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authorAlasdair G Kergon <agk@redhat.com>2005-07-12 15:53:03 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2005-07-12 16:19:10 -0700
commit436d41087d047b61f8ab0604dc74fff3240a8933 (patch)
tree46bab3a0cf02a7514b4faa5470a76326e6f8bc72
parenta044d016896d2717694003f00d31a98194077511 (diff)
downloadlinux-2.6.34-ux500-436d41087d047b61f8ab0604dc74fff3240a8933.tar.gz
[PATCH] device-mapper multipath: Avoid possible suspension deadlock
To avoid deadlock when suspending a multipath device after all its paths have failed, stop queueing any I/O that is about to fail *before* calling freeze_bdev instead of after. Instead of setting a multipath 'suspended' flag which would have to be reset if an error occurs during the process, save the previous queueing state and leave userspace to restore if it wishes. Signed-off-by: Alasdair G Kergon <agk@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--drivers/md/dm-mpath.c25
-rw-r--r--drivers/md/dm.c12
2 files changed, 20 insertions, 17 deletions
diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index fa72f015320..98da8eee2d2 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -72,7 +72,7 @@ struct multipath {
unsigned queue_io; /* Must we queue all I/O? */
unsigned queue_if_no_path; /* Queue I/O if last path fails? */
- unsigned suspended; /* Has dm core suspended our I/O? */
+ unsigned saved_queue_if_no_path;/* Saved state during suspension */
struct work_struct process_queued_ios;
struct bio_list queued_ios;
@@ -304,7 +304,7 @@ static int map_io(struct multipath *m, struct bio *bio, struct mpath_io *mpio,
m->queue_size--;
if ((pgpath && m->queue_io) ||
- (!pgpath && m->queue_if_no_path && !m->suspended)) {
+ (!pgpath && m->queue_if_no_path)) {
/* Queue for the daemon to resubmit */
bio_list_add(&m->queued_ios, bio);
m->queue_size++;
@@ -333,6 +333,7 @@ static int queue_if_no_path(struct multipath *m, unsigned queue_if_no_path)
spin_lock_irqsave(&m->lock, flags);
+ m->saved_queue_if_no_path = m->queue_if_no_path;
m->queue_if_no_path = queue_if_no_path;
if (!m->queue_if_no_path)
queue_work(kmultipathd, &m->process_queued_ios);
@@ -391,7 +392,7 @@ static void process_queued_ios(void *data)
pgpath = m->current_pgpath;
if ((pgpath && m->queue_io) ||
- (!pgpath && m->queue_if_no_path && !m->suspended))
+ (!pgpath && m->queue_if_no_path))
must_queue = 1;
init_required = m->pg_init_required;
@@ -998,7 +999,7 @@ static int do_end_io(struct multipath *m, struct bio *bio,
spin_lock(&m->lock);
if (!m->nr_valid_paths) {
- if (!m->queue_if_no_path || m->suspended) {
+ if (!m->queue_if_no_path) {
spin_unlock(&m->lock);
return -EIO;
} else {
@@ -1059,27 +1060,27 @@ static int multipath_end_io(struct dm_target *ti, struct bio *bio,
/*
* Suspend can't complete until all the I/O is processed so if
- * the last path failed we will now error any queued I/O.
+ * the last path fails we must error any remaining I/O.
+ * Note that if the freeze_bdev fails while suspending, the
+ * queue_if_no_path state is lost - userspace should reset it.
*/
static void multipath_presuspend(struct dm_target *ti)
{
struct multipath *m = (struct multipath *) ti->private;
- unsigned long flags;
- spin_lock_irqsave(&m->lock, flags);
- m->suspended = 1;
- if (m->queue_if_no_path)
- queue_work(kmultipathd, &m->process_queued_ios);
- spin_unlock_irqrestore(&m->lock, flags);
+ queue_if_no_path(m, 0);
}
+/*
+ * Restore the queue_if_no_path setting.
+ */
static void multipath_resume(struct dm_target *ti)
{
struct multipath *m = (struct multipath *) ti->private;
unsigned long flags;
spin_lock_irqsave(&m->lock, flags);
- m->suspended = 0;
+ m->queue_if_no_path = m->saved_queue_if_no_path;
spin_unlock_irqrestore(&m->lock, flags);
}
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 5d40555b42b..bb3ad79c14d 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1055,14 +1055,17 @@ int dm_suspend(struct mapped_device *md)
if (test_bit(DMF_BLOCK_IO, &md->flags))
goto out_read_unlock;
- error = __lock_fs(md);
- if (error)
- goto out_read_unlock;
-
map = dm_get_table(md);
if (map)
+ /* This does not get reverted if there's an error later. */
dm_table_presuspend_targets(map);
+ error = __lock_fs(md);
+ if (error) {
+ dm_table_put(map);
+ goto out_read_unlock;
+ }
+
up_read(&md->lock);
/*
@@ -1121,7 +1124,6 @@ int dm_suspend(struct mapped_device *md)
return 0;
out_unfreeze:
- /* FIXME Undo dm_table_presuspend_targets */
__unlock_fs(md);
clear_bit(DMF_BLOCK_IO, &md->flags);
out_write_unlock: