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dm snapshot: lock snapshot while supplying status 

This patch locks the snapshot when returning status.  It fixes a race
when it could return an invalid number of free chunks if someone
was simultaneously modifying 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 2009-10-16 23:18:16 +01:00 committed by Alasdair G Kergon
parent 0e8c4e4e3e
commit 4c6fff445d
1 changed files with 4 additions and 0 deletions
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4
drivers/md/dm-snap.c
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@ -1152,6 +1152,8 @@ 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:
if (!snap->valid) if (!snap->valid)
@ -1183,6 +1185,8 @@ static int snapshot_status(struct dm_target *ti, status_type_t type,
break; break;
} }
up_write(&snap->lock);
return 0; return 0;
} }