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![Kirill A. Shutemov](/assets/img/avatar_default.png)
PAGE_CACHE_{SIZE,SHIFT,MASK,ALIGN} macros were introduced *long* time ago with promise that one day it will be possible to implement page cache with bigger chunks than PAGE_SIZE. This promise never materialized. And unlikely will. We have many places where PAGE_CACHE_SIZE assumed to be equal to PAGE_SIZE. And it's constant source of confusion on whether PAGE_CACHE_* or PAGE_* constant should be used in a particular case, especially on the border between fs and mm. Global switching to PAGE_CACHE_SIZE != PAGE_SIZE would cause to much breakage to be doable. Let's stop pretending that pages in page cache are special. They are not. The changes are pretty straight-forward: - <foo> << (PAGE_CACHE_SHIFT - PAGE_SHIFT) -> <foo>; - <foo> >> (PAGE_CACHE_SHIFT - PAGE_SHIFT) -> <foo>; - PAGE_CACHE_{SIZE,SHIFT,MASK,ALIGN} -> PAGE_{SIZE,SHIFT,MASK,ALIGN}; - page_cache_get() -> get_page(); - page_cache_release() -> put_page(); This patch contains automated changes generated with coccinelle using script below. For some reason, coccinelle doesn't patch header files. I've called spatch for them manually. The only adjustment after coccinelle is revert of changes to PAGE_CAHCE_ALIGN definition: we are going to drop it later. There are few places in the code where coccinelle didn't reach. I'll fix them manually in a separate patch. Comments and documentation also will be addressed with the separate patch. virtual patch @@ expression E; @@ - E << (PAGE_CACHE_SHIFT - PAGE_SHIFT) + E @@ expression E; @@ - E >> (PAGE_CACHE_SHIFT - PAGE_SHIFT) + E @@ @@ - PAGE_CACHE_SHIFT + PAGE_SHIFT @@ @@ - PAGE_CACHE_SIZE + PAGE_SIZE @@ @@ - PAGE_CACHE_MASK + PAGE_MASK @@ expression E; @@ - PAGE_CACHE_ALIGN(E) + PAGE_ALIGN(E) @@ expression E; @@ - page_cache_get(E) + get_page(E) @@ expression E; @@ - page_cache_release(E) + put_page(E) Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Acked-by: Michal Hocko <mhocko@suse.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
657 lines
15 KiB
C
657 lines
15 KiB
C
/*
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* Ram backed block device driver.
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*
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* Copyright (C) 2007 Nick Piggin
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* Copyright (C) 2007 Novell Inc.
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*
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* Parts derived from drivers/block/rd.c, and drivers/block/loop.c, copyright
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* of their respective owners.
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*/
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/moduleparam.h>
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#include <linux/major.h>
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#include <linux/blkdev.h>
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#include <linux/bio.h>
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#include <linux/highmem.h>
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#include <linux/mutex.h>
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#include <linux/radix-tree.h>
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#include <linux/fs.h>
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#include <linux/slab.h>
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#ifdef CONFIG_BLK_DEV_RAM_DAX
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#include <linux/pfn_t.h>
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#endif
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#include <asm/uaccess.h>
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#define SECTOR_SHIFT 9
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#define PAGE_SECTORS_SHIFT (PAGE_SHIFT - SECTOR_SHIFT)
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#define PAGE_SECTORS (1 << PAGE_SECTORS_SHIFT)
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/*
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* Each block ramdisk device has a radix_tree brd_pages of pages that stores
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* the pages containing the block device's contents. A brd page's ->index is
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* its offset in PAGE_SIZE units. This is similar to, but in no way connected
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* with, the kernel's pagecache or buffer cache (which sit above our block
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* device).
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*/
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struct brd_device {
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int brd_number;
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struct request_queue *brd_queue;
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struct gendisk *brd_disk;
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struct list_head brd_list;
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/*
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* Backing store of pages and lock to protect it. This is the contents
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* of the block device.
