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Linux 5.13 compat: retry zvol_open() when contended

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Due to a possible lock inversion the zvol open call path on Linux
needs to be able to retry in the case where the spa_namespace_lock
cannot be acquired.

For Linux 5.12 an older kernel this was accomplished by returning
-ERESTARTSYS from zvol_open() to request that blkdev_get() drop
the bdev->bd_mutex lock, reaquire it, then call the open callback
again.  However, as of the 5.13 kernel this behavior was removed.

Therefore, for 5.12 and older kernels we preserved the existing
retry logic, but for 5.13 and newer kernels we retry internally in
zvol_open().  This should always succeed except in the case where
a pool's vdev are layed on zvols, in which case it may fail.  To
handle this case vdev_disk_open() has been updated to retry when
opening a device when -ERESTARTSYS is returned.

Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Tony Nguyen <tony.nguyen@delphix.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #12301
Closes #12759
This commit is contained in:
Brian Behlendorf
2021-12-01 16:07:12 -08:00
committed by Tony Hutter
parent 3c97d7a84b
commit 2915930f89
4 changed files with 90 additions and 37 deletions
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config/kernel-blkdev.m4
+22
View File
@@ -294,6 +294,27 @@ AC_DEFUN([ZFS_AC_KERNEL_BLKDEV_BDEV_WHOLE], [
])
])
dnl #
dnl # 5.13 API change
dnl # blkdev_get_by_path() no longer handles ERESTARTSYS
dnl #
dnl # Unfortunately we're forced to rely solely on the kernel version
dnl # number in order to determine the expected behavior. This was an
dnl # internal change to blkdev_get_by_dev(), see commit a8ed1a0607.
dnl #
AC_DEFUN([ZFS_AC_KERNEL_BLKDEV_GET_ERESTARTSYS], [
AC_MSG_CHECKING([whether blkdev_get_by_path() handles ERESTARTSYS])
AS_VERSION_COMPARE([$LINUX_VERSION], [5.13.0], [
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_BLKDEV_GET_ERESTARTSYS, 1,
[blkdev_get_by_path() handles ERESTARTSYS])
],[
AC_MSG_RESULT(no)
],[
AC_MSG_RESULT(no)
])
])
AC_DEFUN([ZFS_AC_KERNEL_SRC_BLKDEV], [
ZFS_AC_KERNEL_SRC_BLKDEV_GET_BY_PATH
ZFS_AC_KERNEL_SRC_BLKDEV_PUT
@@ -318,4 +339,5 @@ AC_DEFUN([ZFS_AC_KERNEL_BLKDEV], [
ZFS_AC_KERNEL_BLKDEV_CHECK_DISK_CHANGE
ZFS_AC_KERNEL_BLKDEV_BDEV_CHECK_MEDIA_CHANGE
ZFS_AC_KERNEL_BLKDEV_BDEV_WHOLE
ZFS_AC_KERNEL_BLKDEV_GET_ERESTARTSYS
])