- 根目录:
- mm
- truncate.c
/*
* mm/truncate.c - code for taking down pages from address_spaces
*
* Copyright (C) 2002, Linus Torvalds
*
* 10Sep2002 Andrew Morton
* Initial version.
*/
#include <linux/kernel.h>
#include <linux/backing-dev.h>
#include <linux/gfp.h>
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/module.h>
#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/pagevec.h>
#include <linux/task_io_accounting_ops.h>
#include <linux/buffer_head.h> /* grr. try_to_release_page,
do_invalidatepage */
#include "internal.h"
/**
* do_invalidatepage - invalidate part or all of a page
* @page: the page which is affected
* @offset: the index of the truncation point
*
* do_invalidatepage() is called when all or part of the page has become
* invalidated by a truncate operation.
*
* do_invalidatepage() does not have to release all buffers, but it must
* ensure that no dirty buffer is left outside @offset and that no I/O
* is underway against any of the blocks which are outside the truncation
* point. Because the caller is about to free (and possibly reuse) those
* blocks on-disk.
*/
void do_invalidatepage(struct page *page, unsigned long offset)
{
void (*invalidatepage)(struct page *, unsigned long);
invalidatepage = page->mapping->a_ops->invalidatepage;
#ifdef CONFIG_BLOCK
if (!invalidatepage)
invalidatepage = block_invalidatepage;
#endif
if (invalidatepage)
(*invalidatepage)(page, offset);
}
static inline void truncate_partial_page(struct page *page, unsigned partial)
{
zero_user_segment(page, partial, PAGE_CACHE_SIZE);
if (page_has_private(page))
do_invalidatepage(page, partial);
}
/*
* This cancels just the dirty bit on the kernel page itself, it
* does NOT actually remove dirty bits on any mmap's that may be
* around. It also leaves the page tagged dirty, so any sync
* activity will still find it on the dirty lists, and in particular,
* clear_page_dirty_for_io() will still look at the dirty bits in
* the VM.
*
* Doing this should *normally* only ever be done when a page
* is truncated, and is not actually mapped anywhere at all. However,
* fs/buffer.c does this when it notices that somebody has cleaned
* out all the buffers on a page without actually doing it through
* the VM. Can you say "ext3 is horribly ugly"? Tought you could.
*/
void cancel_dirty_page(struct page *page, unsigned int account_size)
{
if (TestClearPageDirty(page)) {
struct address_space *mapping = page->mapping;
if (mapping && mapping_cap_account_dirty(mapping)) {
dec_zone_page_state(page, NR_FILE_DIRTY);
dec_bdi_stat(mapping->backing_dev_info,
BDI_RECLAIMABLE);
if (account_size)
task_io_account_cancelled_write(account_size);
}
}
}
EXPORT_SYMBOL(cancel_dirty_page);
/*
* If truncate cannot remove the fs-private metadata from the page, the page
* becomes orphaned. It will be left on the LRU and may even be mapped into
* user pagetables if we're racing with filemap_fault().
*
* We need to bale out if page->mapping is no longer equal to the original
* mapping. This happens a) when the VM reclaimed the page while we waited on
* its lock, b) when a concurrent invalidate_mapping_pages got there first and
* c) when tmpfs swizzles a page between a tmpfs inode and swapper_space.
*/
static int
truncate_complete_page(struct address_space *mapping, struct page *page)
{
if (page->mapping != mapping)
return -EIO;
if (page_has_private(page))
do_invalidatepage(page, 0);
cancel_dirty_page(page, PAGE_CACHE_SIZE);
clear_page_mlock(page);
ClearPageMappedToDisk(page);
delete_from_page_cache(page);
return 0;
}
/*
* This is for invalidate_mapping_pages(). That function can be called at
* any time, and is not supposed to throw away dirty pages. But pages can
* be marked dirty at any time too, so use remove_mapping which safely
* discards clean, unused pages.
*
* Returns non-zero if the page was successfully invalidated.
*/
static int
invalidate_complete_page(struct address_space *mapping, struct page *page)
{
int ret;
if (page->mapping != mapping)
return 0;
if (page_has_private(page) && !try_to_release_page(page, 0))
return 0;
clear_page_mlock(page);
ret = remove_mapping(mapping, page);
return ret;
}
int truncate_inode_page(struct address_space *mapping, struct page *page)
{
if (page_mapped(page)) {
unmap_mapping_range(mapping,
(loff_t)page->index << PAGE_CACHE_SHIFT,
PAGE_CACHE_SIZE, 0);
}
return truncate_complete_page(mapping, page);
}
/*
* Used to get rid of pages on hardware memory corruption.