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*/
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spinlock_t brd_lock;
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struct radix_tree_root brd_pages;
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};
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/*
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* Look up and return a brd's page for a given sector.
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*/
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static DEFINE_MUTEX(brd_mutex);
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static struct page *brd_lookup_page(struct brd_device *brd, sector_t sector)
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{
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pgoff_t idx;
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struct page *page;
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/*
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* The page lifetime is protected by the fact that we have opened the
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* device node -- brd pages will never be deleted under us, so we
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* don't need any further locking or refcounting.
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*
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* This is strictly true for the radix-tree nodes as well (ie. we
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* don't actually need the rcu_read_lock()), however that is not a
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* documented feature of the radix-tree API so it is better to be
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* safe here (we don't have total exclusion from radix tree updates
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* here, only deletes).
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*/
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rcu_read_lock();
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idx = sector >> PAGE_SECTORS_SHIFT; /* sector to page index */
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page = radix_tree_lookup(&brd->brd_pages, idx);
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rcu_read_unlock();
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BUG_ON(page && page->index != idx);
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return page;
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}
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/*
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* Look up and return a brd's page for a given sector.
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* If one does not exist, allocate an empty page, and insert that. Then
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* return it.
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*/
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static struct page *brd_insert_page(struct brd_device *brd, sector_t sector)
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{
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pgoff_t idx;
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struct page *page;
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gfp_t gfp_flags;
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page = brd_lookup_page(brd, sector);
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if (page)
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return page;
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/*
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* Must use NOIO because we don't want to recurse back into the
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* block or filesystem layers from page reclaim.
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*
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* Cannot support DAX and highmem, because our ->direct_access
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* routine for DAX must return memory that is always addressable.
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* If DAX was reworked to use pfns and kmap throughout, this
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* restriction might be able to be lifted.
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*/
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gfp_flags = GFP_NOIO | __GFP_ZERO;
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#ifndef CONFIG_BLK_DEV_RAM_DAX
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gfp_flags |= __GFP_HIGHMEM;
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#endif
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page = alloc_page(gfp_flags);
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if (!page)
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return NULL;
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if (radix_tree_preload(GFP_NOIO)) {
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__free_page(page);
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return NULL;
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}
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spin_lock(&brd->brd_lock);
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idx = sector >> PAGE_SECTORS_SHIFT;
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page->index = idx;
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if (radix_tree_insert(&brd->brd_pages, idx, page)) {
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__free_page(page);
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page = radix_tree_lookup(&brd->brd_pages, idx);
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BUG_ON(!page);
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BUG_ON(page->index != idx);
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}
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spin_unlock(&brd->brd_lock);
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radix_tree_preload_end();
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return page;
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}
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static void brd_free_page(struct brd_device *brd, sector_t sector)
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{
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struct page *page;
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pgoff_t idx;
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spin_lock(&brd->brd_lock);
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idx = sector >> PAGE_SECTORS_SHIFT;
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page = radix_tree_delete(&brd->brd_pages, idx);
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spin_unlock(&brd->brd_lock);
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if (page)
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__free_page(page);
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}
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static void brd_zero_page(struct brd_device *brd, sector_t sector)
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{
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struct page *page;
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page = brd_lookup_page(brd, sector);
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if (page)
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clear_highpage(page);
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}
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/*
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* Free all backing store pages and radix tree. This must only be called when
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* there are no other users of the device.
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*/
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#define FREE_BATCH 16
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static void brd_free_pages(struct brd_device *brd)
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{
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unsigned long pos = 0;
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struct page *pages[FREE_BATCH];
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int nr_pages;
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do {
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int i;
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nr_pages = radix_tree_gang_lookup(&brd->brd_pages,
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(void **)pages, pos, FREE_BATCH);
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for (i = 0; i < nr_pages; i++) {
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void *ret;
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BUG_ON(pages[i]->index < pos);
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pos = pages[i]->index;
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ret = radix_tree_delete(&brd->brd_pages, pos);
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BUG_ON(!ret || ret != pages[i]);
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__free_page(pages[i]);
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}
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pos++;
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/*
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* This assumes radix_tree_gang_lookup always returns as
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* many pages as possible. If the radix-tree code changes,
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* so will this have to.
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*/
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} while (nr_pages == FREE_BATCH);
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}
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/*
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* copy_to_brd_setup must be called before copy_to_brd. It may sleep.
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*/
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static int copy_to_brd_setup(struct brd_device *brd, sector_t sector, size_t n)
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{
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unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT;
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size_t copy;
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copy = min_t(size_t, n, PAGE_SIZE - offset);
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if (!brd_insert_page(brd, sector))
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return -ENOSPC;
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if (copy < n) {
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sector += copy >> SECTOR_SHIFT;
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if (!brd_insert_page(brd, sector))
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return -ENOSPC;
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}
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return 0;
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}
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static void discard_from_brd(struct brd_device *brd,
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sector_t sector, size_t n)
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{
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while (n >= PAGE_SIZE) {
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/*
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* Don't want to actually discard pages here because
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* re-allocating the pages can result in writeback
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* deadlocks under heavy load.
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*/
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if (0)
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brd_free_page(brd, sector);
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else
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brd_zero_page(brd, sector);
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sector += PAGE_SIZE >> SECTOR_SHIFT;
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n -= PAGE_SIZE;
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}
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}
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/*
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* Copy n bytes from src to the brd starting at sector. Does not sleep.
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*/
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static void copy_to_brd(struct brd_device *brd, const void *src,
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sector_t sector, size_t n)
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{
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struct page *page;
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void *dst;
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unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT;
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size_t copy;
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copy = min_t(size_t, n, PAGE_SIZE - offset);
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page = brd_lookup_page(brd, sector);
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BUG_ON(!page);
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dst = kmap_atomic(page);
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memcpy(dst + offset, src, copy);
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kunmap_atomic(dst);
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if (copy < n) {
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src += copy;
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sector += copy >> SECTOR_SHIFT;
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copy = n - copy;
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page = brd_lookup_page(brd, sector);
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BUG_ON(!page);
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dst = kmap_atomic(page);
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memcpy(dst, src, copy);
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kunmap_atomic(dst);
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}
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}
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/*
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* Copy n bytes to dst from the brd starting at sector. Does not sleep.
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*/
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static void copy_from_brd(void *dst, struct brd_device *brd,
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sector_t sector, size_t n)
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{
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struct page *page;
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void *src;
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unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT;
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size_t copy;
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copy = min_t(size_t, n, PAGE_SIZE - offset);
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page = brd_lookup_page(brd, sector);
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if (page) {
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src = kmap_atomic(page);
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memcpy(dst, src + offset, copy);
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kunmap_atomic(src);
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} else
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memset(dst, 0, copy);
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if (copy < n) {
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dst += copy;
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sector += copy >> SECTOR_SHIFT;
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copy = n - copy;
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page = brd_lookup_page(brd, sector);
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if (page) {
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src = kmap_atomic(page);
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memcpy(dst, src, copy);
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kunmap_atomic(src);
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} else
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memset(dst, 0, copy);
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}
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}
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/*
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* Process a single bvec of a bio.
