In order to truly serialize reference counting and properly handle the final
dm_put, we need to use atomic_dec_and_lock, since another thread of execution
can attempt to "resurrect" a potentially dead mapped_device.
This patch replaces the _minor_lock mutex with a spinlock, and leverages
atomic_dec_and_lock to properly serialize reference counting.
Signed-off-by: Jeff Mahoney <[email protected]>
--
drivers/md/dm.c | 27 +++++++++++++--------------
1 files changed, 13 insertions(+), 14 deletions(-)
diff -ruNpX ../dontdiff linux-2.6.16-staging1/drivers/md/dm.c linux-2.6.16-staging2/drivers/md/dm.c
--- linux-2.6.16-staging1/drivers/md/dm.c 2006-04-13 16:18:19.000000000 -0400
+++ linux-2.6.16-staging2/drivers/md/dm.c 2006-04-13 16:18:19.000000000 -0400
@@ -23,6 +23,7 @@ static const char *_name = DM_NAME;
static unsigned int major = 0;
static unsigned int _major = 0;
+static DEFINE_SPINLOCK(_minor_lock);
/*
* One of these is allocated per bio.
*/
@@ -697,14 +698,13 @@ static int dm_any_congested(void *conges
/*-----------------------------------------------------------------
* An IDR is used to keep track of allocated minor numbers.
*---------------------------------------------------------------*/
-static DECLARE_MUTEX(_minor_lock);
static DEFINE_IDR(_minor_idr);
static void free_minor(unsigned int minor)
{
- down(&_minor_lock);
+ spin_lock(&_minor_lock);
idr_remove(&_minor_idr, minor);
- up(&_minor_lock);
+ spin_unlock(&_minor_lock);
}
/*
@@ -721,7 +721,7 @@ static int specific_minor(struct mapped_
if (!r)
return -ENOMEM;
- down(&_minor_lock);
+ spin_lock(&_minor_lock);
if (idr_find(&_minor_idr, minor)) {
r = -EBUSY;
@@ -740,7 +740,7 @@ static int specific_minor(struct mapped_
}
out:
- up(&_minor_lock);
+ spin_unlock(&_minor_lock);
return r;
}
@@ -753,7 +753,7 @@ static int next_free_minor(struct mapped
if (!r)
return -ENOMEM;
- down(&_minor_lock);
+ spin_lock(&_minor_lock);
r = idr_get_new(&_minor_idr, MINOR_ALLOCED, &m);
if (r) {
@@ -769,7 +769,7 @@ static int next_free_minor(struct mapped
*minor = m;
out:
- up(&_minor_lock);
+ spin_unlock(&_minor_lock);
return r;
}
@@ -839,9 +839,9 @@ static struct mapped_device *alloc_dev(u
init_waitqueue_head(&md->eventq);
/* Populate the mapping, nobody knows we exist yet */
- down(&_minor_lock);
+ spin_lock(&_minor_lock);
r = idr_replace(&_minor_idr, md, minor);
- up(&_minor_lock);
+ spin_unlock(&_minor_lock);
BUG_ON(r < 0);
return md;
@@ -964,13 +964,13 @@ static struct mapped_device *dm_find_md(
if (MAJOR(dev) != _major || minor >= (1 << MINORBITS))
return NULL;
- down(&_minor_lock);
+ spin_lock(&_minor_lock);
md = idr_find(&_minor_idr, minor);
if (md && (md == MINOR_ALLOCED || (dm_disk(md)->first_minor != minor)))
md = NULL;
- up(&_minor_lock);
+ spin_unlock(&_minor_lock);
return md;
}
@@ -1010,10 +1010,9 @@ void dm_put(struct mapped_device *md)
{
struct dm_table *map = dm_get_table(md);
- if (atomic_dec_and_test(&md->holders)) {
- down(&_minor_lock);
+ if (atomic_dec_and_lock(&md->holders, &_minor_lock)) {
idr_replace(&_minor_idr, MINOR_ALLOCED, md->disk->first_minor);
- up(&_minor_lock);
+ spin_unlock(&_minor_lock);
if (!dm_suspended(md)) {
dm_table_presuspend_targets(map);
dm_table_postsuspend_targets(map);
-
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