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authorJohannes Weiner <hannes@cmpxchg.org>2016-10-04 17:58:06 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2016-10-05 19:17:56 +0300
commit3ddf40e8c31964b744ff10abb48c8e36a83ec6e7 (patch)
tree68aa25b117a4dd307eb4923e02074f85a5c961f0
parentd3798ae8c6f3767c726403c2ca6ecc317752c9dd (diff)
downloadlinux-3ddf40e8c31964b744ff10abb48c8e36a83ec6e7.tar.xz
mm: filemap: fix mapping->nrpages double accounting in fuse
Commit 22f2ac51b6d6 ("mm: workingset: fix crash in shadow node shrinker caused by replace_page_cache_page()") switched replace_page_cache() from raw radix tree operations to page_cache_tree_insert() but didn't take into account that the latter function, unlike the raw radix tree op, handles mapping->nrpages. As a result, that counter is bumped for each page replacement rather than balanced out even. The mapping->nrpages counter is used to skip needless radix tree walks when invalidating, truncating, syncing inodes without pages, as well as statistics for userspace. Since the error is positive, we'll do more page cache tree walks than necessary; we won't miss a necessary one. And we'll report more buffer pages to userspace than there are. The error is limited to fuse inodes. Fixes: 22f2ac51b6d6 ("mm: workingset: fix crash in shadow node shrinker caused by replace_page_cache_page()") Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Miklos Szeredi <miklos@szeredi.hu> Cc: stable@vger.kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/filemap.c1
1 files changed, 0 insertions, 1 deletions
diff --git a/mm/filemap.c b/mm/filemap.c
index 96b9e9c30630..4bad32dd4b3b 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -633,7 +633,6 @@ int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
__delete_from_page_cache(old, NULL);
error = page_cache_tree_insert(mapping, new, NULL);
BUG_ON(error);
- mapping->nrpages++;
/*
* hugetlb pages do not participate in page cache accounting.