This is backport of 09ee96b21456883e108c3b00597bb37ec512151b for 3.10 and
3.14.
commit 09ee96b21456883e108c3b00597bb37ec512151b
Author: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Date: Thu Feb 26 11:41:28 2015 -0500
dm snapshot: suspend merging snapshot when doing exception handover
The "dm snapshot: suspend origin when doing exception handover" commit
fixed a exception store handover bug associated with pending exceptions
to the "snapshot-origin" target.
However, a similar problem exists in snapshot merging. When snapshot
merging is in progress, we use the target "snapshot-merge" instead of
"snapshot-origin". Consequently, during exception store handover, we
must find the snapshot-merge target and suspend its associated
mapped_device.
To avoid lockdep warnings, the target must be suspended and resumed
without holding _origins_lock.
Introduce a dm_hold() function that grabs a reference on a
mapped_device, but unlike dm_get(), it doesn't crash if the device has
the DMF_FREEING flag set, it returns an error in this case.
In snapshot_resume() we grab the reference to the origin device using
dm_hold() while holding _origins_lock (_origins_lock guarantees that the
device won't disappear). Then we release _origins_lock, suspend the
device and grab _origins_lock again.
NOTE to stable@ people:
When backporting to kernels 3.18 and older, use dm_internal_suspend and
dm_internal_resume instead of dm_internal_suspend_fast and
dm_internal_resume_fast.
Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
drivers/md/dm-snap.c | 39 +++++++++++++++++++++++++++++++--------
drivers/md/dm.c | 13 +++++++++++++
include/linux/device-mapper.h | 1 +
3 files changed, 45 insertions(+), 8 deletions(-)
Index: linux-stable/drivers/md/dm-snap.c
===================================================================
--- linux-stable.orig/drivers/md/dm-snap.c 2015-06-02 18:34:42.000000000 +0200
+++ linux-stable/drivers/md/dm-snap.c 2015-06-02 18:36:01.000000000 +0200
@@ -1895,20 +1895,39 @@ static int snapshot_preresume(struct dm_
static void snapshot_resume(struct dm_target *ti)
{
struct dm_snapshot *s = ti->private;
- struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
+ struct dm_snapshot *snap_src = NULL, *snap_dest = NULL, *snap_merging = NULL;
struct dm_origin *o;
struct mapped_device *origin_md = NULL;
+ bool must_restart_merging = false;
down_read(&_origins_lock);
o = __lookup_dm_origin(s->origin->bdev);
if (o)
origin_md = dm_table_get_md(o->ti->table);
- if (origin_md == dm_table_get_md(ti->table))
- origin_md = NULL;
+ if (!origin_md) {
+ (void) __find_snapshots_sharing_cow(s, NULL, NULL, &snap_merging);
+ if (snap_merging)
+ origin_md = dm_table_get_md(snap_merging->ti->table);
+ }
+ if (origin_md == dm_table_get_md(ti->table))
+ origin_md = NULL;
+ if (origin_md) {
+ if (dm_hold(origin_md))
+ origin_md = NULL;
+ }
+
+ up_read(&_origins_lock);
- if (origin_md)
+ if (origin_md) {
dm_internal_suspend(origin_md);
+ if (snap_merging && test_bit(RUNNING_MERGE, &snap_merging->state_bits)) {
+ must_restart_merging = true;
+ stop_merge(snap_merging);
+ }
+ }
+
+ down_read(&_origins_lock);
(void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
if (snap_src && snap_dest) {
@@ -1919,11 +1938,15 @@ static void snapshot_resume(struct dm_ta
up_write(&snap_src->lock);
}
- if (origin_md)
- dm_internal_resume(origin_md);
-
up_read(&_origins_lock);
+ if (origin_md) {
+ if (must_restart_merging)
+ start_merge(snap_merging);
+ dm_internal_resume(origin_md);
+ dm_put(origin_md);
+ }
+
/* Now we have correct chunk size, reregister */
reregister_snapshot(s);
@@ -2356,7 +2379,7 @@ static struct target_type snapshot_targe
static struct target_type merge_target = {
.name = dm_snapshot_merge_target_name,
- .version = {1, 2, 0},
+ .version = {1, 3, 0},
.module = THIS_MODULE,
.ctr = snapshot_ctr,
.dtr = snapshot_dtr,
Index: linux-stable/drivers/md/dm.c
===================================================================
--- linux-stable.orig/drivers/md/dm.c 2015-06-02 18:34:42.000000000 +0200
+++ linux-stable/drivers/md/dm.c 2015-06-02 18:35:24.000000000 +0200
@@ -2333,6 +2333,19 @@ void dm_get(struct mapped_device *md)
BUG_ON(test_bit(DMF_FREEING, &md->flags));
}
+int dm_hold(struct mapped_device *md)
+{
+ spin_lock(&_minor_lock);
+ if (test_bit(DMF_FREEING, &md->flags)) {
+ spin_unlock(&_minor_lock);
+ return -EBUSY;
+ }
+ dm_get(md);
+ spin_unlock(&_minor_lock);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(dm_hold);
+
const char *dm_device_name(struct mapped_device *md)
{
return md->name;
Index: linux-stable/include/linux/device-mapper.h
===================================================================
--- linux-stable.orig/include/linux/device-mapper.h 2015-06-02 18:34:42.000000000 +0200
+++ linux-stable/include/linux/device-mapper.h 2015-06-02 18:35:24.000000000 +0200
@@ -373,6 +373,7 @@ int dm_create(int minor, struct mapped_d
*/
struct mapped_device *dm_get_md(dev_t dev);
void dm_get(struct mapped_device *md);
+int dm_hold(struct mapped_device *md);
void dm_put(struct mapped_device *md);
/*
--
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