Commit 76fed014 authored by Xiao Ni's avatar Xiao Ni Committed by Song Liu
Browse files

md: account io_acct_set usage with active_io 



io_acct_set was enabled for raid0/raid5 io accounting. bios that contain
md_io_acct are allocated in the i/o path. There isn't a good method to
monitor if these bios are all finished and freed. In the takeover process,
io_acct_set (which is used for bios with md_io_acct) need to be freed.
However, if some bios finish after io_acct_set is freed, it may trigger
the following panic:

[ 6973.767999] RIP: 0010:mempool_free+0x52/0x80
[ 6973.786098] Call Trace:
[ 6973.786549]  md_end_io_acct+0x31/0x40
[ 6973.787227]  blk_update_request+0x224/0x380
[ 6973.787994]  blk_mq_end_request+0x1a/0x130
[ 6973.788739]  blk_complete_reqs+0x35/0x50
[ 6973.789456]  __do_softirq+0xd7/0x2c8
[ 6973.790114]  ? sort_range+0x20/0x20
[ 6973.790763]  run_ksoftirqd+0x2a/0x40
[ 6973.791400]  smpboot_thread_fn+0xb5/0x150
[ 6973.792114]  kthread+0x10b/0x130
[ 6973.792724]  ? set_kthread_struct+0x50/0x50
[ 6973.793491]  ret_from_fork+0x1f/0x40

Fix this by increasing and decreasing active_io for each bio with
md_io_acct so that mddev_suspend() will wait until all bios from
io_acct_set finish before freeing io_acct_set.

Reported-by: default avatarFine Fan <ffan@redhat.com>
Signed-off-by: default avatarXiao Ni <xni@redhat.com>
Signed-off-by: default avatarSong Liu <song@kernel.org>
parent 0abe39de

drivers/md/md.c

+6 −0
Original line number Diff line number Diff line
@@ -8628,12 +8628,15 @@ static void md_end_io_acct(struct bio *bio) 
{

	struct md_io_acct *md_io_acct = bio->bi_private;

	struct bio *orig_bio = md_io_acct->orig_bio;

	struct mddev *mddev = md_io_acct->mddev;



	orig_bio->bi_status = bio->bi_status;



	bio_end_io_acct(orig_bio, md_io_acct->start_time);

	bio_put(bio);

	bio_endio(orig_bio);



	percpu_ref_put(&mddev->active_io);

}



/*
@@ -8649,10 +8652,13 @@ void md_account_bio(struct mddev *mddev, struct bio **bio) 
	if (!blk_queue_io_stat(bdev->bd_disk->queue))

		return;



	percpu_ref_get(&mddev->active_io);



	clone = bio_alloc_clone(bdev, *bio, GFP_NOIO, &mddev->io_acct_set);

	md_io_acct = container_of(clone, struct md_io_acct, bio_clone);

	md_io_acct->orig_bio = *bio;

	md_io_acct->start_time = bio_start_io_acct(*bio);

	md_io_acct->mddev = mddev;



	clone->bi_end_io = md_end_io_acct;

	clone->bi_private = md_io_acct;

drivers/md/md.h

+4 −3
Original line number Diff line number Diff line
@@ -710,6 +710,7 @@ struct md_thread { 
};



struct md_io_acct {

	struct mddev	*mddev;

	struct bio	*orig_bio;

	unsigned long	start_time;

	struct bio	bio_clone;