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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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