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Modify vdev_elevator_switch() to use elevator_change()

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As of Linux 2.6.36 an elevator_change() interface was added.
This commit updates vdev_elevator_switch() to use this interface
when available, otherwise it falls back to the usermodehelper
method.

Original-patch-by: foobarz <sysop@xeon.(none)>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #906
This commit is contained in:
Brian Behlendorf 2012-08-27 03:38:06 +07:00
parent 2f342404c1
commit 6d1d976b2c
3 changed files with 49 additions and 18 deletions
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25
config/kernel-elevator-change.m4 Normal file
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@ -0,0 +1,25 @@
dnl #
dnl # 2.6.36 API change
dnl # Verify the elevator_change() symbol is available.
dnl #
AC_DEFUN([ZFS_AC_KERNEL_ELEVATOR_CHANGE], [
AC_MSG_CHECKING([whether elevator_change() is available])
tmp_flags="$EXTRA_KCFLAGS"
EXTRA_KCFLAGS="-Wno-unused-but-set-variable"
ZFS_LINUX_TRY_COMPILE([
#include <linux/blkdev.h>
#include <linux/elevator.h>
],[
int ret;
struct request_queue *q = NULL;
char *elevator = NULL;
ret = elevator_change(q, elevator);
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_ELEVATOR_CHANGE, 1,
[elevator_change() is available])
],[
AC_MSG_RESULT(no)
])
EXTRA_KCFLAGS="$tmp_flags"
])

1
config/kernel.m4
View File

@ -67,6 +67,7 @@ AC_DEFUN([ZFS_AC_CONFIG_KERNEL], [
ZFS_AC_KERNEL_BDI
ZFS_AC_KERNEL_BDI_SETUP_AND_REGISTER
ZFS_AC_KERNEL_SET_NLINK
ZFS_AC_KERNEL_ELEVATOR_CHANGE
AS_IF([test "$LINUX_OBJ" != "$LINUX"], [
KERNELMAKE_PARAMS="$KERNELMAKE_PARAMS O=$LINUX_OBJ"

37
module/zfs/vdev_disk.c
View File

@ -111,19 +111,7 @@ vdev_disk_error(zio_t *zio)
* elevator to do the maximum front/back merging allowed by the
* physical device. This yields the largest possible requests for
* the device with the lowest total overhead.
*
* Unfortunately we cannot directly call the elevator_switch() function
* because it is not exported from the block layer. This means we have
* to use the sysfs interface and a user space upcall. Pools will be
* automatically imported on module load so we must do this at device
* open time from the kernel.
*/
#define SET_SCHEDULER_CMD \
"exec 0</dev/null " \
" 1>/sys/block/%s/queue/scheduler " \
" 2>/dev/null; " \
"echo %s"
static int
vdev_elevator_switch(vdev_t *v, char *elevator)
{
@ -131,8 +119,6 @@ vdev_elevator_switch(vdev_t *v, char *elevator)
struct block_device *bdev = vd->vd_bdev;
struct request_queue *q = bdev_get_queue(bdev);
char *device = bdev->bd_disk->disk_name;
char *argv[] = { "/bin/sh", "-c", NULL, NULL };
char *envp[] = { NULL };
int error;
/* Skip devices which are not whole disks (partitions) */
@ -147,14 +133,33 @@ vdev_elevator_switch(vdev_t *v, char *elevator)
if (!strncmp(elevator, "none", 4) && (strlen(elevator) == 4))
return (0);
#ifdef HAVE_ELEVATOR_CHANGE
error = elevator_change(q, elevator);
#else
/* For pre-2.6.36 kernels elevator_change() is not available.
* Therefore we fall back to using a usermodehelper to echo the
* elevator into sysfs; This requires /bin/echo and sysfs to be
* mounted which may not be true early in the boot process.
*/
# define SET_SCHEDULER_CMD \
"exec 0</dev/null " \
" 1>/sys/block/%s/queue/scheduler " \
" 2>/dev/null; " \
"echo %s"
{
char *argv[] = { "/bin/sh", "-c", NULL, NULL };
char *envp[] = { NULL };
argv[2] = kmem_asprintf(SET_SCHEDULER_CMD, device, elevator);
error = call_usermodehelper(argv[0], argv, envp, 1);
strfree(argv[2]);
}
#endif /* HAVE_ELEVATOR_CHANGE */
if (error)
printk("ZFS: Unable to set \"%s\" scheduler for %s (%s): %d\n",
elevator, v->vdev_path, device, error);
strfree(argv[2]);
return (error);
}