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Subject[patch 11/37] dm: change minor_lock to spinlock
-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Jeff Mahoney <jeffm@suse.com>

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>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---

drivers/md/dm.c | 27 +++++++++++++--------------
1 file changed, 13 insertions(+), 14 deletions(-)

--- linux-2.6.17.11.orig/drivers/md/dm.c
+++ linux-2.6.17.11/drivers/md/dm.c
@@ -26,6 +26,7 @@ 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.
*/
@@ -746,14 +747,13 @@ static int dm_any_congested(void *conges
/*-----------------------------------------------------------------
* 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 @@ static int specific_minor(struct mapped_
if (!r)
return -ENOMEM;

- mutex_lock(&_minor_lock);
+ spin_lock(&_minor_lock);

if (idr_find(&_minor_idr, minor)) {
r = -EBUSY;
@@ -788,7 +788,7 @@ static int specific_minor(struct mapped_
}

out:
- mutex_unlock(&_minor_lock);
+ spin_unlock(&_minor_lock);
return r;
}

@@ -801,7 +801,7 @@ static int next_free_minor(struct mapped
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 @@ static int next_free_minor(struct mapped
*minor = m;

out:
- mutex_unlock(&_minor_lock);
+ spin_unlock(&_minor_lock);
return r;
}

@@ -887,9 +887,9 @@ static struct mapped_device *alloc_dev(u
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 @@ static struct mapped_device *dm_find_md(
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 @@ void dm_put(struct mapped_device *md)
{
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);
--
-
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