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| author | NeilBrown <neilb@suse.de> | 2014-12-15 12:56:59 +1100 |
|---|---|---|
| committer | NeilBrown <neilb@suse.de> | 2015-02-06 09:32:55 +1100 |
| commit | f97fcad38f2ecf2e34b6f0ab93f74f2978dbe008 (patch) | |
| tree | bff93531bc4bf444adf29337202b4814359d8a61 | |
| parent | 978a7a47cae79ae7a7b5a1e80bfcaef6ee700312 (diff) | |
| download | talos-obmc-linux-f97fcad38f2ecf2e34b6f0ab93f74f2978dbe008.tar.gz talos-obmc-linux-f97fcad38f2ecf2e34b6f0ab93f74f2978dbe008.zip | |
md: remove need for mddev_lock() in md_seq_show()
The only access in md_seq_show that could suffer from races
not protected by ->lock is walking the rdev list.
This can receive sufficient protection from 'rcu'.
So use rdev_for_each_rcu() and get rid of mddev_lock().
Now reading /proc/mdstat will never block in md_seq_show.
Signed-off-by: NeilBrown <neilb@suse.de>
| -rw-r--r-- | drivers/md/md.c | 8 |
1 files changed, 3 insertions, 5 deletions
diff --git a/drivers/md/md.c b/drivers/md/md.c index 4db4e4146a35..eb0c3b576d7d 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -6950,9 +6950,6 @@ static int md_seq_show(struct seq_file *seq, void *v) return 0; } - if (mddev_lock(mddev) < 0) - return -EINTR; - spin_lock(&mddev->lock); if (mddev->pers || mddev->raid_disks || !list_empty(&mddev->disks)) { seq_printf(seq, "%s : %sactive", mdname(mddev), @@ -6966,7 +6963,8 @@ static int md_seq_show(struct seq_file *seq, void *v) } sectors = 0; - rdev_for_each(rdev, mddev) { + rcu_read_lock(); + rdev_for_each_rcu(rdev, mddev) { char b[BDEVNAME_SIZE]; seq_printf(seq, " %s[%d]", bdevname(rdev->bdev,b), rdev->desc_nr); @@ -6982,6 +6980,7 @@ static int md_seq_show(struct seq_file *seq, void *v) seq_printf(seq, "(R)"); sectors += rdev->sectors; } + rcu_read_unlock(); if (!list_empty(&mddev->disks)) { if (mddev->pers) @@ -7025,7 +7024,6 @@ static int md_seq_show(struct seq_file *seq, void *v) seq_printf(seq, "\n"); } spin_unlock(&mddev->lock); - mddev_unlock(mddev); return 0; } |
