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    Subject[PATCH 4.4 76/91] Btrfs: adjust outstanding_extents counter properly when dio write is split
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

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

    From: Liu Bo <bo.li.liu@oracle.com>


    [ Upstream commit c2931667c83ded6504b3857e99cc45b21fa496fb ]

    Currently how btrfs dio deals with split dio write is not good
    enough if dio write is split into several segments due to the
    lack of contiguous space, a large dio write like 'dd bs=1G count=1'
    can end up with incorrect outstanding_extents counter and endio
    would complain loudly with an assertion.

    This fixes the problem by compensating the outstanding_extents
    counter in inode if a large dio write gets split.

    Reported-by: Anand Jain <anand.jain@oracle.com>
    Tested-by: Anand Jain <anand.jain@oracle.com>
    Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
    Signed-off-by: David Sterba <dsterba@suse.com>
    Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    fs/btrfs/inode.c | 11 +++++++++--
    1 file changed, 9 insertions(+), 2 deletions(-)

    --- a/fs/btrfs/inode.c
    +++ b/fs/btrfs/inode.c
    @@ -7521,11 +7521,18 @@ static void adjust_dio_outstanding_exten
    * within our reservation, otherwise we need to adjust our inode
    * counter appropriately.
    */
    - if (dio_data->outstanding_extents) {
    + if (dio_data->outstanding_extents >= num_extents) {
    dio_data->outstanding_extents -= num_extents;
    } else {
    + /*
    + * If dio write length has been split due to no large enough
    + * contiguous space, we need to compensate our inode counter
    + * appropriately.
    + */
    + u64 num_needed = num_extents - dio_data->outstanding_extents;
    +
    spin_lock(&BTRFS_I(inode)->lock);
    - BTRFS_I(inode)->outstanding_extents += num_extents;
    + BTRFS_I(inode)->outstanding_extents += num_needed;
    spin_unlock(&BTRFS_I(inode)->lock);
    }
    }

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