releases/4.15.17/tcmu-release-blocks-for-partially-setup-cmds.patch

   1 From foo@baz Mon Apr  9 10:16:32 CEST 2018
   2 From: Mike Christie <mchristi@redhat.com>
   3 Date: Tue, 28 Nov 2017 12:40:33 -0600
   4 Subject: tcmu: release blocks for partially setup cmds
   5
   6 From: Mike Christie <mchristi@redhat.com>
   7
   8
   9 [ Upstream commit 810b8153c4243d2012a6ec002ddd3bbc9a9ae8c2 ]
  10
  11 If we cannot setup a cmd because we run out of ring space
  12 or global pages release the blocks before sleeping. This
  13 prevents a deadlock where dev0 has waiting_blocks set and
  14 needs N blocks, but dev1 to devX have each allocated N / X blocks
  15 and also hit the global block limit so they went to sleep.
  16
  17 find_free_blocks is not able to take the sleeping dev's
  18 blocks becaause their waiting_blocks is set and even
  19 if it was not the block returned by find_last_bit could equal
  20 dbi_max. The latter will probably never happen because
  21 DATA_BLOCK_BITS is so high but in the next patches
  22 DATA_BLOCK_BITS and TCMU_GLOBAL_MAX_BLOCKS will be settable so
  23 it might be lower and could happen.
  24
  25 Signed-off-by: Mike Christie <mchristi@redhat.com>
  26 Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
  27 Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
  28 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  29 ---
  30  drivers/target/target_core_user.c |    7 +++++++
  31  1 file changed, 7 insertions(+)
  32
  33 --- a/drivers/target/target_core_user.c
  34 +++ b/drivers/target/target_core_user.c
  35 @@ -805,6 +805,13 @@ tcmu_queue_cmd_ring(struct tcmu_cmd *tcm
  36                 int ret;
  37                 DEFINE_WAIT(__wait);
  38
  39 +               /*
  40 +                * Don't leave commands partially setup because the unmap
  41 +                * thread might need the blocks to make forward progress.
  42 +                */
  43 +               tcmu_cmd_free_data(tcmu_cmd, tcmu_cmd->dbi_cur);
  44 +               tcmu_cmd_reset_dbi_cur(tcmu_cmd);
  45 +
  46                 prepare_to_wait(&udev->wait_cmdr, &__wait, TASK_INTERRUPTIBLE);
  47
  48                 pr_debug("sleeping for ring space\n");