*/
int generic_error_remove_page(struct address_space *mapping, struct page *page)
{
if (!mapping)
return -EINVAL;
/*
* Only punch for normal data pages for now.
* Handling other types like directories would need more auditing.
*/
if (!S_ISREG(mapping->host->i_mode))
return -EIO;
return truncate_inode_page(mapping, page);
}
EXPORT_SYMBOL(generic_error_remove_page);
/*
* Safely invalidate one page from its pagecache mapping.
* It only drops clean, unused pages. The page must be locked.
*
* Returns 1 if the page is successfully invalidated, otherwise 0.
*/
int invalidate_inode_page(struct page *page)
{
struct address_space *mapping = page_mapping(page);
if (!mapping)
return 0;
if (PageDirty(page) || PageWriteback(page))
return 0;
if (page_mapped(page))
return 0;
return invalidate_complete_page(mapping, page);
}
/**
* truncate_inode_pages - truncate range of pages specified by start & end byte offsets
* @mapping: mapping to truncate
* @lstart: offset from which to truncate
* @lend: offset to which to truncate
*
* Truncate the page cache, removing the pages that are between
* specified offsets (and zeroing out partial page
* (if lstart is not page aligned)).
*
* Truncate takes two passes - the first pass is nonblocking. It will not
* block on page locks and it will not block on writeback. The second pass
* will wait. This is to prevent as much IO as possible in the affected region.
* The first pass will remove most pages, so the search cost of the second pass
* is low.
*
* When looking at page->index outside the page lock we need to be careful to
* copy it into a local to avoid races (it could change at any time).
*
* We pass down the cache-hot hint to the page freeing code. Even if the
* mapping is large, it is probably the case that the final pages are the most
* recently touched, and freeing happens in ascending file offset order.
*/
void truncate_inode_pages_range(struct address_space *mapping,
loff_t lstart, loff_t lend)
{
const pgoff_t start = (lstart + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
pgoff_t end;
const unsigned partial = lstart & (PAGE_CACHE_SIZE - 1);
struct pagevec pvec;
pgoff_t next;
int i;
if (mapping->nrpages == 0)
return;
BUG_ON((lend & (PAGE_CACHE_SIZE - 1)) != (PAGE_CACHE_SIZE - 1));
end = (lend >> PAGE_CACHE_SHIFT);
pagevec_init(&pvec, 0);
next = start;
while (next <= end &&
pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
mem_cgroup_uncharge_start();
for (i = 0; i < pagevec_count(&pvec); i++) {
struct page *page = pvec.pages[i];
pgoff_t page_index = page->index;
if (page_index > end) {
next = page_index;
break;
}
if (page_index > next)
next = page_index;
next++;
if (!trylock_page(page))
continue;
if (PageWriteback(page)) {
unlock_page(page);
continue;
}
truncate_inode_page(mapping, page);
unlock_page(page);
}
pagevec_release(&pvec);
mem_cgroup_uncharge_end();
cond_resched();
}
if (partial) {
struct page *page = find_lock_page(mapping, start - 1);
if (page) {
wait_on_page_writeback(page);
truncate_partial_page(page, partial);
unlock_page(page);
page_cache_release(page);
}
}
next = start;
for ( ; ; ) {
cond_resched();
if (!pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
if (next == start)
break;
next = start;
continue;
}
if (pvec.pages[0]->index > end) {
pagevec_release(&pvec);
break;
}
mem_cgroup_uncharge_start();
for (i = 0; i < pagevec_count(&pvec); i++) {
struct page *page = pvec.pages[i];
if (page->index > end)
break;
lock_page(page);
wait_on_page_writeback(page);
truncate_inode_page(mapping, page);
if (page->index > next)
next = page->index;
next++;
unlock_page(page);
}
pagevec_release(&pvec);
mem_cgroup_uncharge_end();
}
}
EXPORT_SYMBOL(truncate_inode_pages_range);
/**
* truncate_inode_pages - truncate *all* the pages from an offset
* @mapping: mapping to truncate
* @lstart: offset from which to truncate
*
* Called under (and serialised by) inode->i_mutex.
