zvol: Temporally disable blk-mq

There was a report of zvol data loss (#15351) after enabling blk-mq on a
zvol backed with 16k physical block sized disks.  Out of an abundance of
caution, do not allow the user to enable blk-mq until we can look into
the issue.

Note that blk-mq was not enabled by default on zvols.  It was always
opt-in via the zvol_use_blk_mq module parameter.

Reviewed-by: Brian Behlendorf <[email protected]>
Reviewed-by: Tony Nguyen <[email protected]>
Signed-off-by: Tony Hutter <[email protected]>
Addresses: #15351
Closes #15378 

1 files changed, 0 insertions, 57 deletions

diff --git a/man/man4/zfs.4 b/man/man4/zfs.4
index cfadd79d8..71a3e67ee 100644
--- a/man/man4/zfs.4
+++ b/man/man4/zfs.4
@@ -2317,63 +2317,6 @@ If
 .Sy zvol_threads
 to the number of CPUs present or 32 (whichever is greater).
 .
-.It Sy zvol_blk_mq_threads Ns = Ns Sy 0 Pq uint
-The number of threads per zvol to use for queuing IO requests.
-This parameter will only appear if your kernel supports
-.Li blk-mq
-and is only read and assigned to a zvol at zvol load time.
-If
-.Sy 0
-(the default) then internally set
-.Sy zvol_blk_mq_threads
-to the number of CPUs present.
-.
-.It Sy zvol_use_blk_mq Ns = Ns Sy 0 Ns | Ns 1 Pq uint
-Set to
-.Sy 1
-to use the
-.Li blk-mq
-API for zvols.
-Set to
-.Sy 0
-(the default) to use the legacy zvol APIs.
-This setting can give better or worse zvol performance depending on
-the workload.
-This parameter will only appear if your kernel supports
-.Li blk-mq
-and is only read and assigned to a zvol at zvol load time.
-.
-.It Sy zvol_blk_mq_blocks_per_thread Ns = Ns Sy 8 Pq uint
-If
-.Sy zvol_use_blk_mq
-is enabled, then process this number of
-.Sy volblocksize Ns -sized blocks per zvol thread.
-This tunable can be use to favor better performance for zvol reads (lower
-values) or writes (higher values).
-If set to
-.Sy 0 ,
-then the zvol layer will process the maximum number of blocks
-per thread that it can.
-This parameter will only appear if your kernel supports
-.Li blk-mq
-and is only applied at each zvol's load time.
-.
-.It Sy zvol_blk_mq_queue_depth Ns = Ns Sy 0 Pq uint
-The queue_depth value for the zvol
-.Li blk-mq
-interface.
-This parameter will only appear if your kernel supports
-.Li blk-mq
-and is only applied at each zvol's load time.
-If
-.Sy 0
-(the default) then use the kernel's default queue depth.
-Values are clamped to the kernel's
-.Dv BLKDEV_MIN_RQ
-and
-.Dv BLKDEV_MAX_RQ Ns / Ns Dv BLKDEV_DEFAULT_RQ
-limits.
-.
 .It Sy zvol_volmode Ns = Ns Sy 1 Pq uint
 Defines zvol block devices behaviour when
 .Sy volmode Ns = Ns Sy default :