATED_PAGE);
|
|
|
|
return ret;
|
|
}
|
|
|
|
#define MMAP_LOTSAMISS (100)
|
|
|
|
/*
|
|
* Synchronous readahead happens when we don't even find
|
|
* a page in the page cache at all.
|
|
*/
|
|
static void do_sync_mmap_readahead(struct vm_area_struct *vma,
|
|
struct file_ra_state *ra,
|
|
struct file *file,
|
|
pgoff_t offset)
|
|
{
|
|
unsigned long ra_pages;
|
|
struct address_space *mapping = file->f_mapping;
|
|
|
|
/* If we don't want any read-ahead, don't bother */
|
|
if (vma->vm_flags & VM_RAND_READ)
|
|
return;
|
|
if (!ra->ra_pages)
|
|
return;
|
|
|
|
if (vma->vm_flags & VM_SEQ_READ) {
|
|
page_cache_sync_readahead(mapping, ra, file, offset,
|
|
ra->ra_pages);
|
|
return;
|
|
}
|
|
|
|
/* Avoid banging the cache line if not needed */
|
|
if (ra->mmap_miss < MMAP_LOTSAMISS * 10)
|
|
ra->mmap_miss++;
|
|
|
|
/*
|
|
* Do we miss much more than hit in this file? If so,
|
|
* stop bothering with read-ahead. It will only hurt.
|
|
*/
|
|
if (ra->mmap_miss > MMAP_LOTSAMISS)
|
|
return;
|
|
|
|
/*
|
|
* mmap read-around
|
|
*/
|
|
ra_pages = max_sane_readahead(ra->ra_pages);
|
|
ra->start = max_t(long, 0, offset - ra_pages / 2);
|
|
ra->size = ra_pages;
|
|
ra->async_size = ra_pages / 4;
|
|
ra_submit(ra, mapping, file);
|
|
}
|
|
|
|
/*
|
|
* Asynchronous readahead happens when we find the page and PG_readahead,
|
|
* so we want to possibly extend the readahead further..
|
|
*/
|
|
static void do_async_mmap_readahead(struct vm_area_struct *vma,
|
|
struct file_ra_state *ra,
|
|
struct file *file,
|
|
struct page *page,
|
|
pgoff_t offset)
|
|
{
|
|
struct address_space *mapping = file->f_mapping;
|
|
|
|
/* If we don't want any read-ahead, don't bother */
|
|
if (vma->vm_flags & VM_RAND_READ)
|
|
return;
|
|
if (ra->mmap_miss > 0)
|
|
ra->mmap_miss--;
|
|
if (PageReadahead(page))
|
|
page_cache_async_readahead(mapping, ra, file,
|
|
page, offset, ra->ra_pages);
|
|
}
|
|
|
|
/**
|
|
* filemap_fault - read in file data for page fault handling
|
|
* @vma: vma in which the fault was taken
|
|
* @vmf: struct vm_fault containing details of the fault
|
|
*
|
|
* filemap_fault() is invoked via the vma operations vector for a
|
|
* mapped memory region to read in file data during a page fault.
|
|
*
|
|
* The goto's are kind of ugly, but this streamlines the normal case of having
|
|
* it in the page cache, and handles the special cases reasonably without
|
|
* having a lot of duplicated code.
|
|
*/
|
|
int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
|
|
{
|
|
int error;
|
|
struct file *file = vma->vm_file;
|
|
struct address_space *mapping = file->f_mapping;
|
|
struct file_ra_state *ra = &file->f_ra;
|
|
struct inode *inode = mapping->host;
|
|
pgoff_t offset = vmf->pgoff;
|
|
struct page *page;
|
|
pgoff_t size;
|
|
int ret = 0;
|
|
|
|
size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
|
|
if (offset >= size)
|
|
return VM_FAULT_SIGBUS;
|
|
|
|
/*
|
|
* Do we have something in the page cache already?
|
|
*/
|
|
page = find_get_page(mapping, offset);
|
|
if (likely(page) && !(vmf->flags & FAULT_FLAG_TRIED)) {
|
|
/*
|
|
* We found the page, so try async readahead before
|
|
* waiting for the lock.
|
|
*/
|
|
do_async_mmap_readahead(vma, ra, file, page, offset);
|
|
} else if (!page) {
|
|
/* No page in the page cache at all */
|
|
do_sync_mmap_readahead(vma, ra, file, offset);
|
|
count_vm_event(PGMAJFAULT);
|
|
mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
|
|
ret = VM_FAULT_MAJOR;
|
|
retry_find:
|
|
page = find_get_page(mapping, offset);
|
|
if (!page)
|
|
goto no_cached_page;
|
|
}
|
|
|
|
if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) {
|
|
page_cache_release(page);
|
|
return ret | VM_FAULT_RETRY;
|
|
}
|
|
|
|
/* Did it get truncated? */
|
|
if (unlikely(page->mapping != mapping)) {
|
|
unlock_page(page);
|
|
put_page(page);
|
|
goto retry_find;
|
|
}
|
|
VM_BUG_ON(page->index != offset);
|
|
|
|
/*
|
|
* We have a locked page in the page cache, now we need to check
|
|
* that it's up-to-date. If not, it is going to be due to an error.
