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Subject[patch 09/37] dm: fix idr minor allocation
-stable review patch.  If anyone has any objections, please let us know.

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

From: Jeff Mahoney <jeffm@suse.com>

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: 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 | 19 ++++++++++++++++---
1 file changed, 16 insertions(+), 3 deletions(-)

--- linux-2.6.17.11.orig/drivers/md/dm.c
+++ linux-2.6.17.11/drivers/md/dm.c
@@ -54,6 +54,8 @@ union map_info *dm_get_mapinfo(struct bi
return NULL;
}

+#define MINOR_ALLOCED ((void *)-1)
+
/*
* Bits for the md->flags field.
*/
@@ -777,7 +779,7 @@ static int specific_minor(struct mapped_
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
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(u
{
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(u
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(
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);
--
-
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