From f8b703da2c23f9bfda7299bd14e4f7201c2be3c8 Mon Sep 17 00:00:00 2001 From: Fan Li Date: Tue, 18 Aug 2015 17:13:13 +0800 Subject: 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 Reviewed-by: Chao Yu Signed-off-by: Jaegeuk Kim --- fs/f2fs/extent_cache.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c index 32fae8ad5b7e..cea581353bc2 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) { -- cgit v1.2.3