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Subject[patch 12/37] dm: add DMF_FREEING
-stable review patch.  If anyone has any objections, please let us know.

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

From: Jeff Mahoney <jeffm@suse.com>

There is a chicken and egg problem between the block layer and dm in which the
gendisk associated with a mapping keeps a reference-less pointer to the
mapped_device.

This patch uses a new flag DMF_FREEING to indicate when the mapped_device is
no longer valid. This is checked to prevent any attempt to open the device
from succeeding while the device is being destroyed.

[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 | 32 ++++++++++++++++++++++++++++++--
1 file changed, 30 insertions(+), 2 deletions(-)

--- linux-2.6.17.11.orig/drivers/md/dm.c
+++ linux-2.6.17.11/drivers/md/dm.c
@@ -63,6 +63,7 @@ union map_info *dm_get_mapinfo(struct bi
#define DMF_BLOCK_IO 0
#define DMF_SUSPENDED 1
#define DMF_FROZEN 2
+#define DMF_FREEING 3

struct mapped_device {
struct rw_semaphore io_lock;
@@ -221,9 +222,23 @@ static int dm_blk_open(struct inode *ino
{
struct mapped_device *md;

+ spin_lock(&_minor_lock);
+
md = inode->i_bdev->bd_disk->private_data;
+ if (!md)
+ goto out;
+
+ if (test_bit(DMF_FREEING, &md->flags)) {
+ md = NULL;
+ goto out;
+ }
+
dm_get(md);
- return 0;
+
+out:
+ spin_unlock(&_minor_lock);
+
+ return md ? 0 : -ENXIO;
}

static int dm_blk_close(struct inode *inode, struct file *file)
@@ -919,6 +934,11 @@ static void free_dev(struct mapped_devic
mempool_destroy(md->io_pool);
del_gendisk(md->disk);
free_minor(minor);
+
+ spin_lock(&_minor_lock);
+ md->disk->private_data = NULL;
+ spin_unlock(&_minor_lock);
+
put_disk(md->disk);
blk_cleanup_queue(md->queue);
kfree(md);
@@ -1023,9 +1043,14 @@ static struct mapped_device *dm_find_md(
spin_lock(&_minor_lock);

md = idr_find(&_minor_idr, minor);
- if (md && (md == MINOR_ALLOCED || (dm_disk(md)->first_minor != minor)))
+ if (md && (md == MINOR_ALLOCED ||
+ (dm_disk(md)->first_minor != minor) ||
+ test_bit(DMF_FREEING, &md->flags))) {
md = NULL;
+ goto out;
+ }

+out:
spin_unlock(&_minor_lock);

return md;
@@ -1060,9 +1085,12 @@ void dm_put(struct mapped_device *md)
{
struct dm_table *map;

+ BUG_ON(test_bit(DMF_FREEING, &md->flags));
+
if (atomic_dec_and_lock(&md->holders, &_minor_lock)) {
map = dm_get_table(md);
idr_replace(&_minor_idr, MINOR_ALLOCED, dm_disk(md)->first_minor);
+ set_bit(DMF_FREEING, &md->flags);
spin_unlock(&_minor_lock);
if (!dm_suspended(md)) {
dm_table_presuspend_targets(map);
--
-
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