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authorNick Piggin <npiggin@suse.de>2009-01-04 12:00:53 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2009-01-04 13:33:20 -0800
commit54566b2c1594c2326a645a3551f9d989f7ba3c5e (patch)
treeb373f3283fe5e197d0df29cd6b645c35adf1076c /fs/libfs.c
parente687d691cb3790d25e31c74f5941fd7c565e9df5 (diff)
downloadlwn-54566b2c1594c2326a645a3551f9d989f7ba3c5e.tar.gz
lwn-54566b2c1594c2326a645a3551f9d989f7ba3c5e.zip
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: Nick Piggin <npiggin@suse.de> Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: <stable@kernel.org> [2.6.28.x] Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: Andrew 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: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/libfs.c')
-rw-r--r--fs/libfs.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/libfs.c b/fs/libfs.c
index e960a8321902..bdaec17fa388 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -360,7 +360,7 @@ int simple_write_begin(struct file *file, struct address_space *mapping,
index = pos >> PAGE_CACHE_SHIFT;
from = pos & (PAGE_CACHE_SIZE - 1);
- page = __grab_cache_page(mapping, index);
+ page = grab_cache_page_write_begin(mapping, index, flags);
if (!page)
return -ENOMEM;