*/
void truncate_inode_pages(struct address_space *mapping, loff_t lstart)
{
truncate_inode_pages_range(mapping, lstart, (loff_t)-1);
}
EXPORT_SYMBOL(truncate_inode_pages);
/**
* invalidate_mapping_pages - Invalidate all the unlocked pages of one inode
* @mapping: the address_space which holds the pages to invalidate
* @start: the offset 'from' which to invalidate
* @end: the offset 'to' which to invalidate (inclusive)
*
* This function only removes the unlocked pages, if you want to
* remove all the pages of one inode, you must call truncate_inode_pages.
*
* invalidate_mapping_pages() will not block on IO activity. It will not
* invalidate pages which are dirty, locked, under writeback or mapped into
* pagetables.
*/
unsigned long invalidate_mapping_pages(struct address_space *mapping,
pgoff_t start, pgoff_t end)
{
struct pagevec pvec;
pgoff_t next = start;
unsigned long ret;
unsigned long count = 0;
int i;
pagevec_init(&pvec, 0);
while (next <= end &&
pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
mem_cgroup_uncharge_start();
for (i = 0; i < pagevec_count(&pvec); i++) {
struct page *page = pvec.pages[i];
pgoff_t index;
int lock_failed;
lock_failed = !trylock_page(page);
/*
* We really shouldn't be looking at the ->index of an
* unlocked page. But we're not allowed to lock these
* pages. So we rely upon nobody altering the ->index
* of this (pinned-by-us) page.
*/
index = page->index;
if (index > next)
next = index;
next++;
if (lock_failed)
continue;
ret = invalidate_inode_page(page);
unlock_page(page);
/*
* Invalidation is a hint that the page is no longer
* of interest and try to speed up its reclaim.
*/
if (!ret)
deactivate_page(page);
count += ret;
if (next > end)
break;
}
pagevec_release(&pvec);
mem_cgroup_uncharge_end();
cond_resched();
}
return count;
}
EXPORT_SYMBOL(invalidate_mapping_pages);
/*
* This is like invalidate_complete_page(), except it ignores the page's
* refcount. We do this because invalidate_inode_pages2() needs stronger
* invalidation guarantees, and cannot afford to leave pages behind because
* shrink_page_list() has a temp ref on them, or because they're transiently
* sitting in the lru_cache_add() pagevecs.
*/
static int
invalidate_complete_page2(struct address_space *mapping, struct page *page)
{
if (page->mapping != mapping)
return 0;
if (page_has_private(page) && !try_to_release_page(page, GFP_KERNEL))
return 0;
spin_lock_irq(&mapping->tree_lock);
if (PageDirty(page))
goto failed;
clear_page_mlock(page);
BUG_ON(page_has_private(page));
__delete_from_page_cache(page);
spin_unlock_irq(&mapping->tree_lock);
mem_cgroup_uncharge_cache_page(page);
if (mapping->a_ops->freepage)
mapping->a_ops->freepage(page);
page_cache_release(page); /* pagecache ref */
return 1;
failed:
spin_unlock_irq(&mapping->tree_lock);
return 0;
}
static int do_launder_page(struct address_space *mapping, struct page *page)
{
if (!PageDirty(page))
return 0;
if (page->mapping != mapping || mapping->a_ops->launder_page == NULL)
return 0;
return mapping->a_ops->launder_page(page);
}
/**
* invalidate_inode_pages2_range - remove range of pages from an address_space
* @mapping: the address_space
* @start: the page offset 'from' which to invalidate
* @end: the page offset 'to' which to invalidate (inclusive)
*
* Any pages which are found to be mapped into pagetables are unmapped prior to
* invalidation.
*
* Returns -EBUSY if any pages could not be invalidated.
*/
int invalidate_inode_pages2_range(struct address_space *mapping,
pgoff_t start, pgoff_t end)
{
struct pagevec pvec;
pgoff_t next;
int i;
int ret = 0;
int ret2 = 0;
int did_range_unmap = 0;
int wrapped = 0;
pagevec_init(&pvec, 0);
next = start;
while (next <= end && !wrapped &&
pagevec_lookup(&pvec, mapping, next,
min(end - next, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
mem_cgroup_uncharge_start();
for (i = 0; i < pagevec_count(&pvec); i++) {
struct page *page = pvec.pages[i];
pgoff_t page_index;
lock_page(page);
if (page->mapping != mapping) {
unlock_page(page);
continue;
}
page_index = page->index;
next = page_index + 1;
if (next == 0)
wrapped = 1;
if (page_index > end) {
unlock_page(page);
break;
}
wait_on_page_writeback(page);
if (page_mapped(page)) {
if (!did_range_unmap) {
/*
* Zap the rest of the file in one hit.
