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    Subject[PATCH 4.14 081/138] tcmu: release blocks for partially setup cmds
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

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

    From: Mike Christie <mchristi@redhat.com>


    [ Upstream commit 810b8153c4243d2012a6ec002ddd3bbc9a9ae8c2 ]

    If we cannot setup a cmd because we run out of ring space
    or global pages release the blocks before sleeping. This
    prevents a deadlock where dev0 has waiting_blocks set and
    needs N blocks, but dev1 to devX have each allocated N / X blocks
    and also hit the global block limit so they went to sleep.

    find_free_blocks is not able to take the sleeping dev's
    blocks becaause their waiting_blocks is set and even
    if it was not the block returned by find_last_bit could equal
    dbi_max. The latter will probably never happen because
    DATA_BLOCK_BITS is so high but in the next patches
    DATA_BLOCK_BITS and TCMU_GLOBAL_MAX_BLOCKS will be settable so
    it might be lower and could happen.

    Signed-off-by: Mike Christie <mchristi@redhat.com>
    Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/target/target_core_user.c | 7 +++++++
    1 file changed, 7 insertions(+)

    --- a/drivers/target/target_core_user.c
    +++ b/drivers/target/target_core_user.c
    @@ -796,6 +796,13 @@ tcmu_queue_cmd_ring(struct tcmu_cmd *tcm
    int ret;
    DEFINE_WAIT(__wait);

    + /*
    + * Don't leave commands partially setup because the unmap
    + * thread might need the blocks to make forward progress.
    + */
    + tcmu_cmd_free_data(tcmu_cmd, tcmu_cmd->dbi_cur);
    + tcmu_cmd_reset_dbi_cur(tcmu_cmd);
    +
    prepare_to_wait(&udev->wait_cmdr, &__wait, TASK_INTERRUPTIBLE);

    pr_debug("sleeping for ring space\n");

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