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![Nick Piggin](/assets/img/avatar_default.png)
Nonlinear mappings are (AFAIKS) simply a virtual memory concept that encodes the virtual address -> file offset differently from linear mappings. ->populate is a layering violation because the filesystem/pagecache code should need to know anything about the virtual memory mapping. The hitch here is that the ->nopage handler didn't pass down enough information (ie. pgoff). But it is more logical to pass pgoff rather than have the ->nopage function calculate it itself anyway (because that's a similar layering violation). Having the populate handler install the pte itself is likewise a nasty thing to be doing. This patch introduces a new fault handler that replaces ->nopage and ->populate and (later) ->nopfn. Most of the old mechanism is still in place so there is a lot of duplication and nice cleanups that can be removed if everyone switches over. The rationale for doing this in the first place is that nonlinear mappings are subject to the pagefault vs invalidate/truncate race too, and it seemed stupid to duplicate the synchronisation logic rather than just consolidate the two. After this patch, MAP_NONBLOCK no longer sets up ptes for pages present in pagecache. Seems like a fringe functionality anyway. NOPAGE_REFAULT is removed. This should be implemented with ->fault, and no users have hit mainline yet. [akpm@linux-foundation.org: cleanup] [randy.dunlap@oracle.com: doc. fixes for readahead] [akpm@linux-foundation.org: build fix] Signed-off-by: Nick Piggin <npiggin@suse.de> Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com> Cc: Mark Fasheh <mark.fasheh@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
464 lines
13 KiB
C
464 lines
13 KiB
C
/*
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* mm/truncate.c - code for taking down pages from address_spaces
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*
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* Copyright (C) 2002, Linus Torvalds
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*
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* 10Sep2002 akpm@zip.com.au
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* Initial version.
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*/
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#include <linux/kernel.h>
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#include <linux/mm.h>
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#include <linux/swap.h>
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#include <linux/module.h>
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#include <linux/pagemap.h>
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#include <linux/highmem.h>
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#include <linux/pagevec.h>
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#include <linux/task_io_accounting_ops.h>
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#include <linux/buffer_head.h> /* grr. try_to_release_page,
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do_invalidatepage */
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/**
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* do_invalidatepage - invalidate part of all of a page
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* @page: the page which is affected
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* @offset: the index of the truncation point
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*
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* do_invalidatepage() is called when all or part of the page has become
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* invalidated by a truncate operation.
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*
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* do_invalidatepage() does not have to release all buffers, but it must
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* ensure that no dirty buffer is left outside @offset and that no I/O
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* is underway against any of the blocks which are outside the truncation
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* point. Because the caller is about to free (and possibly reuse) those
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* blocks on-disk.
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*/
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void do_invalidatepage(struct page *page, unsigned long offset)
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{
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void (*invalidatepage)(struct page *, unsigned long);
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invalidatepage = page->mapping->a_ops->invalidatepage;
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#ifdef CONFIG_BLOCK
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if (!invalidatepage)
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invalidatepage = block_invalidatepage;
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#endif
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if (invalidatepage)
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(*invalidatepage)(page, offset);
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}
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static inline void truncate_partial_page(struct page *page, unsigned partial)
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{
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zero_user_page(page, partial, PAGE_CACHE_SIZE - partial, KM_USER0);
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if (PagePrivate(page))
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do_invalidatepage(page, partial);
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}
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/*
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* This cancels just the dirty bit on the kernel page itself, it
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* does NOT actually remove dirty bits on any mmap's that may be
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* around. It also leaves the page tagged dirty, so any sync
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* activity will still find it on the dirty lists, and in particular,
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* clear_page_dirty_for_io() will still look at the dirty bits in
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* the VM.
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*
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* Doing this should *normally* only ever be done when a page
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* is truncated, and is not actually mapped anywhere at all. However,
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* fs/buffer.c does this when it notices that somebody has cleaned
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* out all the buffers on a page without actually doing it through
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* the VM. Can you say "ext3 is horribly ugly"? Tought you could.
