Always keep the reference to structure block_device. Reference to block_device is obtained with function bdget_disk (and is released with bdput. bdget_disk was called while the device was being suspended, in dm_suspend() --- however at this point, there could be another devices already suspended. bdget_disk can wait for IO and allocate memory and this could result in waiting for already suspended device, resulting in deadlock. It caused bug https://bugzilla.redhat.com/show_bug.cgi?id=179786 This patch changes the code so that it gets the reference to struct block_device when struct mapped_device is allocated and initialized in (alloc_dev) and drops the reference when it is destroyed in free_dev. Thus, there is no call to bdget_disk, while any device is suspended. Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx> --- drivers/md/dm.c | 37 +++++++++---------------------------- 1 file changed, 9 insertions(+), 28 deletions(-) Index: linux-2.6.30-rc2-devel/drivers/md/dm.c =================================================================== --- linux-2.6.30-rc2-devel.orig/drivers/md/dm.c 2009-04-15 16:24:19.000000000 +0200 +++ linux-2.6.30-rc2-devel/drivers/md/dm.c 2009-04-15 16:24:25.000000000 +0200 @@ -1183,6 +1183,10 @@ static struct mapped_device *alloc_dev(i if (!md->wq) goto bad_thread; + md->bdev = bdget_disk(md->disk, 0); + if (!md->bdev) + goto bad_bdev; + /* Populate the mapping, nobody knows we exist yet */ spin_lock(&_minor_lock); old_md = idr_replace(&_minor_idr, md, minor); @@ -1192,6 +1196,8 @@ static struct mapped_device *alloc_dev(i return md; +bad_bdev: + destroy_workqueue(md->wq); bad_thread: put_disk(md->disk); bad_disk: @@ -1217,10 +1223,8 @@ static void free_dev(struct mapped_devic { int minor = MINOR(disk_devt(md->disk)); - if (md->bdev) { - unlock_fs(md); - bdput(md->bdev); - } + unlock_fs(md); + bdput(md->bdev); destroy_workqueue(md->wq); mempool_destroy(md->tio_pool); mempool_destroy(md->io_pool); @@ -1280,8 +1284,7 @@ static int __bind(struct mapped_device * if (size != get_capacity(md->disk)) memset(&md->geometry, 0, sizeof(md->geometry)); - if (md->bdev) - __set_size(md, size); + __set_size(md, size); if (!size) { dm_table_destroy(t); @@ -1523,11 +1526,6 @@ int dm_swap_table(struct mapped_device * if (!dm_suspended(md)) goto out; - /* without bdev, the device size cannot be changed */ - if (!md->bdev) - if (get_capacity(md->disk) != dm_table_get_size(table)) - goto out; - __unbind(md); r = __bind(md, table); @@ -1606,13 +1604,6 @@ int dm_suspend(struct mapped_device *md, /* bdget() can stall if the pending I/Os are not flushed */ if (!noflush) { - md->bdev = bdget_disk(md->disk, 0); - if (!md->bdev) { - DMWARN("bdget failed in dm_suspend"); - r = -ENOMEM; - goto out; - } - /* * Flush I/O to the device. noflush supersedes do_lockfs, * because lock_fs() needs to flush I/Os. @@ -1678,11 +1669,6 @@ int dm_suspend(struct mapped_device *md, set_bit(DMF_SUSPENDED, &md->flags); out: - if (r && md->bdev) { - bdput(md->bdev); - md->bdev = NULL; - } - dm_table_put(map); out_unlock: @@ -1711,11 +1697,6 @@ int dm_resume(struct mapped_device *md) unlock_fs(md); - if (md->bdev) { - bdput(md->bdev); - md->bdev = NULL; - } - clear_bit(DMF_SUSPENDED, &md->flags); dm_table_unplug_all(map); -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
