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dm snapshot: only take lock for statustype info not table

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Take snapshot lock only for STATUSTYPE_INFO, not STATUSTYPE_TABLE.

Commit 4c6fff445d
(dm-snapshot-lock-snapshot-while-supplying-status.patch)
introduced this use of the lock, but userspace applications using
libdevmapper have been found to request STATUSTYPE_TABLE while the device
is suspended and the lock is already held, leading to deadlock.  Since
the lock is not necessary in this case, don't try to take it.

Cc: stable@kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
This commit is contained in:
Mikulas Patocka 2009-12-10 23:51:53 +00:00 • committed by Alasdair G Kergon
parent d2bb7df8ca
commit 94e76572b5
1 changed files with 6 additions and 4 deletions
Download patch file Download diff file Expand all files Collapse all files

10
drivers/md/dm-snap.c
View file

@ -1152,10 +1152,11 @@ static int snapshot_status(struct dm_target *ti, status_type_t type,
unsigned sz = 0; unsigned sz = 0;
struct dm_snapshot *snap = ti->private; struct dm_snapshot *snap = ti->private;
down_write(&snap->lock);
switch (type) { switch (type) {
case STATUSTYPE_INFO: case STATUSTYPE_INFO:
down_write(&snap->lock);
if (!snap->valid) if (!snap->valid)
DMEMIT("Invalid"); DMEMIT("Invalid");
else { else {
@ -1171,6 +1172,9 @@ static int snapshot_status(struct dm_target *ti, status_type_t type,
else else
DMEMIT("Unknown"); DMEMIT("Unknown");
} }
up_write(&snap->lock);
break; break;
case STATUSTYPE_TABLE: case STATUSTYPE_TABLE:
@ -1185,8 +1189,6 @@ static int snapshot_status(struct dm_target *ti, status_type_t type,
break; break;
} }
up_write(&snap->lock);
return 0; return 0;
} }