From: NeilBrown <neilb@suse.de>
To: linux-raid@vger.kernel.org
Subject: [md PATCH 15/26] md: remove need for mddev_lock() in md_seq_show()
Date: Wed, 04 Feb 2015 08:42:29 +1100 [thread overview]
Message-ID: <20150203214229.3448.55762.stgit@notabene.brown> (raw)
In-Reply-To: <20150203213948.3448.80258.stgit@notabene.brown>
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>
---
drivers/md/md.c | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 421d47e2d457..4caa414fe6a3 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;
}
next prev parent reply other threads:[~2015-02-03 21:42 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-03 21:42 [md PATCH 00/26] Pending md patches NeilBrown
2015-02-03 21:42 ` [md PATCH 02/26] md/raid5: separate large if clause out of fetch_block() NeilBrown
2015-02-03 21:42 ` [md PATCH 01/26] md: do_release_stripe(): No need to call md_wakeup_thread() twice NeilBrown
2015-02-03 21:42 ` [md PATCH 05/26] md/raid5: need_this_block: tidy/fix last condition NeilBrown
2015-02-03 21:42 ` [md PATCH 03/26] md/raid5: separate out the easy conditions in need_this_block NeilBrown
2015-02-03 21:42 ` [md PATCH 06/26] md: rename mddev->write_lock to mddev->lock NeilBrown
2015-02-03 21:42 ` [md PATCH 04/26] md/raid5: need_this_block: start simplifying the last two conditions NeilBrown
2015-02-03 21:42 ` [md PATCH 07/26] md: make ->congested robust against personality changes NeilBrown
2015-02-03 21:42 ` [md PATCH 11/26] md: rename ->stop to ->free NeilBrown
2015-02-03 21:42 ` [md PATCH 08/26] md: make merge_bvec_fn more robust in face of personality changes NeilBrown
2015-02-03 21:42 ` [md PATCH 20/26] md: tidy up set_bitmap_file NeilBrown
2015-02-03 21:42 ` [md PATCH 18/26] md: remove mddev_lock from rdev_attr_show() NeilBrown
2015-02-03 21:42 ` [md PATCH 17/26] md: remove mddev_lock() from md_attr_show() NeilBrown
2015-02-03 21:42 ` [md PATCH 09/26] md/linear: remove rcu protections in favour of suspend/resume NeilBrown
2015-02-03 21:42 ` NeilBrown [this message]
2015-02-03 21:42 ` [md PATCH 10/26] md: split detach operation out from ->stop NeilBrown
2015-02-03 21:42 ` [md PATCH 13/26] md: protect ->pers changes with mddev->lock NeilBrown
2015-02-03 21:42 ` [md PATCH 12/26] md: level_store: group all important changes into one place NeilBrown
2015-02-03 21:42 ` [md PATCH 16/26] md/raid5: use ->lock to protect accessing raid5 sysfs attributes NeilBrown
2015-02-03 21:42 ` [md PATCH 19/26] md: remove unnecessary 'buf' from get_bitmap_file NeilBrown
2015-02-03 21:42 ` [md PATCH 14/26] md/bitmap: protect clearing of ->bitmap by mddev->lock NeilBrown
2015-02-03 21:42 ` [md PATCH 25/26] md: make reconfig_mutex optional for writes to md sysfs files NeilBrown
2015-02-03 21:42 ` [md PATCH 22/26] md: minor cleanup in safe_delay_store NeilBrown
2015-02-03 21:42 ` [md PATCH 21/26] md: move GET_BITMAP_FILE ioctl out from mddev_lock NeilBrown
2015-02-03 21:42 ` [md PATCH 26/26] md: wakeup thread upon rdev_dec_pending() NeilBrown
2015-02-03 21:42 ` [md PATCH 23/26] md: use mddev->lock to protect updates to resync_{min, max} NeilBrown
2015-02-03 21:42 ` [md PATCH 24/26] md: move mddev_lock and related to md.h NeilBrown
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