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Fix synchronous behavior in __vdev_disk_physio()

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Commit b39c22b set the READ_SYNC and WRITE_SYNC flags for a bio
based on the ZIO_PRIORITY_* flag passed in.  This had the unnoticed
side-effect of making the vdev_disk_io_start() synchronous for
certain I/Os.

This in turn resulted in vdev_disk_io_start() being able to
re-dispatch zio's which would result in a RCU stalls when a disk
was removed from the system.  Additionally, this could negatively
impact performance and explains the performance regressions reported
in both #3829 and #3780.

This patch resolves the issue by making the blocking behavior
dependent on a 'wait' flag being passed rather than overloading
the passed bio flags.

Finally, the WRITE_SYNC and READ_SYNC behavior is restricted to
non-rotational devices where there is no benefit to queuing to
aggregate the I/O.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #3652
Issue #3780
Issue #3785
Issue #3817
Issue #3821
Issue #3829
Issue #3832
Issue #3870
This commit is contained in:
Brian Behlendorf
2015-09-24 16:32:25 -07:00
parent ef5b2e1048
commit 5592404784
3 changed files with 8 additions and 81 deletions
Download Patch File Download Diff File Expand all files Collapse all files
config/kernel-bio-rw-syncio.m4
-50
View File
@@ -1,50 +0,0 @@
dnl #
dnl # Preferred interface for flagging a synchronous bio:
dnl # 2.6.12-2.6.29: BIO_RW_SYNC
dnl # 2.6.30-2.6.35: BIO_RW_SYNCIO
dnl # 2.6.36-2.6.xx: REQ_SYNC
dnl #
AC_DEFUN([ZFS_AC_KERNEL_BIO_RW_SYNC], [
AC_MSG_CHECKING([whether BIO_RW_SYNC is defined])
ZFS_LINUX_TRY_COMPILE([
#include <linux/bio.h>
],[
int flags __attribute__ ((unused));
flags = BIO_RW_SYNC;
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_BIO_RW_SYNC, 1, [BIO_RW_SYNC is defined])
],[
AC_MSG_RESULT(no)
])
])
AC_DEFUN([ZFS_AC_KERNEL_BIO_RW_SYNCIO], [
AC_MSG_CHECKING([whether BIO_RW_SYNCIO is defined])
ZFS_LINUX_TRY_COMPILE([
#include <linux/bio.h>
],[
int flags __attribute__ ((unused));
flags = BIO_RW_SYNCIO;
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_BIO_RW_SYNCIO, 1, [BIO_RW_SYNCIO is defined])
],[
AC_MSG_RESULT(no)
])
])
AC_DEFUN([ZFS_AC_KERNEL_REQ_SYNC], [
AC_MSG_CHECKING([whether REQ_SYNC is defined])
ZFS_LINUX_TRY_COMPILE([
#include <linux/bio.h>
],[
int flags __attribute__ ((unused));
flags = REQ_SYNC;
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_REQ_SYNC, 1, [REQ_SYNC is defined])
],[
AC_MSG_RESULT(no)
])
])
config/kernel.m4
-3
View File
@@ -25,9 +25,6 @@ AC_DEFUN([ZFS_AC_CONFIG_KERNEL], [
ZFS_AC_KERNEL_BIO_END_IO_T_ARGS
ZFS_AC_KERNEL_BIO_RW_BARRIER
ZFS_AC_KERNEL_BIO_RW_DISCARD
ZFS_AC_KERNEL_BIO_RW_SYNC
ZFS_AC_KERNEL_BIO_RW_SYNCIO
ZFS_AC_KERNEL_REQ_SYNC
ZFS_AC_KERNEL_BLK_QUEUE_FLUSH
ZFS_AC_KERNEL_BLK_QUEUE_MAX_HW_SECTORS
ZFS_AC_KERNEL_BLK_QUEUE_MAX_SEGMENTS