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*/
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static int brd_do_bvec(struct brd_device *brd, struct page *page,
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unsigned int len, unsigned int off, int rw,
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sector_t sector)
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{
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void *mem;
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int err = 0;
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if (rw != READ) {
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err = copy_to_brd_setup(brd, sector, len);
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if (err)
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goto out;
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}
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mem = kmap_atomic(page);
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if (rw == READ) {
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copy_from_brd(mem + off, brd, sector, len);
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flush_dcache_page(page);
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} else {
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flush_dcache_page(page);
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copy_to_brd(brd, mem + off, sector, len);
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}
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kunmap_atomic(mem);
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out:
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return err;
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}
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static blk_qc_t brd_make_request(struct request_queue *q, struct bio *bio)
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{
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struct block_device *bdev = bio->bi_bdev;
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struct brd_device *brd = bdev->bd_disk->private_data;
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int rw;
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struct bio_vec bvec;
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sector_t sector;
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struct bvec_iter iter;
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sector = bio->bi_iter.bi_sector;
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if (bio_end_sector(bio) > get_capacity(bdev->bd_disk))
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goto io_error;
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if (unlikely(bio->bi_rw & REQ_DISCARD)) {
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if (sector & ((PAGE_SIZE >> SECTOR_SHIFT) - 1) ||
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bio->bi_iter.bi_size & ~PAGE_MASK)
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goto io_error;
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discard_from_brd(brd, sector, bio->bi_iter.bi_size);
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goto out;
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}
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rw = bio_rw(bio);
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if (rw == READA)
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rw = READ;
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bio_for_each_segment(bvec, bio, iter) {
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unsigned int len = bvec.bv_len;
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int err;
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err = brd_do_bvec(brd, bvec.bv_page, len,
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bvec.bv_offset, rw, sector);
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if (err)
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goto io_error;
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sector += len >> SECTOR_SHIFT;
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}
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out:
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bio_endio(bio);
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return BLK_QC_T_NONE;
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io_error:
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bio_io_error(bio);
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return BLK_QC_T_NONE;
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}
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static int brd_rw_page(struct block_device *bdev, sector_t sector,
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struct page *page, int rw)
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{
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struct brd_device *brd = bdev->bd_disk->private_data;
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int err = brd_do_bvec(brd, page, PAGE_SIZE, 0, rw, sector);
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page_endio(page, rw & WRITE, err);
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return err;
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}
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#ifdef CONFIG_BLK_DEV_RAM_DAX
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static long brd_direct_access(struct block_device *bdev, sector_t sector,
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void __pmem **kaddr, pfn_t *pfn)
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{
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struct brd_device *brd = bdev->bd_disk->private_data;
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struct page *page;
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if (!brd)
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return -ENODEV;
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page = brd_insert_page(brd, sector);
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if (!page)
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return -ENOSPC;
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*kaddr = (void __pmem *)page_address(page);
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*pfn = page_to_pfn_t(page);
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return PAGE_SIZE;
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}
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#else
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#define brd_direct_access NULL
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#endif
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static int brd_ioctl(struct block_device *bdev, fmode_t mode,
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unsigned int cmd, unsigned long arg)
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{
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int error;
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struct brd_device *brd = bdev->bd_disk->private_data;
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if (cmd != BLKFLSBUF)
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return -ENOTTY;
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/*
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* ram device BLKFLSBUF has special semantics, we want to actually
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* release and destroy the ramdisk data.
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*/
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mutex_lock(&brd_mutex);
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mutex_lock(&bdev->bd_mutex);
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error = -EBUSY;
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if (bdev->bd_openers <= 1) {
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/*
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* Kill the cache first, so it isn't written back to the
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* device.
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*
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* Another thread might instantiate more buffercache here,
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* but there is not much we can do to close that race.
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*/
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kill_bdev(bdev);
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brd_free_pages(brd);
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error = 0;
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}
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mutex_unlock(&bdev->bd_mutex);
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mutex_unlock(&brd_mutex);
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return error;
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}
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static const struct block_device_operations brd_fops = {
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.owner = THIS_MODULE,
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.rw_page = brd_rw_page,
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.ioctl = brd_ioctl,
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.direct_access = brd_direct_access,
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};
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/*
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* And now the modules code and kernel interface.
