116 lines
4.2 KiB
Diff
116 lines
4.2 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Brian Behlendorf <behlendorf1@llnl.gov>
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Date: Tue, 19 Jun 2018 21:52:45 -0700
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Subject: [PATCH] Linux 4.14 compat: blk_queue_stackable()
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The blk_queue_stackable() function was replaced in the 4.14 kernel
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by queue_is_rq_based(), commit torvalds/linux@5fdee212. This change
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resulted in the default elevator being used which can negatively
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impact performance.
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Rather than adding additional compatibility code to detect the
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new interface unconditionally attempt to set the elevator. Since
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we expect this to fail for block devices without an elevator the
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error message has been moved in to zfs_dbgmsg().
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Finally, it was observed that the elevator_change() was removed
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from the 4.12 kernel, commit torvalds/linux@c033269. Update the
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comment to clearly specify which are expected to export the
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elevator_change() symbol.
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Reviewed-by: Matthew Ahrens <mahrens@delphix.com>
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Reviewed-by: Tony Hutter <hutter2@llnl.gov>
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Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
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Closes #7645
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Signed-off-by: Stoiko Ivanov <s.ivanov@proxmox.com>
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---
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config/kernel-elevator-change.m4 | 4 ++--
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include/linux/blkdev_compat.h | 11 -----------
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module/zfs/vdev_disk.c | 22 ++++++++++------------
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3 files changed, 12 insertions(+), 25 deletions(-)
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diff --git a/config/kernel-elevator-change.m4 b/config/kernel-elevator-change.m4
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index ace5aa82..eba25257 100644
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--- a/config/kernel-elevator-change.m4
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+++ b/config/kernel-elevator-change.m4
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@@ -1,6 +1,6 @@
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dnl #
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-dnl # 2.6.36 API change
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-dnl # Verify the elevator_change() symbol is available.
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+dnl # 2.6.36 API, exported elevator_change() symbol
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+dnl # 4.12 API, removed elevator_change() symbol
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dnl #
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AC_DEFUN([ZFS_AC_KERNEL_ELEVATOR_CHANGE], [
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AC_MSG_CHECKING([whether elevator_change() is available])
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diff --git a/include/linux/blkdev_compat.h b/include/linux/blkdev_compat.h
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index 27f05662..c8cdf38e 100644
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--- a/include/linux/blkdev_compat.h
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+++ b/include/linux/blkdev_compat.h
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@@ -106,17 +106,6 @@ blk_queue_set_write_cache(struct request_queue *q, bool wc, bool fua)
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#endif
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/*
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- * 2.6.27 API change,
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- * The blk_queue_stackable() queue flag was added in 2.6.27 to handle dm
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- * stacking drivers. Prior to this request stacking drivers were detected
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- * by checking (q->request_fn == NULL), for earlier kernels we revert to
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- * this legacy behavior.
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- */
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-#ifndef blk_queue_stackable
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-#define blk_queue_stackable(q) ((q)->request_fn == NULL)
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-#endif
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-
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-/*
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* 2.6.34 API change,
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* The blk_queue_max_hw_sectors() function replaces blk_queue_max_sectors().
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*/
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diff --git a/module/zfs/vdev_disk.c b/module/zfs/vdev_disk.c
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index 6dc0544f..c5708cb2 100644
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--- a/module/zfs/vdev_disk.c
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+++ b/module/zfs/vdev_disk.c
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@@ -168,23 +168,20 @@ vdev_elevator_switch(vdev_t *v, char *elevator)
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if (!v->vdev_wholedisk && strncmp(device, "dm-", 3) != 0)
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return;
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- /* Skip devices without schedulers (loop, ram, dm, etc) */
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- if (!q->elevator || !blk_queue_stackable(q))
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- return;
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-
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/* Leave existing scheduler when set to "none" */
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if ((strncmp(elevator, "none", 4) == 0) && (strlen(elevator) == 4))
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return;
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+ /*
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+ * The elevator_change() function was available in kernels from
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+ * 2.6.36 to 4.11. When not available fall back to using the user
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+ * mode helper functionality to set the elevator via sysfs. This
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+ * requires /bin/echo and sysfs to be mounted which may not be true
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+ * early in the boot process.
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+ */
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#ifdef HAVE_ELEVATOR_CHANGE
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error = elevator_change(q, elevator);
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#else
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- /*
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- * For pre-2.6.36 kernels elevator_change() is not available.
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- * Therefore we fall back to using a usermodehelper to echo the
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- * elevator into sysfs; This requires /bin/echo and sysfs to be
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- * mounted which may not be true early in the boot process.
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- */
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#define SET_SCHEDULER_CMD \
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"exec 0</dev/null " \
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" 1>/sys/block/%s/queue/scheduler " \
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@@ -198,9 +195,10 @@ vdev_elevator_switch(vdev_t *v, char *elevator)
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error = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_PROC);
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strfree(argv[2]);
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#endif /* HAVE_ELEVATOR_CHANGE */
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- if (error)
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- printk("ZFS: Unable to set \"%s\" scheduler for %s (%s): %d\n",
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+ if (error) {
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+ zfs_dbgmsg("Unable to set \"%s\" scheduler for %s (%s): %d\n",
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elevator, v->vdev_path, device, error);
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+ }
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}
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/*
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