|
|
*/
|
|
if (unlikely(!PageUptodate(page)))
|
|
goto page_not_uptodate;
|
|
|
|
/*
|
|
* Found the page and have a reference on it.
|
|
* We must recheck i_size under page lock.
|
|
*/
|
|
size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
|
|
if (unlikely(offset >= size)) {
|
|
unlock_page(page);
|
|
page_cache_release(page);
|
|
return VM_FAULT_SIGBUS;
|
|
}
|
|
|
|
vmf->page = page;
|
|
return ret | VM_FAULT_LOCKED;
|
|
|
|
no_cached_page:
|
|
/*
|
|
* We're only likely to ever get here if MADV_RANDOM is in
|
|
* effect.
|
|
*/
|
|
error = page_cache_read(file, offset);
|
|
|
|
/*
|
|
* The page we want has now been added to the page cache.
|
|
* In the unlikely event that someone removed it in the
|
|
* meantime, we'll just come back here and read it again.
|
|
*/
|
|
if (error >= 0)
|
|
goto retry_find;
|
|
|
|
/*
|
|
* An error return from page_cache_read can result if the
|
|
* system is low on memory, or a problem occurs while trying
|
|
* to schedule I/O.
|
|
*/
|
|
if (error == -ENOMEM)
|
|
return VM_FAULT_OOM;
|
|
return VM_FAULT_SIGBUS;
|
|
|
|
page_not_uptodate:
|
|
/*
|
|
* Umm, take care of errors if the page isn't up-to-date.
|
|
* Try to re-read it _once_. We do this synchronously,
|
|
* because there really aren't any performance issues here
|
|
* and we need to check for errors.
|
|
*/
|
|
ClearPageError(page);
|
|
error = mapping->a_ops->readpage(file, page);
|
|
if (!error) {
|
|
wait_on_page_locked(page);
|
|
if (!PageUptodate(page))
|
|
error = -EIO;
|
|
}
|
|
page_cache_release(page);
|
|
|
|
if (!error || error == AOP_TRUNCATED_PAGE)
|
|
goto retry_find;
|
|
|
|
/* Things didn't work out. Return zero to tell the mm layer so. */
|
|
shrink_readahead_size_eio(file, ra);
|
|
return VM_FAULT_SIGBUS;
|
|
}
|
|
EXPORT_SYMBOL(filemap_fault);
|
|
|
|
int filemap_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
|
|
{
|
|
struct page *page = vmf->page;
|
|
struct inode *inode = file_inode(vma->vm_file);
|
|
int ret = VM_FAULT_LOCKED;
|
|
|
|
sb_start_pagefault(inode->i_sb);
|
|
file_update_time(vma->vm_file);
|
|
lock_page(page);
|
|
if (page->mapping != inode->i_mapping) {
|
|
unlock_page(page);
|
|
ret = VM_FAULT_NOPAGE;
|
|
goto out;
|
|
}
|
|
/*
|
|
* We mark the page dirty already here so that when freeze is in
|
|
* progress, we are guaranteed that writeback during freezing will
|
|
* see the dirty page and writeprotect it again.
|
|
*/
|
|
set_page_dirty(page);
|
|
wait_for_stable_page(page);
|
|
out:
|
|
sb_end_pagefault(inode->i_sb);
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(filemap_page_mkwrite);
|
|
|
|
const struct vm_operations_struct generic_file_vm_ops = {
|
|
.fault = filemap_fault,
|
|
.page_mkwrite = filemap_page_mkwrite,
|
|
.remap_pages = generic_file_remap_pages,
|
|
};
|
|
|
|
/* This is used for a general mmap of a disk file */
|
|
|
|
int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
|
|
{
|
|
struct address_space *mapping = file->f_mapping;
|
|
|
|
if (!mapping->a_ops->readpage)
|
|
return -ENOEXEC;
|
|
file_accessed(file);
|
|
vma->vm_ops = &generic_file_vm_ops;
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* This is for filesystems which do not implement ->writepage.