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*/
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void cancel_dirty_page(struct page *page, unsigned int account_size)
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{
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if (TestClearPageDirty(page)) {
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struct address_space *mapping = page->mapping;
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if (mapping && mapping_cap_account_dirty(mapping)) {
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dec_zone_page_state(page, NR_FILE_DIRTY);
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if (account_size)
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task_io_account_cancelled_write(account_size);
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}
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}
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}
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EXPORT_SYMBOL(cancel_dirty_page);
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/*
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* If truncate cannot remove the fs-private metadata from the page, the page
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* becomes anonymous. It will be left on the LRU and may even be mapped into
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* user pagetables if we're racing with filemap_fault().
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*
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* We need to bale out if page->mapping is no longer equal to the original
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* mapping. This happens a) when the VM reclaimed the page while we waited on
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* its lock, b) when a concurrent invalidate_mapping_pages got there first and
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* c) when tmpfs swizzles a page between a tmpfs inode and swapper_space.
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*/
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static void
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truncate_complete_page(struct address_space *mapping, struct page *page)
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{
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if (page->mapping != mapping)
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return;
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cancel_dirty_page(page, PAGE_CACHE_SIZE);
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if (PagePrivate(page))
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do_invalidatepage(page, 0);
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remove_from_page_cache(page);
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ClearPageUptodate(page);
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ClearPageMappedToDisk(page);
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page_cache_release(page); /* pagecache ref */
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}
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/*
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* This is for invalidate_mapping_pages(). That function can be called at
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* any time, and is not supposed to throw away dirty pages. But pages can
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* be marked dirty at any time too, so use remove_mapping which safely
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* discards clean, unused pages.
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*
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* Returns non-zero if the page was successfully invalidated.
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*/
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static int
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invalidate_complete_page(struct address_space *mapping, struct page *page)
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{
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int ret;
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if (page->mapping != mapping)
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return 0;
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if (PagePrivate(page) && !try_to_release_page(page, 0))
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return 0;
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ret = remove_mapping(mapping, page);
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return ret;
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}
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/**
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* truncate_inode_pages - truncate range of pages specified by start and
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* end byte offsets
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* @mapping: mapping to truncate
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* @lstart: offset from which to truncate
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* @lend: offset to which to truncate
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*
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* Truncate the page cache, removing the pages that are between
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* specified offsets (and zeroing out partial page
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* (if lstart is not page aligned)).
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*
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* Truncate takes two passes - the first pass is nonblocking. It will not
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* block on page locks and it will not block on writeback. The second pass
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* will wait. This is to prevent as much IO as possible in the affected region.
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* The first pass will remove most pages, so the search cost of the second pass
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* is low.
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*
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* When looking at page->index outside the page lock we need to be careful to
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* copy it into a local to avoid races (it could change at any time).
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*
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* We pass down the cache-hot hint to the page freeing code. Even if the
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* mapping is large, it is probably the case that the final pages are the most
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* recently touched, and freeing happens in ascending file offset order.
