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Commit f32c10b0 authored by Jeff Mahoney's avatar Jeff Mahoney Committed by Linus Torvalds
Browse files

[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: default avatarJeff Mahoney <jeffm@suse.com>
Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
Cc: <stable@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 62f75c2f

drivers/md/dm.c

+13 −14
Original line number Diff line number Diff line
@@ -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 *congested_data, int bdi_bits) 
/*-----------------------------------------------------------------

 * 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_device *md, unsigned int minor) 
	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_device *md, unsigned int minor) 
	}



out:

	mutex_unlock(&_minor_lock);

	spin_unlock(&_minor_lock);

	return r;

}
@@ -801,7 +801,7 @@ static int next_free_minor(struct mapped_device *md, unsigned int *minor) 
	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_device *md, unsigned int *minor) 
	*minor = m;



out:

	mutex_unlock(&_minor_lock);

	spin_unlock(&_minor_lock);

	return r;

}
@@ -887,9 +887,9 @@ static struct mapped_device *alloc_dev(unsigned int minor, int persistent) 
	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(dev_t dev) 
	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);