|
|
*/
|
|
int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
|
|
{
|
|
if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
|
|
return -EINVAL;
|
|
return generic_file_mmap(file, vma);
|
|
}
|
|
#else
|
|
int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
|
|
{
|
|
return -ENOSYS;
|
|
}
|
|
int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
|
|
{
|
|
return -ENOSYS;
|
|
}
|
|
#endif /* CONFIG_MMU */
|
|
|
|
EXPORT_SYMBOL(generic_file_mmap);
|
|
EXPORT_SYMBOL(generic_file_readonly_mmap);
|
|
|
|
static struct page *__read_cache_page(struct address_space *mapping,
|
|
pgoff_t index,
|
|
int (*filler)(void *, struct page *),
|
|
void *data,
|
|
gfp_t gfp)
|
|
{
|
|
struct page *page;
|
|
int err;
|
|
repeat:
|
|
page = find_get_page(mapping, index);
|
|
if (!page) {
|
|
page = __page_cache_alloc(gfp | __GFP_COLD);
|
|
if (!page)
|
|
return ERR_PTR(-ENOMEM);
|
|
err = add_to_page_cache_lru(page, mapping, index, gfp);
|
|
if (unlikely(err)) {
|
|
page_cache_release(page);
|
|
if (err == -EEXIST)
|
|
goto repeat;
|
|
/* Presumably ENOMEM for radix tree node */
|
|
return ERR_PTR(err);
|
|
}
|
|
err = filler(data, page);
|
|
if (err < 0) {
|
|
page_cache_release(page);
|
|
page = ERR_PTR(err);
|
|
}
|
|
}
|
|
return page;
|
|
}
|
|
|
|
static struct page *do_read_cache_page(struct address_space *mapping,
|
|
pgoff_t index,
|
|
int (*filler)(void *, struct page *),
|
|
void *data,
|
|
gfp_t gfp)
|
|
|
|
{
|
|
struct page *page;
|
|
int err;
|
|
|
|
retry:
|
|
page = __read_cache_page(mapping, index, filler, data, gfp);
|
|
if (IS_ERR(page))
|
|
return page;
|
|
if (PageUptodate(page))
|
|
goto out;
|
|
|
|
lock_page(page);
|
|
if (!page->mapping) {
|
|
unlock_page(page);
|
|
page_cache_release(page);
|
|
goto retry;
|
|
}
|
|
if (PageUptodate(page)) {
|
|
unlock_page(page);
|
|
goto out;
|
|
}
|
|
err = filler(data, page);
|
|
if (err < 0) {
|
|
page_cache_release(page);
|
|
return ERR_PTR(err);
|
|
}
|
|
out:
|
|
mark_page_accessed(page);
|
|
return page;
|
|
}
|
|
|
|
/**
|
|
* read_cache_page_async - read into page cache, fill it if needed
|
|
* @mapping: the page's address_space
|
|
* @index: the page index
|
|
* @filler: function to perform the read
|
|
* @data: first arg to filler(data, page) function, often left as NULL
|
|
*
|
|
* Same as read_cache_page, but don't wait for page to become unlocked
|
|
* after submitting it to the filler.
|
|
*
|
|
* Read into the page cache. If a page already exists, and PageUptodate() is
|
|
* not set, try to fill the page but don't wait for it to become unlocked.
|
|
*
|
|
* If the page does not get brought uptodate, return -EIO.
|
|
*/
|
|
struct page *read_cache_page_async(struct address_space *mapping,
|
|
pgoff_t index,
|
|
int (*filler)(void *, struct page *),
|
|
void *data)
|
|
{
|
|
return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping));
|
|
}
|
|
EXPORT_SYMBOL(read_cache_page_async);
|
|
|
|
static struct page *wait_on_page_read(struct page *page)
|
|
{
|
|
if (!IS_ERR(page)) {
|
|
wait_on_page_locked(page);
|
|
if (!PageUptodate(page)) {
|
|
page_cache_release(page);
|
|
page = ERR_PTR(-EIO);
|
|
}
|
|
}
|
|
return page;
|
|
}
|
|
|
|
/**
|
|
* read_cache_page_gfp - read into page cache, using specified page allocation flags.
|
|
* @mapping: the page's address_space
|
|
* @index: the page index
|
|
* @gfp: the page allocator flags to use if allocating
|
|
*
|
|
* This is the same as "read_mapping_page(mapping, index, NULL)", but with
|
|
* any new page allocations done using the specified allocation flags.
|
|
*
|
|
* If the page does not get brought uptodate, return -EIO.
|
|
*/
|
|
struct page *read_cache_page_gfp(struct address_space *mapping,
|
|
pgoff_t index,
|
|
gfp_t gfp)
|
|
{
|
|
filler_t *filler = (filler_t *)mapping->a_ops->readpage;
|
|
|
|
return wait_on_page_read(do_read_cache_page(mapping, index, filler, NULL, gfp));
|
|
}
|
|
EXPORT_SYMBOL(read_cache_page_gfp);
|
|
|
|
/**
|
|
* read_cache_page - read into page cache, fill it if needed
|
|
* @mapping: the page's address_space
|
|
* @index: the page index
|
|
* @filler: function to perform the read
|
|
* @data: first arg to filler(data, page) function, often left as NULL
|
|
*
|
|
* Read into the page cache. If a page already exists, and PageUptodate() is
|
|
* not set, try to fill the page then wait for it to become unlocked.
