• Johannes Weiner's avatar
    mm: filemap: fix mapping->nrpages double accounting in fuse · 3ddf40e8
    Johannes Weiner authored
    Commit 22f2ac51 ("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: 22f2ac51 ("mm: workingset: fix crash in shadow node shrinker caused by replace_page_cache_page()")
    Signed-off-by: default avatarJohannes 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: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    3ddf40e8
filemap.c 77.3 KB