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Commit 54566b2c authored by Nick Piggin's avatar Nick Piggin Committed by Linus Torvalds
Browse files

fs: symlink write_begin allocation context fix 



With the write_begin/write_end aops, page_symlink was broken because it
could no longer pass a GFP_NOFS type mask into the point where the
allocations happened.  They are done in write_begin, which would always
assume that the filesystem can be entered from reclaim.  This bug could
cause filesystem deadlocks.

The funny thing with having a gfp_t mask there is that it doesn't really
allow the caller to arbitrarily tinker with the context in which it can be
called.  It couldn't ever be GFP_ATOMIC, for example, because it needs to
take the page lock.  The only thing any callers care about is __GFP_FS
anyway, so turn that into a single flag.

Add a new flag for write_begin, AOP_FLAG_NOFS.  Filesystems can now act on
this flag in their write_begin function.  Change __grab_cache_page to
accept a nofs argument as well, to honour that flag (while we're there,
change the name to grab_cache_page_write_begin which is more instructive
and does away with random leading underscores).

This is really a more flexible way to go in the end anyway -- if a
filesystem happens to want any extra allocations aside from the pagecache
ones in ints write_begin function, it may now use GFP_KERNEL (rather than
GFP_NOFS) for common case allocations (eg.  ocfs2_alloc_write_ctxt, for a
random example).

[kosaki.motohiro@jp.fujitsu.com: fix ubifs]
[kosaki.motohiro@jp.fujitsu.com: fix fuse]
Signed-off-by: default avatarNick Piggin <npiggin@suse.de>
Reviewed-by: default avatarKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: <stable@kernel.org>		[2.6.28.x]
Signed-off-by: default avatarKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
[ Cleaned up the calling convention: just pass in the AOP flags
  untouched to the grab_cache_page_write_begin() function.  That
  just simplifies everybody, and may even allow future expansion of the
  logic.   - Linus ]
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent e687d691

fs/affs/file.c

+1 −1
Original line number Diff line number Diff line
@@ -628,7 +628,7 @@ static int affs_write_begin_ofs(struct file *file, struct address_space *mapping 
	}



	index = pos >> PAGE_CACHE_SHIFT;

	page = __grab_cache_page(mapping, index);

	page = grab_cache_page_write_begin(mapping, index, flags);

	if (!page)

		return -ENOMEM;

	*pagep = page;

fs/afs/write.c

+1 −1
Original line number Diff line number Diff line
@@ -144,7 +144,7 @@ int afs_write_begin(struct file *file, struct address_space *mapping, 
	candidate->state = AFS_WBACK_PENDING;

	init_waitqueue_head(&candidate->waitq);



	page = __grab_cache_page(mapping, index);

	page = grab_cache_page_write_begin(mapping, index, flags);

	if (!page) {

		kfree(candidate);

		return -ENOMEM;

fs/buffer.c

+2 −2
Original line number Diff line number Diff line
@@ -1996,7 +1996,7 @@ int block_write_begin(struct file *file, struct address_space *mapping, 
	page = *pagep;

	if (page == NULL) {

		ownpage = 1;

		page = __grab_cache_page(mapping, index);

		page = grab_cache_page_write_begin(mapping, index, flags);

		if (!page) {

			status = -ENOMEM;

			goto out;
@@ -2502,7 +2502,7 @@ int nobh_write_begin(struct file *file, struct address_space *mapping, 
	from = pos & (PAGE_CACHE_SIZE - 1);

	to = from + len;



	page = __grab_cache_page(mapping, index);

	page = grab_cache_page_write_begin(mapping, index, flags);

	if (!page)

		return -ENOMEM;

	*pagep = page;

fs/cifs/file.c

+1 −1
Original line number Diff line number Diff line
@@ -2074,7 +2074,7 @@ static int cifs_write_begin(struct file *file, struct address_space *mapping, 


	cFYI(1, ("write_begin from %lld len %d", (long long)pos, len));



	page = __grab_cache_page(mapping, index);

	page = grab_cache_page_write_begin(mapping, index, flags);

	if (!page) {

		rc = -ENOMEM;

		goto out;

fs/ecryptfs/mmap.c

+1 −1
Original line number Diff line number Diff line
@@ -288,7 +288,7 @@ static int ecryptfs_write_begin(struct file *file, 
	loff_t prev_page_end_size;

	int rc = 0;



	page = __grab_cache_page(mapping, index);

	page = grab_cache_page_write_begin(mapping, index, flags);

	if (!page)

		return -ENOMEM;

	*pagep = page;