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*/
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static int rd_nr = CONFIG_BLK_DEV_RAM_COUNT;
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module_param(rd_nr, int, S_IRUGO);
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MODULE_PARM_DESC(rd_nr, "Maximum number of brd devices");
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int rd_size = CONFIG_BLK_DEV_RAM_SIZE;
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module_param(rd_size, int, S_IRUGO);
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MODULE_PARM_DESC(rd_size, "Size of each RAM disk in kbytes.");
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static int max_part = 1;
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module_param(max_part, int, S_IRUGO);
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MODULE_PARM_DESC(max_part, "Num Minors to reserve between devices");
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MODULE_LICENSE("GPL");
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MODULE_ALIAS_BLOCKDEV_MAJOR(RAMDISK_MAJOR);
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MODULE_ALIAS("rd");
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#ifndef MODULE
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/* Legacy boot options - nonmodular */
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static int __init ramdisk_size(char *str)
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{
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rd_size = simple_strtol(str, NULL, 0);
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return 1;
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}
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__setup("ramdisk_size=", ramdisk_size);
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#endif
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/*
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* The device scheme is derived from loop.c. Keep them in synch where possible
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* (should share code eventually).
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*/
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static LIST_HEAD(brd_devices);
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static DEFINE_MUTEX(brd_devices_mutex);
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static struct brd_device *brd_alloc(int i)
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{
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struct brd_device *brd;
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struct gendisk *disk;
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brd = kzalloc(sizeof(*brd), GFP_KERNEL);
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if (!brd)
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goto out;
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brd->brd_number = i;
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spin_lock_init(&brd->brd_lock);
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INIT_RADIX_TREE(&brd->brd_pages, GFP_ATOMIC);
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|
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brd->brd_queue = blk_alloc_queue(GFP_KERNEL);
|
|
if (!brd->brd_queue)
|
|
goto out_free_dev;
|
|
|
|
blk_queue_make_request(brd->brd_queue, brd_make_request);
|
|
blk_queue_max_hw_sectors(brd->brd_queue, 1024);
|
|
blk_queue_bounce_limit(brd->brd_queue, BLK_BOUNCE_ANY);
|
|
|
|
/* This is so fdisk will align partitions on 4k, because of
|
|
* direct_access API needing 4k alignment, returning a PFN
|
|
* (This is only a problem on very small devices <= 4M,
|
|
* otherwise fdisk will align on 1M. Regardless this call
|
|
* is harmless)
|
|
*/
|
|
blk_queue_physical_block_size(brd->brd_queue, PAGE_SIZE);
