dm mpath: allow ioctls to trigger pg init (35991652) · Commits · 戴 / test

After the failure of a group of paths, any alternative paths that need initialising do not become available until further I/O is sent to the device. Until this has happened, ioctls return -EAGAIN. With this patch, new paths are made available in response to an ioctl too. The processing of the ioctl gets delayed until this has happened. Instead of returning an error, we submit a work item to kmultipathd (that will potentially activate the new path) and retry in ten milliseconds. Note that the patch doesn't retry an ioctl if the ioctl itself fails due to a path failure. Such retries should be handled intelligently by the code that generated the ioctl in the first place, noting that some SCSI commands should not be retried because they are not idempotent (XOR write commands). For commands that could be retried, there is a danger that if the device rejected the SCSI command, the path could be errorneously marked as failed, and the request would be retried on another path which might fail too. It can be determined if the failure happens on the device or on the SCSI controller, but there is no guarantee that all SCSI drivers set these flags correctly. Signed-off-by:

Mikulas Patocka <mpatocka@redhat.com> Signed-off-by:

Alasdair G Kergon <agk@redhat.com>

drivers/md/dm-mpath.c

+17 −9

Original line number	Diff line number	Diff line
		@@ -18,6 +18,7 @@
		#include <linux/slab.h>
		#include <linux/time.h>
		#include <linux/workqueue.h>
		#include <linux/delay.h>
		#include <scsi/scsi_dh.h>
		#include <linux/atomic.h>

		@@ -486,9 +487,6 @@ static void process_queued_ios(struct work_struct *work)

		spin_lock_irqsave(&m->lock, flags);

		if (!m->queue_size)
		goto out;

		if (!m->current_pgpath)
		__choose_pgpath(m, 0);

		@@ -501,7 +499,6 @@ static void process_queued_ios(struct work_struct *work)
		if (m->pg_init_required && !m->pg_init_in_progress && pgpath)
		__pg_init_all_paths(m);

		out:
		spin_unlock_irqrestore(&m->lock, flags);
		if (!must_queue)
		dispatch_queued_ios(m);
		@@ -1522,11 +1519,16 @@ out:
		static int multipath_ioctl(struct dm_target *ti, unsigned int cmd,
		unsigned long arg)
		{
		struct multipath m = (struct multipath ) ti->private;
		struct block_device *bdev = NULL;
		fmode_t mode = 0;
		struct multipath *m = ti->private;
		struct block_device *bdev;
		fmode_t mode;
		unsigned long flags;
		int r = 0;
		int r;

		again:
		bdev = NULL;
		mode = 0;
		r = 0;

		spin_lock_irqsave(&m->lock, flags);

		@@ -1551,6 +1553,12 @@ static int multipath_ioctl(struct dm_target *ti, unsigned int cmd,
		if (!r && ti->len != i_size_read(bdev->bd_inode) >> SECTOR_SHIFT)
		r = scsi_verify_blk_ioctl(NULL, cmd);

		if (r == -EAGAIN && !fatal_signal_pending(current)) {
		queue_work(kmultipathd, &m->process_queued_ios);
		msleep(10);
		goto again;
		}

		return r ? : __blkdev_driver_ioctl(bdev, mode, cmd, arg);
		}

		@@ -1648,7 +1656,7 @@ out:
		---------------------------------------------------------------/
		static struct target_type multipath_target = {
		.name = "multipath",
		.version = {1, 3, 0},
		.version = {1, 4, 0},
		.module = THIS_MODULE,
		.ctr = multipath_ctr,
		.dtr = multipath_dtr,

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