4.15-stable review patch. If anyone has any objections, please let me know.
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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 @@ -805,6 +805,13 @@ 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");