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authorMikulas Patocka <mpatocka@redhat.com>2012-06-03 00:29:58 +0100
committerAlasdair G Kergon <agk@redhat.com>2012-06-03 00:29:58 +0100
commit35991652baa12ff3d0e420c0d0cb2ad9f7076e5b (patch)
tree82d6d2bbd03be95dfb91e0678a94b613cbfc28ae
parentf220fd4efb334a772f9a14b2372175f38d89355e (diff)
downloadconfigs-35991652baa12ff3d0e420c0d0cb2ad9f7076e5b.tar.gz
dm mpath: allow ioctls to trigger pg init
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>
-rw-r--r--drivers/md/dm-mpath.c26
1 files changed, 17 insertions, 9 deletions
diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index 2469ba68dc2..638dae048b4 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -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,