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    Subject[PATCH 4.20 40/80] fs/dcache: Fix incorrect nr_dentry_unused accounting in shrink_dcache_sb()
    Date
    4.20-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Waiman Long <longman@redhat.com>

    commit 1dbd449c9943e3145148cc893c2461b72ba6fef0 upstream.

    The nr_dentry_unused per-cpu counter tracks dentries in both the LRU
    lists and the shrink lists where the DCACHE_LRU_LIST bit is set.

    The shrink_dcache_sb() function moves dentries from the LRU list to a
    shrink list and subtracts the dentry count from nr_dentry_unused. This
    is incorrect as the nr_dentry_unused count will also be decremented in
    shrink_dentry_list() via d_shrink_del().

    To fix this double decrement, the decrement in the shrink_dcache_sb()
    function is taken out.

    Fixes: 4e717f5c1083 ("list_lru: remove special case function list_lru_dispose_all."
    Cc: stable@kernel.org
    Signed-off-by: Waiman Long <longman@redhat.com>
    Reviewed-by: Dave Chinner <dchinner@redhat.com>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/dcache.c | 6 +-----
    1 file changed, 1 insertion(+), 5 deletions(-)

    --- a/fs/dcache.c
    +++ b/fs/dcache.c
    @@ -1188,15 +1188,11 @@ static enum lru_status dentry_lru_isolat
    */
    void shrink_dcache_sb(struct super_block *sb)
    {
    - long freed;
    -
    do {
    LIST_HEAD(dispose);

    - freed = list_lru_walk(&sb->s_dentry_lru,
    + list_lru_walk(&sb->s_dentry_lru,
    dentry_lru_isolate_shrink, &dispose, 1024);
    -
    - this_cpu_sub(nr_dentry_unused, freed);
    shrink_dentry_list(&dispose);
    } while (list_lru_count(&sb->s_dentry_lru) > 0);
    }

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