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authorJun'ichi Nomura <j-nomura@ce.jp.nec.com>2007-01-26 00:57:07 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-01-26 13:51:00 -0800
commitbfa152fa5e4d328fe3ebf15908ee8ec20a0ce6dc (patch)
tree1695481328f884639d6237eebfa48f4c29f9ce7c
parente540eb45a5254873245fd377f2fe3afc47bd33c1 (diff)
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[PATCH] dm-multipath: fix stall on noflush suspend/resume
Allow noflush suspend/resume of device-mapper device only for the case where the device size is unchanged. Otherwise, dm-multipath devices can stall when resumed if noflush was used when suspending them, all paths have failed and queue_if_no_path is set. Explanation: 1. Something is doing fsync() on the block dev, holding inode->i_sem 2. The fsync write is blocked by all-paths-down and queue_if_no_path 3. Someone requests to suspend the dm device with noflush. Pending writes are left in queue. 4. In the middle of dm_resume(), __bind() tries to get inode->i_sem to do __set_size() and waits forever. 'noflush suspend' is a new device-mapper feature introduced in early 2.6.20. So I hope the fix being included before 2.6.20 is released. Example of reproducer: 1. Create a multipath device by dmsetup 2. Fail all paths during mkfs 3. Do dmsetup suspend --noflush and load new map with healthy paths 4. Do dmsetup resume Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com> Acked-by: Alasdair G Kergon <agk@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--drivers/md/dm.c27
1 files changed, 19 insertions, 8 deletions
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index fe7c56e1043..3668b170ea6 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1116,7 +1116,8 @@ static int __bind(struct mapped_device *md, struct dm_table *t)
if (size != get_capacity(md->disk))
memset(&md->geometry, 0, sizeof(md->geometry));
- __set_size(md, size);
+ if (md->suspended_bdev)
+ __set_size(md, size);
if (size == 0)
return 0;
@@ -1264,6 +1265,11 @@ int dm_swap_table(struct mapped_device *md, struct dm_table *table)
if (!dm_suspended(md))
goto out;
+ /* without bdev, the device size cannot be changed */
+ if (!md->suspended_bdev)
+ if (get_capacity(md->disk) != dm_table_get_size(table))
+ goto out;
+
__unbind(md);
r = __bind(md, table);
@@ -1341,11 +1347,14 @@ int dm_suspend(struct mapped_device *md, unsigned suspend_flags)
/* This does not get reverted if there's an error later. */
dm_table_presuspend_targets(map);
- md->suspended_bdev = bdget_disk(md->disk, 0);
- if (!md->suspended_bdev) {
- DMWARN("bdget failed in dm_suspend");
- r = -ENOMEM;
- goto flush_and_out;
+ /* bdget() can stall if the pending I/Os are not flushed */
+ if (!noflush) {
+ md->suspended_bdev = bdget_disk(md->disk, 0);
+ if (!md->suspended_bdev) {
+ DMWARN("bdget failed in dm_suspend");
+ r = -ENOMEM;
+ goto flush_and_out;
+ }
}
/*
@@ -1473,8 +1482,10 @@ int dm_resume(struct mapped_device *md)
unlock_fs(md);
- bdput(md->suspended_bdev);
- md->suspended_bdev = NULL;
+ if (md->suspended_bdev) {
+ bdput(md->suspended_bdev);
+ md->suspended_bdev = NULL;
+ }
clear_bit(DMF_SUSPENDED, &md->flags);