From: Andrew Morton <akpm@osdl.org>

BUG: using smp_processor_id() in preemptible [00000001] code: khelper/972
caller is drive_stat_acct+0x37/0x5e

Call Trace:
 [<ffffffff80343f8d>] debug_smp_processor_id+0xb1/0xc4
 [<ffffffff80331eac>] drive_stat_acct+0x37/0x5e
 [<ffffffff80334d49>] bio_attempt_back_merge+0x87/0x91
 [<ffffffff803351c9>] __make_request+0xb9/0x2ed
 [<ffffffff803329cc>] generic_make_request+0x1e9/0x222
 [<ffffffff80333a9c>] submit_bio+0xfb/0x108
 [<ffffffff802a1276>] mpage_bio_submit+0x22/0x26
 [<ffffffff802a1836>] do_mpage_readpage+0x44a/0x4e2
 [<ffffffff8033f85b>] radix_tree_insert+0x69/0x1dc
 [<ffffffff80264d81>] __inc_zone_state+0x11/0x6d
 ...

<sadly points at Documentation/SubmitChecklist>

Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---

 block/ll_rw_blk.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff -puN block/ll_rw_blk.c~git-block-atomicity-fix block/ll_rw_blk.c
--- a/block/ll_rw_blk.c~git-block-atomicity-fix
+++ a/block/ll_rw_blk.c
@@ -2577,7 +2577,7 @@ static void drive_stat_acct(struct reque
 		return;
 
 	if (!new_io) {
-		__disk_stat_inc(rq->rq_disk, merges[rw]);
+		disk_stat_inc(rq->rq_disk, merges[rw]);
 	} else {
 		disk_round_stats(rq->rq_disk);
 		rq->rq_disk->in_flight++;
_