*/
unmap_mapping_range(mapping,
(loff_t)page_index<<PAGE_CACHE_SHIFT,
(loff_t)(end - page_index + 1)
<< PAGE_CACHE_SHIFT,
0);
did_range_unmap = 1;
} else {
/*
* Just zap this page
*/
unmap_mapping_range(mapping,
(loff_t)page_index<<PAGE_CACHE_SHIFT,
PAGE_CACHE_SIZE, 0);
}
}
BUG_ON(page_mapped(page));
ret2 = do_launder_page(mapping, page);
if (ret2 == 0) {
if (!invalidate_complete_page2(mapping, page))
ret2 = -EBUSY;
}
if (ret2 < 0)
ret = ret2;
unlock_page(page);
}
pagevec_release(&pvec);
mem_cgroup_uncharge_end();
cond_resched();
}
return ret;
}
EXPORT_SYMBOL_GPL(invalidate_inode_pages2_range);
/**
* invalidate_inode_pages2 - remove all pages from an address_space
* @mapping: the address_space
*
* Any pages which are found to be mapped into pagetables are unmapped prior to
* invalidation.
*
* Returns -EBUSY if any pages could not be invalidated.
*/
int invalidate_inode_pages2(struct address_space *mapping)
{
return invalidate_inode_pages2_range(mapping, 0, -1);
}
EXPORT_SYMBOL_GPL(invalidate_inode_pages2);
/**
* truncate_pagecache - unmap and remove pagecache that has been truncated
* @inode: inode
* @old: old file offset
* @new: new file offset
*
* inode's new i_size must already be written before truncate_pagecache
* is called.
*
* This function should typically be called before the filesystem
* releases resources associated with the freed range (eg. deallocates
* blocks). This way, pagecache will always stay logically coherent
* with on-disk format, and the filesystem would not have to deal with
* situations such as writepage being called for a page that has already
* had its underlying blocks deallocated.
*/
void truncate_pagecache(struct inode *inode, loff_t old, loff_t new)
{
struct address_space *mapping = inode->i_mapping;
/*
* unmap_mapping_range is called twice, first simply for
* efficiency so that truncate_inode_pages does fewer
* single-page unmaps. However after this first call, and
* before truncate_inode_pages finishes, it is possible for
* private pages to be COWed, which remain after
* truncate_inode_pages finishes, hence the second
* unmap_mapping_range call must be made for correctness.
*/
unmap_mapping_range(mapping, new + PAGE_SIZE - 1, 0, 1);
truncate_inode_pages(mapping, new);
unmap_mapping_range(mapping, new + PAGE_SIZE - 1, 0, 1);
}
EXPORT_SYMBOL(truncate_pagecache);
/**
* truncate_setsize - update inode and pagecache for a new file size
* @inode: inode
* @newsize: new file size
*
* truncate_setsize updates i_size and performs pagecache truncation (if
* necessary) to @newsize. It will be typically be called from the filesystem's
* setattr function when ATTR_SIZE is passed in.
*
* Must be called with inode_mutex held and before all filesystem specific
* block truncation has been performed.
*/
void truncate_setsize(struct inode *inode, loff_t newsize)
{
loff_t oldsize;
oldsize = inode->i_size;
i_size_write(inode, newsize);
truncate_pagecache(inode, oldsize, newsize);
}
EXPORT_SYMBOL(truncate_setsize);
/**
* vmtruncate - unmap mappings "freed" by truncate() syscall
* @inode: inode of the file used
* @offset: file offset to start truncating
*
* This function is deprecated and truncate_setsize or truncate_pagecache
* should be used instead, together with filesystem specific block truncation.
*/
int vmtruncate(struct inode *inode, loff_t offset)
{
int error;
error = inode_newsize_ok(inode, offset);
if (error)
return error;
truncate_setsize(inode, offset);
if (inode->i_op->truncate)
inode->i_op->truncate(inode);
return 0;
}
EXPORT_SYMBOL(vmtruncate);