|
|
*
|
|
* If the page does not get brought uptodate, return -EIO.
|
|
*/
|
|
struct page *read_cache_page(struct address_space *mapping,
|
|
pgoff_t index,
|
|
int (*filler)(void *, struct page *),
|
|
void *data)
|
|
{
|
|
return wait_on_page_read(read_cache_page_async(mapping, index, filler, data));
|
|
}
|
|
EXPORT_SYMBOL(read_cache_page);
|
|
|
|
static size_t __iovec_copy_from_user_inatomic(char *vaddr,
|
|
const struct iovec *iov, size_t base, size_t bytes)
|
|
{
|
|
size_t copied = 0, left = 0;
|
|
|
|
while (bytes) {
|
|
char __user *buf = iov->iov_base + base;
|
|
int copy = min(bytes, iov->iov_len - base);
|
|
|
|
base = 0;
|
|
left = __copy_from_user_inatomic(vaddr, buf, copy);
|
|
copied += copy;
|
|
bytes -= copy;
|
|
vaddr += copy;
|
|
iov++;
|
|
|
|
if (unlikely(left))
|
|
break;
|
|
}
|
|
return copied - left;
|
|
}
|
|
|
|
/*
|
|
* Copy as much as we can into the page and return the number of bytes which
|
|
* were successfully copied. If a fault is encountered then return the number of
|
|
* bytes which were copied.
|
|
*/
|
|
size_t iov_iter_copy_from_user_atomic(struct page *page,
|
|
struct iov_iter *i, unsigned long offset, size_t bytes)
|
|
{
|
|
char *kaddr;
|
|
size_t copied;
|
|
|
|
BUG_ON(!in_atomic());
|
|
kaddr = kmap_atomic(page);
|
|
if (likely(i->nr_segs == 1)) {
|
|
int left;
|
|
char __user *buf = i->iov->iov_base + i->iov_offset;
|
|
left = __copy_from_user_inatomic(kaddr + offset, buf, bytes);
|
|
copied = bytes - left;
|
|
} else {
|
|
copied = __iovec_copy_from_user_inatomic(kaddr + offset,
|
|
i->iov, i->iov_offset, bytes);
|
|
}
|
|
kunmap_atomic(kaddr);
|
|
|
|
return copied;
|
|
}
|
|
EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
|
|
|
|
/*
|
|
* This has the same sideeffects and return value as
|
|
* iov_iter_copy_from_user_atomic().
|
|
* The difference is that it attempts to resolve faults.
|
|
* Page must not be locked.
|
|
*/
|
|
size_t iov_iter_copy_from_user(struct page *page,
|
|
struct iov_iter *i, unsigned long offset, size_t bytes)
|
|
{
|
|
char *kaddr;
|
|
size_t copied;
|
|
|
|
kaddr = kmap(page);
|
|
if (likely(i->nr_segs == 1)) {
|
|
int left;
|
|
char __user *buf = i->iov->iov_base + i->iov_offset;
|
|
left = __copy_from_user(kaddr + offset, buf, bytes);
|
|
copied = bytes - left;
|
|
} else {
|
|
copied = __iovec_copy_from_user_inatomic(kaddr + offset,
|
|
i->iov, i->iov_offset, bytes);
|
|
}
|
|
kunmap(page);
|
|
return copied;
|
|
}
|
|
EXPORT_SYMBOL(iov_iter_copy_from_user);
|
|
|
|
void iov_iter_advance(struct iov_iter *i, size_t bytes)
|
|
{
|
|
BUG_ON(i->count < bytes);
|
|
|
|
if (likely(i->nr_segs == 1)) {
|
|
i->iov_offset += bytes;
|
|
i->count -= bytes;
|
|
} else {
|
|
const struct iovec *iov = i->iov;
|
|
size_t base = i->iov_offset;
|
|
unsigned long nr_segs = i->nr_segs;
|
|
|
|
/*
|
|
* The !iov->iov_len check ensures we skip over unlikely
|
|
* zero-length segments (without overruning the iovec).
|
|
*/
|
|
while (bytes || unlikely(i->count && !iov->iov_len)) {
|
|
int copy;
|
|
|
|
copy = min(bytes, iov->iov_len - base);
|
|
BUG_ON(!i->count || i->count < copy);
|
|
i->count -= copy;
|
|
bytes -= copy;
|
|
base += copy;
|
|
if (iov->iov_len == base) {
|
|
iov++;
|
|
nr_segs--;
|
|
base = 0;
|
|
}
|
|
}
|
|
i->iov = iov;
|
|
i->iov_offset = base;
|
|
i->nr_segs = nr_segs;
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(iov_iter_advance);
|
|
|
|
/*
|
|
* Fault in the first iovec of the given iov_iter, to a maximum length
|
|
* of bytes. Returns 0 on success, or non-zero if the memory could not be
|
|
* accessed (ie. because it is an invalid address).
