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>
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 @@
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) {