|
|
|
|
brd->brd_queue->limits.discard_granularity = PAGE_SIZE;
|
|
blk_queue_max_discard_sectors(brd->brd_queue, UINT_MAX);
|
|
brd->brd_queue->limits.discard_zeroes_data = 1;
|
|
queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, brd->brd_queue);
|
|
|
|
disk = brd->brd_disk = alloc_disk(max_part);
|
|
if (!disk)
|
|
goto out_free_queue;
|
|
disk->major = RAMDISK_MAJOR;
|
|
disk->first_minor = i * max_part;
|
|
disk->fops = &brd_fops;
|
|
disk->private_data = brd;
|
|
disk->queue = brd->brd_queue;
|
|
disk->flags = GENHD_FL_EXT_DEVT;
|
|
sprintf(disk->disk_name, "ram%d", i);
|
|
set_capacity(disk, rd_size * 2);
|
|
|
|
return brd;
|
|
|
|
out_free_queue:
|
|
blk_cleanup_queue(brd->brd_queue);
|
|
out_free_dev:
|
|
kfree(brd);
|
|
out:
|
|
return NULL;
|
|
}
|
|
|
|
static void brd_free(struct brd_device *brd)
|
|
{
|
|
put_disk(brd->brd_disk);
|
|
blk_cleanup_queue(brd->brd_queue);
|
|
brd_free_pages(brd);
|
|
kfree(brd);
|
|
}
|
|
|
|
static struct brd_device *brd_init_one(int i, bool *new)
|
|
{
|
|
struct brd_device *brd;
|
|
|
|
*new = false;
|
|
list_for_each_entry(brd, &brd_devices, brd_list) {
|
|
if (brd->brd_number == i)
|
|
goto out;
|
|
}
|
|
|
|
brd = brd_alloc(i);
|
|
if (brd) {
|
|
add_disk(brd->brd_disk);
|
|
list_add_tail(&brd->brd_list, &brd_devices);
|
|
}
|
|
*new = true;
|
|
out:
|
|
return brd;
|
|
}
|
|
|
|
static void brd_del_one(struct brd_device *brd)
|
|
{
|
|
list_del(&brd->brd_list);
|
|
del_gendisk(brd->brd_disk);
|
|
brd_free(brd);
|
|
}
|
|
|
|
static struct kobject *brd_probe(dev_t dev, int *part, void *data)
|
|
{
|
|
struct brd_device *brd;
|
|
struct kobject *kobj;
|
|
bool new;
|
|
|
|
mutex_lock(&brd_devices_mutex);
|
|
brd = brd_init_one(MINOR(dev) / max_part, &new);
|
|
kobj = brd ? get_disk(brd->brd_disk) : NULL;
|
|
mutex_unlock(&brd_devices_mutex);
|
|
|
|
if (new)
|
|
*part = 0;
|
|
|
|
return kobj;
|
|
}
|
|
|
|
static int __init brd_init(void)
|
|
{
|
|
struct brd_device *brd, *next;
|
|
int i;
|
|
|
|
/*
|
|
* brd module now has a feature to instantiate underlying device
|
|
* structure on-demand, provided that there is an access dev node.
|
|
*
|
|
* (1) if rd_nr is specified, create that many upfront. else
|
|
* it defaults to CONFIG_BLK_DEV_RAM_COUNT
|
|
* (2) User can further extend brd devices by create dev node themselves
|
|
* and have kernel automatically instantiate actual device
|
|
* on-demand. Example:
|
|
* mknod /path/devnod_name b 1 X # 1 is the rd major
|
|
* fdisk -l /path/devnod_name
|
|
* If (X / max_part) was not already created it will be created
|
|
* dynamically.
|
|
*/
|
|
|
|
if (register_blkdev(RAMDISK_MAJOR, "ramdisk"))
|
|
return -EIO;
|
|
|
|
if (unlikely(!max_part))
|
|
max_part = 1;
|
|
|
|
for (i = 0; i < rd_nr; i++) {
|
|
brd = brd_alloc(i);
|
|
if (!brd)
|
|
goto out_free;
|
|
list_add_tail(&brd->brd_list, &brd_devices);
|
|
}
|
|
|
|
/* point of no return */
|
|
|
|
list_for_each_entry(brd, &brd_devices, brd_list)
|
|
add_disk(brd->brd_disk);
|
|
|
|
blk_register_region(MKDEV(RAMDISK_MAJOR, 0), 1UL << MINORBITS,
|
|
THIS_MODULE, brd_probe, NULL, NULL);
|
|
|
|
pr_info("brd: module loaded\n");
|
|
return 0;
|
|
|
|
out_free:
|
|
list_for_each_entry_safe(brd, next, &brd_devices, brd_list) {
|
|
list_del(&brd->brd_list);
|
|
brd_free(brd);
|
|
}
|
|
unregister_blkdev(RAMDISK_MAJOR, "ramdisk");
|
|
|
|
pr_info("brd: module NOT loaded !!!\n");
|
|
return -ENOMEM;
|
|
}
|
|
|
|
static void __exit brd_exit(void)
|
|
{
|
|
struct brd_device *brd, *next;
|
|
|
|
list_for_each_entry_safe(brd, next, &brd_devices, brd_list)
|
|
brd_del_one(brd);
|
|
|
|
blk_unregister_region(MKDEV(RAMDISK_MAJOR, 0), 1UL << MINORBITS);
|
|
unregister_blkdev(RAMDISK_MAJOR, "ramdisk");
|
|
|
|
pr_info("brd: module unloaded\n");
|
|
}
|
|
|
|
module_init(brd_init);
|
|
module_exit(brd_exit);
|
|
|