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[PATCH] page invalidation cleanup

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Clean up the invalidate code, and use a common function to safely remove
the page from pagecache.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Nick Piggin 2006-09-27 01:50:02 -07:00 committed by Linus Torvalds
parent 5b99cd0eff
commit 0fd0e6b05a
2 changed files with 31 additions and 21 deletions
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25
mm/truncate.c
View file

@ -9,6 +9,7 @@
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/module.h>
#include <linux/pagemap.h>
#include <linux/pagevec.h>
@ -52,36 +53,26 @@ truncate_complete_page(struct address_space *mapping, struct page *page)
/*
* This is for invalidate_inode_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 we re-check the dirtiness inside
* ->tree_lock. That provides exclusion against the __set_page_dirty
* functions.
* 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 (PagePrivate(page) && !try_to_release_page(page, 0))
return 0;
write_lock_irq(&mapping->tree_lock);
if (PageDirty(page))
goto failed;
if (page_count(page) != 2) /* caller's ref + pagecache ref */
goto failed;
BUG_ON(PagePrivate(page));
__remove_from_page_cache(page);
write_unlock_irq(&mapping->tree_lock);
ret = remove_mapping(mapping, page);
ClearPageUptodate(page);
page_cache_release(page); /* pagecache ref */
return 1;
failed:
write_unlock_irq(&mapping->tree_lock);
return 0;
return ret;
}
/**

27
mm/vmscan.c
View file

@ -384,11 +384,30 @@ int remove_mapping(struct address_space *mapping, struct page *page)
BUG_ON(mapping != page_mapping(page));
write_lock_irq(&mapping->tree_lock);
/*
* The non-racy check for busy page. It is critical to check
* PageDirty _after_ making sure that the page is freeable and
* not in use by anybody. (pagecache + us == 2)
* The non racy check for a busy page.
*
* Must be careful with the order of the tests. When someone has
* a ref to the page, it may be possible that they dirty it then
* drop the reference. So if PageDirty is tested before page_count
* here, then the following race may occur:
*
* get_user_pages(&page);
* [user mapping goes away]
* write_to(page);
* !PageDirty(page) [good]
* SetPageDirty(page);
* put_page(page);
* !page_count(page) [good, discard it]
*
* [oops, our write_to data is lost]
*
* Reversing the order of the tests ensures such a situation cannot
* escape unnoticed. The smp_rmb is needed to ensure the page->flags
* load is not satisfied before that of page->_count.
*
* Note that if SetPageDirty is always performed via set_page_dirty,
* and thus under tree_lock, then this ordering is not required.
*/
if (unlikely(page_count(page) != 2))
goto cannot_free;