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authorFan Li <fanofcode.li@samsung.com>2015-08-18 17:13:13 +0800
committerJaegeuk Kim <jaegeuk@kernel.org>2015-08-21 22:45:06 -0700
commitf8b703da2c23f9bfda7299bd14e4f7201c2be3c8 (patch)
tree82fe2fc35b8597ed8659b67623b35045630e98c0 /fs/f2fs
parent217940d4f0c4ec4f0852f7046fa419d0edf65c17 (diff)
downloadop-kernel-dev-f8b703da2c23f9bfda7299bd14e4f7201c2be3c8.zip
op-kernel-dev-f8b703da2c23f9bfda7299bd14e4f7201c2be3c8.tar.gz
f2fs: fix to update cached_en of extent tree properly
In f2fs_lookup_extent_tree, et->cached_en was read and updated with only read lock held, it could cause __lookup_extent_tree within return entirely wrong extent_node, if other thread update et->cached_en just before __lookup_extent_tree return. However, there are two things about this patch that need to be noticed: 1. It does no good to arrange the order of concurrent read/write, the result would still be random in such case. 2. It's built on this assumption: the mix up of reads and writes on a single pointer would not make the pointer partially wrong at any time. Please let me know if I'm wrong, thx. Signed-off-by: Fan li <fanofcode.li@samsung.com> Reviewed-by: Chao Yu <chao2.yu@samsung.com> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Diffstat (limited to 'fs/f2fs')
-rw-r--r--fs/f2fs/extent_cache.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c
index 32fae8a..cea5813 100644
--- a/fs/f2fs/extent_cache.c
+++ b/fs/f2fs/extent_cache.c
@@ -85,13 +85,13 @@ static struct extent_node *__lookup_extent_tree(struct extent_tree *et,
unsigned int fofs)
{
struct rb_node *node = et->root.rb_node;
- struct extent_node *en;
+ struct extent_node *en = et->cached_en;
- if (et->cached_en) {
- struct extent_info *cei = &et->cached_en->ei;
+ if (en) {
+ struct extent_info *cei = &en->ei;
if (cei->fofs <= fofs && cei->fofs + cei->len > fofs)
- return et->cached_en;
+ return en;
}
while (node) {
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