|
|
*
|
|
* writev-intensive code may want this to prefault several iovecs -- that
|
|
* would be possible (callers must not rely on the fact that _only_ the
|
|
* first iovec will be faulted with the current implementation).
|
|
*/
|
|
int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
|
|
{
|
|
char __user *buf = i->iov->iov_base + i->iov_offset;
|
|
bytes = min(bytes, i->iov->iov_len - i->iov_offset);
|
|
return fault_in_pages_readable(buf, bytes);
|
|
}
|
|
EXPORT_SYMBOL(iov_iter_fault_in_readable);
|
|
|
|
/*
|
|
* Return the count of just the current iov_iter segment.
|
|
*/
|
|
size_t iov_iter_single_seg_count(const struct iov_iter *i)
|
|
{
|
|
const struct iovec *iov = i->iov;
|
|
if (i->nr_segs == 1)
|
|
return i->count;
|
|
else
|
|
return min(i->count, iov->iov_len - i->iov_offset);
|
|
}
|
|
EXPORT_SYMBOL(iov_iter_single_seg_count);
|
|
|
|
/*
|
|
* Performs necessary checks before doing a write
|
|
*
|
|
* Can adjust writing position or amount of bytes to write.
|
|
* Returns appropriate error code that caller should return or
|
|
* zero in case that write should be allowed.
|
|
*/
|
|
inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk)
|
|
{
|
|
struct inode *inode = file->f_mapping->host;
|
|
unsigned long limit = rlimit(RLIMIT_FSIZE);
|
|
|
|
if (unlikely(*pos < 0))
|
|
return -EINVAL;
|
|
|
|
if (!isblk) {
|
|
/* FIXME: this is for backwards compatibility with 2.4 */
|
|
if (file->f_flags & O_APPEND)
|
|
*pos = i_size_read(inode);
|
|
|
|
if (limit != RLIM_INFINITY) {
|
|
if (*pos >= limit) {
|
|
send_sig(SIGXFSZ, current, 0);
|
|
return -EFBIG;
|
|
}
|
|
if (*count > limit - (typeof(limit))*pos) {
|
|
*count = limit - (typeof(limit))*pos;
|
|
}
|
|
}
|
|
}
|
|
|
|
/*
|
|
* LFS rule
|
|
*/
|
|
if (unlikely(*pos + *count > MAX_NON_LFS &&
|
|
!(file->f_flags & O_LARGEFILE))) {
|
|
if (*pos >= MAX_NON_LFS) {
|
|
return -EFBIG;
|
|
}
|
|
if (*count > MAX_NON_LFS - (unsigned long)*pos) {
|
|
*count = MAX_NON_LFS - (unsigned long)*pos;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Are we about to exceed the fs block limit ?
|
|
*
|
|
* If we have written data it becomes a short write. If we have
|
|
* exceeded without writing data we send a signal and return EFBIG.
|
|
* Linus frestrict idea will clean these up nicely..
|
|
*/
|
|
if (likely(!isblk)) {
|
|
if (unlikely(*pos >= inode->i_sb->s_maxbytes)) {
|
|
if (*count || *pos > inode->i_sb->s_maxbytes) {
|
|
return -EFBIG;
|
|
}
|
|
/* zero-length writes at ->s_maxbytes are OK */
|
|
}
|
|
|
|
if (unlikely(*pos + *count > inode->i_sb->s_maxbytes))
|
|
*count = inode->i_sb->s_maxbytes - *pos;
|
|
} else {
|
|
#ifdef CONFIG_BLOCK
|
|
loff_t isize;
|
|
if (bdev_read_only(I_BDEV(inode)))
|
|
return -EPERM;
|
|
isize = i_size_read(inode);
|
|
if (*pos >= isize) {
|
|
if (*count || *pos > isize)
|
|
return -ENOSPC;
|
|
}
|
|
|
|
if (*pos + *count > isize)
|
|
*count = isize - *pos;
|
|
#else
|
|
return -EPERM;
|
|
#endif
|
|
}
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(generic_write_checks);
|
|
|
|
int pagecache_write_begin(struct file *file, struct address_space *mapping,
|
|
loff_t pos, unsigned len, unsigned flags,
|
|
struct page **pagep, void **fsdata)
|
|
{
|
|
const struct address_space_operations *aops = mapping->a_ops;
|
|
|
|
return aops->write_begin(file, mapping, pos, len, flags,
|
|
pagep, fsdata);
|
|
}
|
|
EXPORT_SYMBOL(pagecache_write_begin);
|
|
|
|
int pagecache_write_end(struct file *file, struct address_space *mapping,
|
|
loff_t pos, unsigned len, unsigned copied,
|
|
struct page *page, void *fsdata)
|
|
{
|
|
const struct address_space_operations *aops = mapping->a_ops;
|
|
|
|
mark_page_accessed(page);
|
|
return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
|
|
}
|
|
EXPORT_SYMBOL(pagecache_write_end);
|
|
|
|
ssize_t
|
|
generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
|
|
unsigned long *nr_segs, loff_t pos, loff_t *ppos,
|
|
size_t count, size_t ocount)
|
|
{
|
|
struct file *file = iocb->ki_filp;
|
|
struct address_space *mapping = file->f_mapping;
|
|
struct inode *inode = mapping->host;
|
|
ssize_t written;
|
|
size_t write_len;
|
|
pgoff_t end;
|
|
|
|
if (count != ocount)
|
|
*nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count);
|
|
|
|
write_len = iov_length(iov, *nr_segs);
|
|
end = (pos + write_len - 1) >> PAGE_CACHE_SHIFT;
|
|
|
|
written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1);
|
|
if (written)
|
|
goto out;
|
|
|
|
/*
|
|
* After a write we want buffered reads to be sure to go to disk to get
|
|
* the new data. We invalidate clean cached page from the region we're
|
|
* about to write. We do this *before* the write so that we can return
|
|
* without clobbering -EIOCBQUEUED from ->direct_IO().
