[PATCH] dm: change minor_lock to spinlock
While removing a device, another another thread might attempt to resurrect it.
This patch replaces the _minor_lock mutex with a spinlock and uses
atomic_dec_and_lock() to serialize reference counting in dm_put().
[akpm: too late for 2.6.17 - suitable for 2.6.17.x after it has settled]
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 6e577e7..6e65d85 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -26,6 +26,7 @@
static unsigned int major = 0;
static unsigned int _major = 0;
+static DEFINE_SPINLOCK(_minor_lock);
/*
* One of these is allocated per bio.
*/
@@ -746,14 +747,13 @@
/*-----------------------------------------------------------------
* An IDR is used to keep track of allocated minor numbers.
*---------------------------------------------------------------*/
-static DEFINE_MUTEX(_minor_lock);
static DEFINE_IDR(_minor_idr);
static void free_minor(unsigned int minor)
{
- mutex_lock(&_minor_lock);
+ spin_lock(&_minor_lock);
idr_remove(&_minor_idr, minor);
- mutex_unlock(&_minor_lock);
+ spin_unlock(&_minor_lock);
}
/*
@@ -770,7 +770,7 @@
if (!r)
return -ENOMEM;
- mutex_lock(&_minor_lock);
+ spin_lock(&_minor_lock);
if (idr_find(&_minor_idr, minor)) {
r = -EBUSY;
@@ -788,7 +788,7 @@
}
out:
- mutex_unlock(&_minor_lock);
+ spin_unlock(&_minor_lock);
return r;
}
@@ -801,7 +801,7 @@
if (!r)
return -ENOMEM;
- mutex_lock(&_minor_lock);
+ spin_lock(&_minor_lock);
r = idr_get_new(&_minor_idr, MINOR_ALLOCED, &m);
if (r) {
@@ -817,7 +817,7 @@
*minor = m;
out:
- mutex_unlock(&_minor_lock);
+ spin_unlock(&_minor_lock);
return r;
}
@@ -887,9 +887,9 @@
init_waitqueue_head(&md->eventq);
/* Populate the mapping, nobody knows we exist yet */
- mutex_lock(&_minor_lock);
+ spin_lock(&_minor_lock);
old_md = idr_replace(&_minor_idr, md, minor);
- mutex_unlock(&_minor_lock);
+ spin_unlock(&_minor_lock);
BUG_ON(old_md != MINOR_ALLOCED);
@@ -1020,13 +1020,13 @@
if (MAJOR(dev) != _major || minor >= (1 << MINORBITS))
return NULL;
- mutex_lock(&_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;
- mutex_unlock(&_minor_lock);
+ spin_unlock(&_minor_lock);
return md;
}
@@ -1060,11 +1060,10 @@
{
struct dm_table *map;
- if (atomic_dec_and_test(&md->holders)) {
+ if (atomic_dec_and_lock(&md->holders, &_minor_lock)) {
map = dm_get_table(md);
- mutex_lock(&_minor_lock);
idr_replace(&_minor_idr, MINOR_ALLOCED, dm_disk(md)->first_minor);
- mutex_unlock(&_minor_lock);
+ spin_unlock(&_minor_lock);
if (!dm_suspended(md)) {
dm_table_presuspend_targets(map);
dm_table_postsuspend_targets(map);