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*/
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void truncate_inode_pages_range(struct address_space *mapping,
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loff_t lstart, loff_t lend)
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{
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const pgoff_t start = (lstart + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
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pgoff_t end;
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const unsigned partial = lstart & (PAGE_CACHE_SIZE - 1);
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struct pagevec pvec;
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pgoff_t next;
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int i;
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if (mapping->nrpages == 0)
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return;
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BUG_ON((lend & (PAGE_CACHE_SIZE - 1)) != (PAGE_CACHE_SIZE - 1));
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end = (lend >> PAGE_CACHE_SHIFT);
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pagevec_init(&pvec, 0);
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next = start;
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while (next <= end &&
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pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
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for (i = 0; i < pagevec_count(&pvec); i++) {
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struct page *page = pvec.pages[i];
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pgoff_t page_index = page->index;
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if (page_index > end) {
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next = page_index;
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break;
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}
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if (page_index > next)
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next = page_index;
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next++;
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if (TestSetPageLocked(page))
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continue;
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if (PageWriteback(page)) {
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unlock_page(page);
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continue;
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}
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if (page_mapped(page)) {
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unmap_mapping_range(mapping,
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(loff_t)page_index<<PAGE_CACHE_SHIFT,
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PAGE_CACHE_SIZE, 0);
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}
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truncate_complete_page(mapping, page);
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unlock_page(page);
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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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if (partial) {
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struct page *page = find_lock_page(mapping, start - 1);
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if (page) {
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wait_on_page_writeback(page);
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truncate_partial_page(page, partial);
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unlock_page(page);
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page_cache_release(page);
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}
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}
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next = start;
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for ( ; ; ) {
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cond_resched();
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if (!pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
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if (next == start)
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break;
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next = start;
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continue;
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}
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if (pvec.pages[0]->index > end) {
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pagevec_release(&pvec);
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break;
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}
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for (i = 0; i < pagevec_count(&pvec); i++) {
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struct page *page = pvec.pages[i];
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if (page->index > end)
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break;
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lock_page(page);
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wait_on_page_writeback(page);
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if (page_mapped(page)) {
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unmap_mapping_range(mapping,
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(loff_t)page->index<<PAGE_CACHE_SHIFT,
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PAGE_CACHE_SIZE, 0);
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}
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if (page->index > next)
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next = page->index;
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next++;
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truncate_complete_page(mapping, page);
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unlock_page(page);
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}
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pagevec_release(&pvec);
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}
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}
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EXPORT_SYMBOL(truncate_inode_pages_range);
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/**
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* truncate_inode_pages - truncate *all* the pages from an offset
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* @mapping: mapping to truncate
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* @lstart: offset from which to truncate
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*
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* Called under (and serialised by) inode->i_mutex.
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*/
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void truncate_inode_pages(struct address_space *mapping, loff_t lstart)
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{
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truncate_inode_pages_range(mapping, lstart, (loff_t)-1);
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}
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EXPORT_SYMBOL(truncate_inode_pages);
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unsigned long __invalidate_mapping_pages(struct address_space *mapping,
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pgoff_t start, pgoff_t end, bool be_atomic)
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{
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struct pagevec pvec;
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pgoff_t next = start;
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unsigned long ret = 0;
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int i;
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pagevec_init(&pvec, 0);
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while (next <= end &&
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pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
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for (i = 0; i < pagevec_count(&pvec); i++) {
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struct page *page = pvec.pages[i];
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pgoff_t index;
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int lock_failed;
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lock_failed = TestSetPageLocked(page);
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/*
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* We really shouldn't be looking at the ->index of an
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* unlocked page. But we're not allowed to lock these
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* pages. So we rely upon nobody altering the ->index
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* of this (pinned-by-us) page.
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*/
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index = page->index;
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if (index > next)
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next = index;
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next++;
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if (lock_failed)
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continue;
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if (PageDirty(page) || PageWriteback(page))
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goto unlock;
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if (page_mapped(page))
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goto unlock;
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ret += invalidate_complete_page(mapping, page);
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unlock:
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unlock_page(page);
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if (next > end)
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break;
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}
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pagevec_release(&pvec);
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if (likely(!be_atomic))
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cond_resched();
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}
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return ret;
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}
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/**
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* invalidate_mapping_pages - Invalidate all the unlocked pages of one inode
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* @mapping: the address_space which holds the pages to invalidate
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* @start: the offset 'from' which to invalidate
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* @end: the offset 'to' which to invalidate (inclusive)
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*
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* This function only removes the unlocked pages, if you want to
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* remove all the pages of one inode, you must call truncate_inode_pages.
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*
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* invalidate_mapping_pages() will not block on IO activity. It will not
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* invalidate pages which are dirty, locked, under writeback or mapped into
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* pagetables.