|
|
*/
|
|
if (mapping->nrpages) {
|
|
written = invalidate_inode_pages2_range(mapping,
|
|
pos >> PAGE_CACHE_SHIFT, end);
|
|
/*
|
|
* If a page can not be invalidated, return 0 to fall back
|
|
* to buffered write.
|
|
*/
|
|
if (written) {
|
|
if (written == -EBUSY)
|
|
return 0;
|
|
goto out;
|
|
}
|
|
}
|
|
|
|
written = mapping->a_ops->direct_IO(WRITE, iocb, iov, pos, *nr_segs);
|
|
|
|
/*
|
|
* Finally, try again to invalidate clean pages which might have been
|
|
* cached by non-direct readahead, or faulted in by get_user_pages()
|
|
* if the source of the write was an mmap'ed region of the file
|
|
* we're writing. Either one is a pretty crazy thing to do,
|
|
* so we don't support it 100%. If this invalidation
|
|
* fails, tough, the write still worked...
|
|
*/
|
|
if (mapping->nrpages) {
|
|
invalidate_inode_pages2_range(mapping,
|
|
pos >> PAGE_CACHE_SHIFT, end);
|
|
}
|
|
|
|
if (written > 0) {
|
|
pos += written;
|
|
if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
|
|
i_size_write(inode, pos);
|
|
mark_inode_dirty(inode);
|
|
}
|
|
*ppos = pos;
|
|
}
|
|
out:
|
|
return written;
|
|
}
|
|
EXPORT_SYMBOL(generic_file_direct_write);
|
|
|
|
/*
|
|
* Find or create a page at the given pagecache position. Return the locked
|
|
* page. This function is specifically for buffered writes.
|
|
*/
|
|
struct page *grab_cache_page_write_begin(struct address_space *mapping,
|
|
pgoff_t index, unsigned flags)
|
|
{
|
|
int status;
|
|
gfp_t gfp_mask;
|
|
struct page *page;
|
|
gfp_t gfp_notmask = 0;
|
|
|
|
gfp_mask = mapping_gfp_mask(mapping);
|
|
if (mapping_cap_account_dirty(mapping))
|
|
gfp_mask |= __GFP_WRITE;
|
|
if (flags & AOP_FLAG_NOFS)
|
|
gfp_notmask = __GFP_FS;
|
|
repeat:
|
|
page = find_lock_page(mapping, index);
|
|
if (page)
|
|
goto found;
|
|
|
|
page = __page_cache_alloc(gfp_mask & ~gfp_notmask);
|
|
if (!page)
|
|
return NULL;
|
|
status = add_to_page_cache_lru(page, mapping, index,
|
|
GFP_KERNEL & ~gfp_notmask);
|
|
if (unlikely(status)) {
|
|
page_cache_release(page);
|
|
if (status == -EEXIST)
|
|
goto repeat;
|
|
return NULL;
|
|
}
|
|
found:
|
|
wait_for_stable_page(page);
|
|
return page;
|
|
}
|
|
EXPORT_SYMBOL(grab_cache_page_write_begin);
|
|
|
|
static ssize_t generic_perform_write(struct file *file,
|
|
struct iov_iter *i, loff_t pos)
|
|
{
|
|
struct address_space *mapping = file->f_mapping;
|
|
const struct address_space_operations *a_ops = mapping->a_ops;
|
|
long status = 0;
|
|
ssize_t written = 0;
|
|
unsigned int flags = 0;
|
|
|
|
/*
|
|
* Copies from kernel address space cannot fail (NFSD is a big user).
