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authorMikulas Patocka <mpatocka@redhat.com>2015-02-26 11:41:28 -0500
committerMike Snitzer <snitzer@redhat.com>2015-02-27 14:53:16 -0500
commit09ee96b21456883e108c3b00597bb37ec512151b (patch)
tree76127a2e0766158b04c2b764e9e23fcd49127ccc /drivers/md/dm.c
parentb735fede8d957d9d255e9c5cf3964cfa59799637 (diff)
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@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Cc: stable@vger.kernel.org
Diffstat (limited to 'drivers/md/dm.c')
-rw-r--r--drivers/md/dm.c13
1 files changed, 13 insertions, 0 deletions
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 6e2b2e97abe9..9b641b38b857 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -2616,6 +2616,19 @@ 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;