This patch is trying to fix a kernel crash bug. When kernel boots on a HP large system, it crashes. The reason is when blk_rq_init is called, the second parameter rq , which is a member as q->flush_rq, is NULL. Kernel does not allocate space for it. This fix adds an alloc for flush_rq member when request_queue is created in struct mapped_device *alloc_dev(int minor); Bug Details: Error message: [ 62.931942] BUG: unable to handle kernel NULL pointer dereference at (null) [ 62.931949] IP: [<ffffffff812b3f30>] blk_rq_init+0x40/0x160^M [ 62.931949] PGD 0 ^M [ 62.931951] Oops: 0002 [#1] SMP [ 62.932019] Call Trace: [ 62.932025] [<ffffffff812bc5b8>] blk_flush_complete_seq+0x2d8/0x300 [ 62.932027] [<ffffffff812bca55>] blk_insert_flush+0x1e5/0x250 [ 62.932029] [<ffffffff812b3038>] __elv_add_request+0x1d8/0x2d0 [ 62.932031] [<ffffffff812ba630>] blk_flush_plug_list+0x140/0x230 [ 62.932033] [<ffffffff812baab4>] blk_finish_plug+0x14/0x40 [ 62.932041] [<ffffffffa0311e0c>] _xfs_buf_ioapply+0x2fc/0x3d0 [xfs] [ 62.932053] [<ffffffffa036e63f>] ? xlog_bdstrat+0x1f/0x50 [xfs] [ 62.932061] [<ffffffffa0313716>] xfs_buf_iorequest+0x46/0x90 [xfs] [ 62.932071] [<ffffffffa036e63f>] xlog_bdstrat+0x1f/0x50 [xfs] [ 62.932080] [<ffffffffa0370385>] xlog_sync+0x265/0x450 [xfs] [ 62.932090] [<ffffffffa0370602>] xlog_state_release_iclog+0x92/0xb0 [xfs] [ 62.932099] [<ffffffffa03713ba>] _xfs_log_force+0x15a/0x290 [xfs] [ 62.932108] [<ffffffffa0371516>] xfs_log_force+0x26/0x80 [xfs] [ 62.932117] [<ffffffffa0371594>] xfs_log_worker+0x24/0x50 [xfs] [ 62.932122] [<ffffffff8108ce8b>] process_one_work+0x17b/0x460 [ 62.932125] [<ffffffff8108dc5b>] worker_thread+0x11b/0x400 [ 62.932126] [<ffffffff8108db40>] ? rescuer_thread+0x400/0x400 [ 62.932130] [<ffffffff81094ca1>] kthread+0xe1/0x100 [ 62.932133] [<ffffffff81094bc0>] ? kthread_create_on_node+0x1a0/0x1a0 [ 62.932140] [<ffffffff8162ae3c>] ret_from_fork+0x7c/0xb0 [ 62.932141] [<ffffffff81094bc0>] ? kthread_create_on_node+0x1a0/0x1a0 Signed-off-by: Li, Zhen-Hua <zhen-hual@xxxxxx> --- drivers/md/dm.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/md/dm.c b/drivers/md/dm.c index 455e649..9ff6df6 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -1893,6 +1893,10 @@ static struct mapped_device *alloc_dev(int minor) if (!md->queue) goto bad_queue; + md->queue->flush_rq = kzalloc(sizeof(struct request), GFP_KERNEL); + if (!md->queue->flush_rq) + goto bad_disk; + dm_init_md_queue(md); md->disk = alloc_disk(1); -- 2.0.0-rc0 -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
