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    Subject[PATCH 4.9 19/63] dm thin: stop no_space_timeout worker when switching to write-mode
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

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

    From: Hou Tao <houtao1@huawei.com>

    commit 75294442d896f2767be34f75aca7cc2b0d01301f upstream.

    Now both check_for_space() and do_no_space_timeout() will read & write
    pool->pf.error_if_no_space. If these functions run concurrently, as
    shown in the following case, the default setting of "queue_if_no_space"
    can get lost.

    precondition:
    * error_if_no_space = false (aka "queue_if_no_space")
    * pool is in Out-of-Data-Space (OODS) mode
    * no_space_timeout worker has been queued

    CPU 0: CPU 1:
    // delete a thin device
    process_delete_mesg()
    // check_for_space() invoked by commit()
    set_pool_mode(pool, PM_WRITE)
    pool->pf.error_if_no_space = \
    pt->requested_pf.error_if_no_space

    // timeout, pool is still in OODS mode
    do_no_space_timeout
    // "queue_if_no_space" config is lost
    pool->pf.error_if_no_space = true
    pool->pf.mode = new_mode

    Fix it by stopping no_space_timeout worker when switching to write mode.

    Fixes: bcc696fac11f ("dm thin: stay in out-of-data-space mode once no_space_timeout expires")
    Cc: stable@vger.kernel.org
    Signed-off-by: Hou Tao <houtao1@huawei.com>
    Signed-off-by: Mike Snitzer <snitzer@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/md/dm-thin.c | 2 ++
    1 file changed, 2 insertions(+)

    --- a/drivers/md/dm-thin.c
    +++ b/drivers/md/dm-thin.c
    @@ -2518,6 +2518,8 @@ static void set_pool_mode(struct pool *p
    case PM_WRITE:
    if (old_mode != new_mode)
    notify_of_pool_mode_change(pool, "write");
    + if (old_mode == PM_OUT_OF_DATA_SPACE)
    + cancel_delayed_work_sync(&pool->no_space_timeout);
    pool->out_of_data_space = false;
    pool->pf.error_if_no_space = pt->requested_pf.error_if_no_space;
    dm_pool_metadata_read_write(pool->pmd);

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