|
|
*/
|
|
if (segment_eq(get_fs(), KERNEL_DS))
|
|
flags |= AOP_FLAG_UNINTERRUPTIBLE;
|
|
|
|
do {
|
|
struct page *page;
|
|
unsigned long offset; /* Offset into pagecache page */
|
|
unsigned long bytes; /* Bytes to write to page */
|
|
size_t copied; /* Bytes copied from user */
|
|
void *fsdata;
|
|
|
|
offset = (pos & (PAGE_CACHE_SIZE - 1));
|
|
bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
|
|
iov_iter_count(i));
|
|
|
|
again:
|
|
/*
|
|
* Bring in the user page that we will copy from _first_.
|
|
* Otherwise there's a nasty deadlock on copying from the
|
|
* same page as we're writing to, without it being marked
|
|
* up-to-date.
|
|
*
|
|
* Not only is this an optimisation, but it is also required
|
|
* to check that the address is actually valid, when atomic
|
|
* usercopies are used, below.
|
|
*/
|
|
if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
|
|
status = -EFAULT;
|
|
break;
|
|
}
|
|
|
|
status = a_ops->write_begin(file, mapping, pos, bytes, flags,
|
|
&page, &fsdata);
|
|
if (unlikely(status))
|
|
break;
|
|
|
|
if (mapping_writably_mapped(mapping))
|
|
flush_dcache_page(page);
|
|
|
|
pagefault_disable();
|
|
copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
|
|
pagefault_enable();
|
|
flush_dcache_page(page);
|
|
|
|
mark_page_accessed(page);
|
|
status = a_ops->write_end(file, mapping, pos, bytes, copied,
|
|
page, fsdata);
|
|
if (unlikely(status < 0))
|
|
break;
|
|
copied = status;
|
|
|
|
cond_resched();
|
|
|
|
iov_iter_advance(i, copied);
|
|
if (unlikely(copied == 0)) {
|
|
/*
|
|
* If we were unable to copy any data at all, we must
|
|
* fall back to a single segment length write.
|
|
*
|
|
* If we didn't fallback here, we could livelock
|
|
* because not all segments in the iov can be copied at
|
|
* once without a pagefault.
|
|
*/
|
|
bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
|
|
iov_iter_single_seg_count(i));
|
|
goto again;
|
|
}
|
|
pos += copied;
|
|
written += copied;
|
|
|
|
balance_dirty_pages_ratelimited(mapping);
|
|
if (fatal_signal_pending(current)) {
|
|
status = -EINTR;
|
|
break;
|
|
}
|
|
} while (iov_iter_count(i));
|
|
|
|
return written ? written : status;
|
|
}
|
|
|
|
ssize_t
|
|
generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
|
|
unsigned long nr_segs, loff_t pos, loff_t *ppos,
|
|
size_t count, ssize_t written)
|
|
{
|
|
struct file *file = iocb->ki_filp;
|
|
ssize_t status;
|
|
struct iov_iter i;
|
|
|
|
iov_iter_init(&i, iov, nr_segs, count, written);
|
|
status = generic_perform_write(file, &i, pos);
|
|
|
|
if (likely(status >= 0)) {
|
|
written += status;
|
|
*ppos = pos + status;
|
|
}
|
|
|
|
return written ? written : status;
|
|
}
|
|
EXPORT_SYMBOL(generic_file_buffered_write);
|
|
|
|
/**
|
|
* __generic_file_aio_write - write data to a file
|
|
* @iocb: IO state structure (file, offset, etc.)
|
|
* @iov: vector with data to write
|
|
* @nr_segs: number of segments in the vector
|
|
* @ppos: position where to write
|
|
*
|
|
* This function does all the work needed for actually writing data to a
|
|
* file. It does all basic checks, removes SUID from the file, updates
|
|
* modification times and calls proper subroutines depending on whether we
|
|
* do direct IO or a standard buffered write.
|
|
*
|
|
* It expects i_mutex to be grabbed unless we work on a block device or similar
|
|
* object which does not need locking at all.
|
|
*
|
|
* This function does *not* take care of syncing data in case of O_SYNC write.
|
|
* A caller has to handle it. This is mainly due to the fact that we want to
|
|
* avoid syncing under i_mutex.
|
|
*/
|
|
ssize_t __generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
|
|
unsigned long nr_segs, loff_t *ppos)
|
|
{
|
|
struct file *file = iocb->ki_filp;
|
|
struct address_space * mapping = file->f_mapping;
|
|
size_t ocount; /* original count */
|
|
size_t count; /* after file limit checks */
|
|
struct inode *inode = mapping->host;
|
|
loff_t pos;
|
|
ssize_t written;
|
|
ssize_t err;
|
|
|
|
ocount = 0;
|
|
err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);
|
|
if (err)
|
|
return err;
|
|
|
|
count = ocount;
|
|
pos = *ppos;
|
|
|
|
/* We can write back this queue in page reclaim */
|
|
current->backing_dev_info = mapping->backing_dev_info;
|
|
written = 0;
|
|
|
|
err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
|
|
if (err)
|
|
goto out;
|
|
|
|
if (count == 0)
|
|
goto out;
|
|
|
|
err = file_remove_suid(file);
|
|
if (err)
|
|
goto out;
|
|
|
|
err = file_update_time(file);
|
|
if (err)
|
|
goto out;
|
|
|
|
/* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
|
|
if (unlikely(file->f_flags & O_DIRECT)) {
|
|
loff_t endbyte;
|
|
ssize_t written_buffered;
|
|
|
|
written = generic_file_direct_write(iocb, iov, &nr_segs, pos,
|
|
ppos, count, ocount);
|
|
if (written < 0 || written == count)
|
|
goto out;
|
|
/*
|
|
* direct-io write to a hole: fall through to buffered I/O
|
|
* for completing the rest of the request.
