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authorAlasdair G Kergon <agk@redhat.com>2005-07-28 21:16:00 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2005-07-28 21:46:03 -0700
commit2ca3310e78912a527d7d2c62c01da7cbf7346b8d (patch)
tree3eb83a509487d5b85d346630e9d700d73d28e39e
parent4e90188be4a56f37fbb4ffb5b58745683526dcb9 (diff)
[PATCH] device-mapper: fix md->lock deadlocks in core
This patch is an attempt to fix deadlocks discovered in the core dm. The problems boil down to md->lock having to be held in too many places, so I've split it into two: md->suspend_lock and md->io_lock. suspend_lock is now held throughout dm_suspended() as well as dm_resume() and dm_swap_table() so that these functions cannot run concurrently: there's no requirement for that and it added complexity. DMF_FS_LOCKED becomes redundant: DMF_SUSPENDED provides adequate protection. 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.c138
1 files changed, 60 insertions, 78 deletions
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 88f1f27526c..d487d9deb98 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -55,10 +55,10 @@ union map_info *dm_get_mapinfo(struct bio *bio)
*/
#define DMF_BLOCK_IO 0
#define DMF_SUSPENDED 1
-#define DMF_FS_LOCKED 2
struct mapped_device {
- struct rw_semaphore lock;
+ struct rw_semaphore io_lock;
+ struct semaphore suspend_lock;
rwlock_t map_lock;
atomic_t holders;
@@ -248,16 +248,16 @@ static inline void free_tio(struct mapped_device *md, struct target_io *tio)
*/
static int queue_io(struct mapped_device *md, struct bio *bio)
{
- down_write(&md->lock);
+ down_write(&md->io_lock);
if (!test_bit(DMF_BLOCK_IO, &md->flags)) {
- up_write(&md->lock);
+ up_write(&md->io_lock);
return 1;
}
bio_list_add(&md->deferred, bio);
- up_write(&md->lock);
+ up_write(&md->io_lock);
return 0; /* deferred successfully */
}
@@ -568,14 +568,14 @@ static int dm_request(request_queue_t *q, struct bio *bio)
int r;
struct mapped_device *md = q->queuedata;
- down_read(&md->lock);
+ down_read(&md->io_lock);
/*
* If we're suspended we have to queue
* this io for later.
*/
while (test_bit(DMF_BLOCK_IO, &md->flags)) {
- up_read(&md->lock);
+ up_read(&md->io_lock);
if (bio_rw(bio) == READA) {
bio_io_error(bio, bio->bi_size);
@@ -594,11 +594,11 @@ static int dm_request(request_queue_t *q, struct bio *bio)
* We're in a while loop, because someone could suspend
* before we get to the following read lock.
*/
- down_read(&md->lock);
+ down_read(&md->io_lock);
}
__split_bio(md, bio);
- up_read(&md->lock);
+ up_read(&md->io_lock);
return 0;
}
@@ -747,7 +747,8 @@ static struct mapped_device *alloc_dev(unsigned int minor, int persistent)
goto bad1;
memset(md, 0, sizeof(*md));
- init_rwsem(&md->lock);
+ init_rwsem(&md->io_lock);
+ init_MUTEX(&md->suspend_lock);
rwlock_init(&md->map_lock);
atomic_set(&md->holders, 1);
atomic_set(&md->event_nr, 0);
@@ -844,13 +845,14 @@ static int __bind(struct mapped_device *md, struct dm_table *t)
if (size == 0)
return 0;
+ dm_table_get(t);
+ dm_table_event_callback(t, event_callback, md);
+
write_lock(&md->map_lock);
md->map = t;
+ dm_table_set_restrictions(t, q);
write_unlock(&md->map_lock);
- dm_table_get(t);
- dm_table_event_callback(t, event_callback, md);
- dm_table_set_restrictions(t, q);
return 0;
}
@@ -963,7 +965,7 @@ int dm_swap_table(struct mapped_device *md, struct dm_table *table)
{
int r = -EINVAL;
- down_write(&md->lock);
+ down(&md->suspend_lock);
/* device must be suspended */
if (!dm_suspended(md))
@@ -973,7 +975,7 @@ int dm_swap_table(struct mapped_device *md, struct dm_table *table)
r = __bind(md, table);
out:
- up_write(&md->lock);
+ up(&md->suspend_lock);
return r;
}
@@ -981,16 +983,13 @@ out:
* Functions to lock and unlock any filesystem running on the
* device.