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*/
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unsigned long invalidate_mapping_pages(struct address_space *mapping,
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pgoff_t start, pgoff_t end)
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{
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return __invalidate_mapping_pages(mapping, start, end, false);
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}
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EXPORT_SYMBOL(invalidate_mapping_pages);
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/*
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* This is like invalidate_complete_page(), except it ignores the page's
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* refcount. We do this because invalidate_inode_pages2() needs stronger
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* invalidation guarantees, and cannot afford to leave pages behind because
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* shrink_page_list() has a temp ref on them, or because they're transiently
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* sitting in the lru_cache_add() pagevecs.
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*/
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static int
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invalidate_complete_page2(struct address_space *mapping, struct page *page)
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{
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if (page->mapping != mapping)
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return 0;
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if (PagePrivate(page) && !try_to_release_page(page, GFP_KERNEL))
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return 0;
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write_lock_irq(&mapping->tree_lock);
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if (PageDirty(page))
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goto failed;
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BUG_ON(PagePrivate(page));
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__remove_from_page_cache(page);
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write_unlock_irq(&mapping->tree_lock);
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ClearPageUptodate(page);
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page_cache_release(page); /* pagecache ref */
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return 1;
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failed:
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write_unlock_irq(&mapping->tree_lock);
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return 0;
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}
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static int do_launder_page(struct address_space *mapping, struct page *page)
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{
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if (!PageDirty(page))
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return 0;
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if (page->mapping != mapping || mapping->a_ops->launder_page == NULL)
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return 0;
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return mapping->a_ops->launder_page(page);
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}
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/**
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* invalidate_inode_pages2_range - remove range of pages from an address_space
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* @mapping: the address_space
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* @start: the page offset 'from' which to invalidate
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* @end: the page offset 'to' which to invalidate (inclusive)
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*
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* Any pages which are found to be mapped into pagetables are unmapped prior to
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* invalidation.
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*
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* Returns -EIO if any pages could not be invalidated.
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*/
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int invalidate_inode_pages2_range(struct address_space *mapping,
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pgoff_t start, pgoff_t end)
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{
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struct pagevec pvec;
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pgoff_t next;
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int i;
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int ret = 0;
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int did_range_unmap = 0;
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int wrapped = 0;
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pagevec_init(&pvec, 0);
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next = start;
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while (next <= end && !wrapped &&
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pagevec_lookup(&pvec, mapping, next,
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min(end - next, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
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for (i = 0; i < pagevec_count(&pvec); i++) {
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struct page *page = pvec.pages[i];
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pgoff_t page_index;
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lock_page(page);
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if (page->mapping != mapping) {
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unlock_page(page);
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continue;
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}
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page_index = page->index;
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next = page_index + 1;
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if (next == 0)
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wrapped = 1;
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if (page_index > end) {
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unlock_page(page);
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break;
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}
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wait_on_page_writeback(page);
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if (page_mapped(page)) {
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if (!did_range_unmap) {
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/*
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* Zap the rest of the file in one hit.
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*/
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unmap_mapping_range(mapping,
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(loff_t)page_index<<PAGE_CACHE_SHIFT,
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(loff_t)(end - page_index + 1)
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<< PAGE_CACHE_SHIFT,
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0);
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did_range_unmap = 1;
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} else {
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/*
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* Just zap this page
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*/
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unmap_mapping_range(mapping,
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(loff_t)page_index<<PAGE_CACHE_SHIFT,
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PAGE_CACHE_SIZE, 0);
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}
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}
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BUG_ON(page_mapped(page));
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ret = do_launder_page(mapping, page);
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if (ret == 0 && !invalidate_complete_page2(mapping, page))
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ret = -EIO;
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unlock_page(page);
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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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return ret;
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}
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EXPORT_SYMBOL_GPL(invalidate_inode_pages2_range);
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/**
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* invalidate_inode_pages2 - remove all pages from an address_space
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* @mapping: the address_space
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*
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* Any pages which are found to be mapped into pagetables are unmapped prior to
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* invalidation.
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*
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* Returns -EIO if any pages could not be invalidated.
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*/
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int invalidate_inode_pages2(struct address_space *mapping)
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{
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return invalidate_inode_pages2_range(mapping, 0, -1);
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}
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EXPORT_SYMBOL_GPL(invalidate_inode_pages2);
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