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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 /mm/filemap.c
parente687d691cb3790d25e31c74f5941fd7c565e9df5 (diff)
downloadconfigs-54566b2c1594c2326a645a3551f9d989f7ba3c5e.tar.gz
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 'mm/filemap.c')
-rw-r--r--mm/filemap.c13
1 files changed, 9 insertions, 4 deletions
diff --git a/mm/filemap.c b/mm/filemap.c
index f3e5f8944d1..f8c69273c37 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2140,19 +2140,24 @@ EXPORT_SYMBOL(generic_file_direct_write);
* Find or create a page at the given pagecache position. Return the locked
* page. This function is specifically for buffered writes.
*/
-struct page *__grab_cache_page(struct address_space *mapping, pgoff_t index)
+struct page *grab_cache_page_write_begin(struct address_space *mapping,
+ pgoff_t index, unsigned flags)
{
int status;
struct page *page;
+ gfp_t gfp_notmask = 0;
+ if (flags & AOP_FLAG_NOFS)
+ gfp_notmask = __GFP_FS;
repeat:
page = find_lock_page(mapping, index);
if (likely(page))
return page;
- page = page_cache_alloc(mapping);
+ page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~gfp_notmask);
if (!page)
return NULL;
- status = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL);
+ status = add_to_page_cache_lru(page, mapping, index,
+ GFP_KERNEL & ~gfp_notmask);
if (unlikely(status)) {
page_cache_release(page);
if (status == -EEXIST)
@@ -2161,7 +2166,7 @@ repeat:
}
return page;
}
-EXPORT_SYMBOL(__grab_cache_page);
+EXPORT_SYMBOL(grab_cache_page_write_begin);
static ssize_t generic_perform_write(struct file *file,
struct iov_iter *i, loff_t pos)