*/
-static int __lock_fs(struct mapped_device *md)
+static int lock_fs(struct mapped_device *md)
{
int r = -ENOMEM;
- if (test_and_set_bit(DMF_FS_LOCKED, &md->flags))
- return 0;
-
md->frozen_bdev = bdget_disk(md->disk, 0);
if (!md->frozen_bdev) {
- DMWARN("bdget failed in __lock_fs");
+ DMWARN("bdget failed in lock_fs");
goto out;
}
@@ -1004,7 +1003,7 @@ static int __lock_fs(struct mapped_device *md)
/* don't bdput right now, we don't want the bdev
* to go away while it is locked. We'll bdput
- * in __unlock_fs
+ * in unlock_fs
*/
return 0;
@@ -1013,15 +1012,11 @@ out_bdput:
md->frozen_sb = NULL;
md->frozen_bdev = NULL;
out:
- clear_bit(DMF_FS_LOCKED, &md->flags);
return r;
}
-static void __unlock_fs(struct mapped_device *md)
+static void unlock_fs(struct mapped_device *md)
{
- if (!test_and_clear_bit(DMF_FS_LOCKED, &md->flags))
- return;
-
thaw_bdev(md->frozen_bdev, md->frozen_sb);
bdput(md->frozen_bdev);
@@ -1038,13 +1033,14 @@ static void __unlock_fs(struct mapped_device *md)
*/
int dm_suspend(struct mapped_device *md)
{
- struct dm_table *map;
+ struct dm_table *map = NULL;
DECLARE_WAITQUEUE(wait, current);
int r = -EINVAL;
- down_read(&md->lock);
- if (test_bit(DMF_BLOCK_IO, &md->flags))
- goto out_read_unlock;
+ down(&md->suspend_lock);
+
+ if (dm_suspended(md))
+ goto out;
map = dm_get_table(md);
@@ -1052,36 +1048,22 @@ int dm_suspend(struct mapped_device *md)
dm_table_presuspend_targets(map);
/* Flush I/O to the device. */
- r = __lock_fs(md);
- if (r) {
- dm_table_put(map);
- goto out_read_unlock;
- }
-
- up_read(&md->lock);
+ r = lock_fs(md);
+ if (r)
+ goto out;
/*
* First we set the BLOCK_IO flag so no more ios will be mapped.
- *
- * If the flag is already set we know another thread is trying to
- * suspend as well, so we leave the fs locked for this thread.
*/
- r = -EINVAL;
- down_write(&md->lock);
- if (test_and_set_bit(DMF_BLOCK_IO, &md->flags)) {
- if (map)
- dm_table_put(map);
- goto out_write_unlock;
- }
+ down_write(&md->io_lock);
+ set_bit(DMF_BLOCK_IO, &md->flags);
add_wait_queue(&md->wait, &wait);
- up_write(&md->lock);
+ up_write(&md->io_lock);
/* unplug */
- if (map) {
+ if (map)
dm_table_unplug_all(map);
- dm_table_put(map);
- }
/*
* Then we wait for the already mapped ios to
@@ -1097,32 +1079,28 @@ int dm_suspend(struct mapped_device *md)
}
set_current_state(TASK_RUNNING);
- down_write(&md->lock);
+ down_write(&md->io_lock);
remove_wait_queue(&md->wait, &wait);
/* were we interrupted ? */
r = -EINTR;
- if (atomic_read(&md->pending))
- goto out_unfreeze;
-
- set_bit(DMF_SUSPENDED, &md->flags);
+ if (atomic_read(&md->pending)) {
+ up_write(&md->io_lock);
+ unlock_fs(md);
+ clear_bit(DMF_BLOCK_IO, &md->flags);
+ goto out;
+ }
+ up_write(&md->io_lock);
- map = dm_get_table(md);
dm_table_postsuspend_targets(map);
- dm_table_put(map);
- up_write(&md->lock);
- return 0;
+ set_bit(DMF_SUSPENDED, &md->flags);
-out_unfreeze:
- __unlock_fs(md);
- clear_bit(DMF_BLOCK_IO, &md->flags);
-out_write_unlock:
- up_write(&md->lock);
- return r;
+ r = 0;
-out_read_unlock:
- up_read(&md->lock);
+out:
+ dm_table_put(map);
+ up(&md->suspend_lock);
return r;
}
@@ -1132,31 +1110,35 @@ int dm_resume(struct mapped_device *md)
struct bio *def;
struct dm_table *map = NULL;
- down_write(&md->lock);
- if (!dm_suspended(md)) {
- up_write(&md->lock);
+ down(&md->suspend_lock);
+ if (!dm_suspended(md))
goto out;
- }
map = dm_get_table(md);
- if (!map || !dm_table_get_size(map)) {
- up_write(&md->lock);
+ if (!map || !dm_table_get_size(map))
goto out;
- }
dm_table_resume_targets(map);
- clear_bit(DMF_SUSPENDED, &md->flags);
+
+ down_write(&md->io_lock);
clear_bit(DMF_BLOCK_IO, &md->flags);
def = bio_list_get(&md->deferred);
__flush_deferred_io(md, def);
- up_write(&md->lock);
- __unlock_fs(md);
+ up_write(&md->io_lock);
+
+ unlock_fs(md);
+
+ clear_bit(DMF_SUSPENDED, &md->flags);
+
dm_table_unplug_all(map);
r = 0;
+
out:
dm_table_put(map);
+ up(&md->suspend_lock);
+
return r;
}