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Commit ba61fdd1 authored by Jeff Mahoney's avatar Jeff Mahoney Committed by Linus Torvalds
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[PATCH] dm: fix idr minor allocation 



One part of the system can attempt to use a mapped device before another has
finished initialising it or while it is being freed.

This patch introduces a place holder value, MINOR_ALLOCED, to mark the minor
as allocated but in a state where it can't be used, such as mid-allocation or
mid-free.  At the end of the initialization, it replaces the place holder with
the pointer to the mapped_device, making it available to the rest of the dm
subsystem.

[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 5806f07c

drivers/md/dm.c

+16 −3
Original line number Diff line number Diff line
@@ -54,6 +54,8 @@ union map_info *dm_get_mapinfo(struct bio *bio) 
        return NULL;

}



#define MINOR_ALLOCED ((void *)-1)



/*

 * Bits for the md->flags field.

 */
@@ -777,7 +779,7 @@ static int specific_minor(struct mapped_device *md, unsigned int minor) 
		goto out;

	}



	r = idr_get_new_above(&_minor_idr, md, minor, &m);

	r = idr_get_new_above(&_minor_idr, MINOR_ALLOCED, minor, &m);

	if (r) {

		goto out;

	}
@@ -806,7 +808,7 @@ static int next_free_minor(struct mapped_device *md, unsigned int *minor) 
		goto out;

	}



	r = idr_get_new(&_minor_idr, md, &m);

	r = idr_get_new(&_minor_idr, MINOR_ALLOCED, &m);

	if (r) {

		goto out;

	}
@@ -833,6 +835,7 @@ static struct mapped_device *alloc_dev(unsigned int minor, int persistent) 
{

	int r;

	struct mapped_device *md = kmalloc(sizeof(*md), GFP_KERNEL);

	void *old_md;



	if (!md) {

		DMWARN("unable to allocate device, out of memory.");
@@ -888,6 +891,13 @@ static struct mapped_device *alloc_dev(unsigned int minor, int persistent) 
	init_waitqueue_head(&md->wait);

	init_waitqueue_head(&md->eventq);



	/* Populate the mapping, nobody knows we exist yet */

	mutex_lock(&_minor_lock);

	old_md = idr_replace(&_minor_idr, md, minor);

	mutex_unlock(&_minor_lock);



	BUG_ON(old_md != MINOR_ALLOCED);



	return md;



 bad4:
@@ -1018,7 +1028,7 @@ static struct mapped_device *dm_find_md(dev_t dev) 
	mutex_lock(&_minor_lock);



	md = idr_find(&_minor_idr, minor);

	if (!md || (dm_disk(md)->first_minor != minor))

	if (md && (md == MINOR_ALLOCED || (dm_disk(md)->first_minor != minor)))

		md = NULL;



	mutex_unlock(&_minor_lock);
@@ -1057,6 +1067,9 @@ void dm_put(struct mapped_device *md) 


	if (atomic_dec_and_test(&md->holders)) {

		map = dm_get_table(md);

		mutex_lock(&_minor_lock);

		idr_replace(&_minor_idr, MINOR_ALLOCED, dm_disk(md)->first_minor);

		mutex_unlock(&_minor_lock);

		if (!dm_suspended(md)) {

			dm_table_presuspend_targets(map);

			dm_table_postsuspend_targets(map);