|
|
*/
|
|
pos += written;
|
|
count -= written;
|
|
written_buffered = generic_file_buffered_write(iocb, iov,
|
|
nr_segs, pos, ppos, count,
|
|
written);
|
|
/*
|
|
* If generic_file_buffered_write() retuned a synchronous error
|
|
* then we want to return the number of bytes which were
|
|
* direct-written, or the error code if that was zero. Note
|
|
* that this differs from normal direct-io semantics, which
|
|
* will return -EFOO even if some bytes were written.
|
|
*/
|
|
if (written_buffered < 0) {
|
|
err = written_buffered;
|
|
goto out;
|
|
}
|
|
|
|
/*
|
|
* We need to ensure that the page cache pages are written to
|
|
* disk and invalidated to preserve the expected O_DIRECT
|
|
* semantics.
|
|
*/
|
|
endbyte = pos + written_buffered - written - 1;
|
|
err = filemap_write_and_wait_range(file->f_mapping, pos, endbyte);
|
|
if (err == 0) {
|
|
written = written_buffered;
|
|
invalidate_mapping_pages(mapping,
|
|
pos >> PAGE_CACHE_SHIFT,
|
|
endbyte >> PAGE_CACHE_SHIFT);
|
|
} else {
|
|
/*
|
|
* We don't know how much we wrote, so just return
|
|
* the number of bytes which were direct-written
|
|
*/
|
|
}
|
|
} else {
|
|
written = generic_file_buffered_write(iocb, iov, nr_segs,
|
|
pos, ppos, count, written);
|
|
}
|
|
out:
|
|
current->backing_dev_info = NULL;
|
|
return written ? written : err;
|
|
}
|
|
EXPORT_SYMBOL(__generic_file_aio_write);
|
|
|
|
/**
|
|
* generic_file_aio_write - write data to a file
|
|
* @iocb: IO state structure
|
|
* @iov: vector with data to write
|
|
* @nr_segs: number of segments in the vector
|
|
* @pos: position in file where to write
|
|
*
|
|
* This is a wrapper around __generic_file_aio_write() to be used by most
|
|
* filesystems. It takes care of syncing the file in case of O_SYNC file
|
|
* and acquires i_mutex as needed.
|
|
*/
|
|
ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
|
|
unsigned long nr_segs, loff_t pos)
|
|
{
|
|
struct file *file = iocb->ki_filp;
|
|
struct inode *inode = file->f_mapping->host;
|
|
ssize_t ret;
|
|
|
|
BUG_ON(iocb->ki_pos != pos);
|
|
|
|
mutex_lock(&inode->i_mutex);
|
|
ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
|
|
mutex_unlock(&inode->i_mutex);
|
|
|
|
if (ret > 0) {
|
|
ssize_t err;
|
|
|
|
err = generic_write_sync(file, pos, ret);
|
|
if (err < 0 && ret > 0)
|
|
ret = err;
|
|
}
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(generic_file_aio_write);
|
|
|
|
/**
|
|
* try_to_release_page() - release old fs-specific metadata on a page
|
|
*
|
|
* @page: the page which the kernel is trying to free
|
|
* @gfp_mask: memory allocation flags (and I/O mode)
|
|
*
|
|
* The address_space is to try to release any data against the page
|
|
* (presumably at page->private). If the release was successful, return `1'.
|
|
* Otherwise return zero.
|
|
*
|
|
* This may also be called if PG_fscache is set on a page, indicating that the
|
|
* page is known to the local caching routines.
|
|
*
|
|
* The @gfp_mask argument specifies whether I/O may be performed to release
|
|
* this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS).
|
|
*
|
|
*/
|
|
int try_to_release_page(struct page *page, gfp_t gfp_mask)
|
|
{
|
|
struct address_space * const mapping = page->mapping;
|
|
|
|
BUG_ON(!PageLocked(page));
|
|
if (PageWriteback(page))
|
|
return 0;
|
|
|
|
if (mapping && mapping->a_ops->releasepage)
|
|
return mapping->a_ops->releasepage(page, gfp_mask);
|
|
return try_to_free_buffers(page);
|
|
}
|
|
|
|
EXPORT_SYMBOL(try_to_release_page);
|