On 05/10/2013 12:35 PM, Alasdair G Kergon wrote:
> On Fri, May 10, 2013 at 12:32:29PM +0200, Hannes Reinecke wrote:
>> "dm-multipath: Drop table when retrying ioctl"
>
> That one's not showing up: direct link or mail me it?
>
Here it is.
I _thought_ to have it sent to dm-devel, but apparently not.
Wonder what happened there...
Cheers,
Hannes
--
Dr. Hannes Reinecke zSeries & Storage
hare@xxxxxxx +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
>From 3e501ba7080d7913e85361ea0cef5b5c8fd1f153 Mon Sep 17 00:00:00 2001
From: Hannes Reinecke <hare@xxxxxxx>
Date: Tue, 23 Apr 2013 12:33:52 +0200
Subject: [PATCH] dm-multipath: Drop table when retrying ioctl
When multipath needs to retry an ioctl the reference to the
current live table needs to be dropped. Otherwise a deadlock
occurs when all paths are down:
- dm_blk_ioctl takes a reference to the current table
and spins in multipath_iotcl().
- A new table is being loaded, but upon resume the process
hangs in dm_table_destroy() waiting for references to
drop to zero.
With this patch the reference to the old table is dropped
prior to retry, thereby avoiding the deadlock.
Cc: Alasdair Kergon <agk@xxxxxxxxxx>
Cc: Mike Snitzer <snitzer@xxxxxxxxxx>
Signed-off-by: Hannes Reinecke <hare@xxxxxxx>
diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index 51bb816..fb27edc 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -1578,7 +1578,7 @@ again:
}
if ((pgpath && m->queue_io) || (!pgpath && m->queue_if_no_path))
- r = -EAGAIN;
+ r = -ENOTCONN;
else if (!bdev)
r = -EIO;
@@ -1590,11 +1590,8 @@ again:
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)) {
+ if (r == -ENOTCONN && !fatal_signal_pending(current))
queue_work(kmultipathd, &m->process_queued_ios);
- msleep(10);
- goto again;
- }
return r ? : __blkdev_driver_ioctl(bdev, mode, cmd, arg);
}
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 9a0bdad..cd749bf 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -388,10 +388,12 @@ static int dm_blk_ioctl(struct block_device *bdev, fmode_t mode,
unsigned int cmd, unsigned long arg)
{
struct mapped_device *md = bdev->bd_disk->private_data;
- struct dm_table *map = dm_get_live_table(md);
+ struct dm_table *map;
struct dm_target *tgt;
int r = -ENOTTY;
+retry:
+ map = dm_get_live_table(md);
if (!map || !dm_table_get_size(map))
goto out;
@@ -412,6 +414,11 @@ static int dm_blk_ioctl(struct block_device *bdev, fmode_t mode,
out:
dm_table_put(map);
+ if (r == -ENOTCONN) {
+ msleep(10);
+ goto retry;
+ }
+
return r;
}
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