Commit 0fd0e6b0 authored by Nicholas Piggin's avatar Nicholas Piggin Committed by Linus Torvalds
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[PATCH] page invalidation cleanup 



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

Signed-off-by: default avatarNick Piggin <npiggin@suse.de>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 5b99cd0e

mm/truncate.c

+8 −17
Original line number Diff line number Diff line
@@ -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;

}



/**

mm/vmscan.c

+23 −4
Original line number Diff line number Diff line
@@ -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;