diff options
| author | Xiao Ni <xni@redhat.com> | 2021-08-18 08:57:48 +0300 |
|---|---|---|
| committer | Song Liu <songliubraving@fb.com> | 2021-08-26 19:04:15 +0300 |
| commit | 46d4703b1db4c86ab5acb2331b10df999f005e8e (patch) | |
| tree | 322f0fd2d0c863d44d4637ad22809928a763adea /drivers/md | |
| parent | 7ee656c3ac3d047b4cf1269f83ac9d6c0bba916b (diff) | |
| download | linux-46d4703b1db4c86ab5acb2331b10df999f005e8e.tar.xz | |
md/raid10: Remove unnecessary rcu_dereference in raid10_handle_discard
We are seeing the following warning in raid10_handle_discard.
[ 695.110751] =============================
[ 695.131439] WARNING: suspicious RCU usage
[ 695.151389] 4.18.0-319.el8.x86_64+debug #1 Not tainted
[ 695.174413] -----------------------------
[ 695.192603] drivers/md/raid10.c:1776 suspicious
rcu_dereference_check() usage!
[ 695.225107] other info that might help us debug this:
[ 695.260940] rcu_scheduler_active = 2, debug_locks = 1
[ 695.290157] no locks held by mkfs.xfs/10186.
In the first loop of function raid10_handle_discard. It already
determines which disk need to handle discard request and add the
rdev reference count rdev->nr_pending. So the conf->mirrors will
not change until all bios come back from underlayer disks. It
doesn't need to use rcu_dereference to get rdev.
Cc: stable@vger.kernel.org
Fixes: d30588b2731f ('md/raid10: improve raid10 discard request')
Signed-off-by: Xiao Ni <xni@redhat.com>
Acked-by: Guoqing Jiang <guoqing.jiang@linux.dev>
Signed-off-by: Song Liu <songliubraving@fb.com>
Diffstat (limited to 'drivers/md')
| -rw-r--r-- | drivers/md/raid10.c | 14 |
1 files changed, 10 insertions, 4 deletions
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c index 16977e8e075d..d5d92337e35e 100644 --- a/drivers/md/raid10.c +++ b/drivers/md/raid10.c @@ -1712,6 +1712,11 @@ retry_discard: } else r10_bio->master_bio = (struct bio *)first_r10bio; + /* + * first select target devices under rcu_lock and + * inc refcount on their rdev. Record them by setting + * bios[x] to bio + */ rcu_read_lock(); for (disk = 0; disk < geo->raid_disks; disk++) { struct md_rdev *rdev = rcu_dereference(conf->mirrors[disk].rdev); @@ -1743,9 +1748,6 @@ retry_discard: for (disk = 0; disk < geo->raid_disks; disk++) { sector_t dev_start, dev_end; struct bio *mbio, *rbio = NULL; - struct md_rdev *rdev = rcu_dereference(conf->mirrors[disk].rdev); - struct md_rdev *rrdev = rcu_dereference( - conf->mirrors[disk].replacement); /* * Now start to calculate the start and end address for each disk. @@ -1775,9 +1777,12 @@ retry_discard: /* * It only handles discard bio which size is >= stripe size, so - * dev_end > dev_start all the time + * dev_end > dev_start all the time. + * It doesn't need to use rcu lock to get rdev here. We already + * add rdev->nr_pending in the first loop. */ if (r10_bio->devs[disk].bio) { + struct md_rdev *rdev = conf->mirrors[disk].rdev; mbio = bio_clone_fast(bio, GFP_NOIO, &mddev->bio_set); mbio->bi_end_io = raid10_end_discard_request; mbio->bi_private = r10_bio; @@ -1790,6 +1795,7 @@ retry_discard: bio_endio(mbio); } if (r10_bio->devs[disk].repl_bio) { + struct md_rdev *rrdev = conf->mirrors[disk].replacement; rbio = bio_clone_fast(bio, GFP_NOIO, &mddev->bio_set); rbio->bi_end_io = raid10_end_discard_request; rbio->bi_private = r10_bio; |