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Expose zfs_vdev_open_timeout_ms as a tunable 

Some of our customers have been occasionally hitting zfs import failures
in Linux because udevd doesn't create the by-id symbolic links in time
for zpool import to use them. The main issue is that the
systemd-udev-settle.service that zfs-import-cache.service and other
services depend on is racy. There is also an openzfs issue filed (see
https://github.com/openzfs/zfs/issues/10891) outlining the problem and
potential solutions.

With the proper solutions being significant in terms of complexity and
the priority of the issue being low for the time being, this patch
exposes `zfs_vdev_open_timeout_ms` as a tunable so people that are
experiencing this issue often can increase it as a workaround.

Reviewed-by: Matthew Ahrens <mahrens@delphix.com>
Reviewed-by: Richard Yao <richard.yao@alumni.stonybrook.edu>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Don Brady <don.brady@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Serapheim Dimitropoulos <serapheim@delphix.com>
Closes #14133
This commit is contained in:
Serapheim Dimitropoulos 2022-11-03 15:02:46 -07:00 committed by GitHub
parent 595d3ac2ed
commit f66ffe6878
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2 changed files with 11 additions and 1 deletions
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7
man/man4/zfs.4
View File

@ -1249,6 +1249,13 @@ Ideally, this will be at least the sum of each queue's
.Sy max_active .
.No See Sx ZFS I/O SCHEDULER .
.
.It Sy zfs_vdev_open_timeout_ms Ns = Ns Sy 1000 Pq uint
Timeout value to wait before determining a device is missing
during import.
This is helpful for transient missing paths due
to links being briefly removed and recreated in response to
udev events.
.
.It Sy zfs_vdev_rebuild_max_active Ns = Ns Sy 3 Pq uint
Maximum sequential resilver I/O operations active to each device.
.No See Sx ZFS I/O SCHEDULER .

5
module/os/linux/zfs/vdev_disk.c
View File

@ -56,7 +56,7 @@ static void *zfs_vdev_holder = VDEV_HOLDER;
* device is missing. The missing path may be transient since the links
* can be briefly removed and recreated in response to udev events.
*/
static unsigned zfs_vdev_open_timeout_ms = 1000;
static uint_t zfs_vdev_open_timeout_ms = 1000;
/*
* Size of the "reserved" partition, in blocks.
@ -1042,3 +1042,6 @@ param_set_max_auto_ashift(const char *buf, zfs_kernel_param_t *kp)
return (0);
}
ZFS_MODULE_PARAM(zfs_vdev, zfs_vdev_, open_timeout_ms, UINT, ZMOD_RW,
"Timeout before determining that a device is missing");