Commit 6072d13c authored by Linus Torvalds's avatar Linus Torvalds Committed by Trond Myklebust
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Call the filesystem back whenever a page is removed from the page cache 



NFS needs to be able to release objects that are stored in the page
cache once the page itself is no longer visible from the page cache.

This patch adds a callback to the address space operations that allows
filesystems to perform page cleanups once the page has been removed
from the page cache.

Original patch by: Linus Torvalds <torvalds@linux-foundation.org>
[trondmy: cover the cases of invalidate_inode_pages2() and
          truncate_inode_pages()]
Signed-off-by: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
parent 0aded708

Documentation/filesystems/Locking

+6 −1
Original line number Diff line number Diff line
@@ -173,12 +173,13 @@ prototypes: 
	sector_t (*bmap)(struct address_space *, sector_t);

	int (*invalidatepage) (struct page *, unsigned long);

	int (*releasepage) (struct page *, int);

	void (*freepage)(struct page *);

	int (*direct_IO)(int, struct kiocb *, const struct iovec *iov,

			loff_t offset, unsigned long nr_segs);

	int (*launder_page) (struct page *);



locking rules:

	All except set_page_dirty may block

	All except set_page_dirty and freepage may block



			BKL	PageLocked(page)	i_mutex

writepage:		no	yes, unlocks (see below)
@@ -193,6 +194,7 @@ perform_write: no n/a yes 
bmap:			no

invalidatepage:		no	yes

releasepage:		no	yes

freepage:		no	yes

direct_IO:		no

launder_page:		no	yes
@@ -288,6 +290,9 @@ buffers from the page in preparation for freeing it. It returns zero to 
indicate that the buffers are (or may be) freeable.  If ->releasepage is zero,

the kernel assumes that the fs has no private interest in the buffers.



	->freepage() is called when the kernel is done dropping the page

from the page cache.



	->launder_page() may be called prior to releasing a page if

it is still found to be dirty. It returns zero if the page was successfully

cleaned, or an error value if not. Note that in order to prevent the page

Documentation/filesystems/vfs.txt

+7 −0
Original line number Diff line number Diff line
@@ -534,6 +534,7 @@ struct address_space_operations { 
	sector_t (*bmap)(struct address_space *, sector_t);

	int (*invalidatepage) (struct page *, unsigned long);

	int (*releasepage) (struct page *, int);

	void (*freepage)(struct page *);

	ssize_t (*direct_IO)(int, struct kiocb *, const struct iovec *iov,

			loff_t offset, unsigned long nr_segs);

	struct page* (*get_xip_page)(struct address_space *, sector_t,
@@ -679,6 +680,12 @@ struct address_space_operations { 
        need to ensure this.  Possibly it can clear the PageUptodate

        bit if it cannot free private data yet.



  freepage: freepage is called once the page is no longer visible in

        the page cache in order to allow the cleanup of any private

	data. Since it may be called by the memory reclaimer, it

	should not assume that the original address_space mapping still

	exists, and it should not block.



  direct_IO: called by the generic read/write routines to perform

        direct_IO - that is IO requests which bypass the page cache

        and transfer data directly between the storage and the

include/linux/fs.h

+1 −0
Original line number Diff line number Diff line
@@ -602,6 +602,7 @@ struct address_space_operations { 
	sector_t (*bmap)(struct address_space *, sector_t);

	void (*invalidatepage) (struct page *, unsigned long);

	int (*releasepage) (struct page *, gfp_t);

	void (*freepage)(struct page *);

	ssize_t (*direct_IO)(int, struct kiocb *, const struct iovec *iov,

			loff_t offset, unsigned long nr_segs);

	int (*get_xip_mem)(struct address_space *, pgoff_t, int,

mm/filemap.c

+5 −0
Original line number Diff line number Diff line
@@ -143,13 +143,18 @@ void __remove_from_page_cache(struct page *page) 
void remove_from_page_cache(struct page *page)

{

	struct address_space *mapping = page->mapping;

	void (*freepage)(struct page *);



	BUG_ON(!PageLocked(page));



	freepage = mapping->a_ops->freepage;

	spin_lock_irq(&mapping->tree_lock);

	__remove_from_page_cache(page);

	spin_unlock_irq(&mapping->tree_lock);

	mem_cgroup_uncharge_cache_page(page);



	if (freepage)

		freepage(page);

}

EXPORT_SYMBOL(remove_from_page_cache);

mm/truncate.c

+4 −0
Original line number Diff line number Diff line
@@ -390,6 +390,10 @@ invalidate_complete_page2(struct address_space *mapping, struct page *page) 
	__remove_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:

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