From b5470dc5fc18a8ff6517c3bb538d1479e58ecb02 Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Fri, 27 Jun 2008 21:44:04 -0700 Subject: md: resolve external metadata handling deadlock in md_allow_write md_allow_write() marks the metadata dirty while holding mddev->lock and then waits for the write to complete. For externally managed metadata this causes a deadlock as userspace needs to take the lock to communicate that the metadata update has completed. Change md_allow_write() in the 'external' case to start the 'mark active' operation and then return -EAGAIN. The expected side effects while waiting for userspace to write 'active' to 'array_state' are holding off reshape (code currently handles -ENOMEM), cause some 'stripe_cache_size' change requests to fail, cause some GET_BITMAP_FILE ioctl requests to fall back to GFP_NOIO, and cause updates to 'raid_disks' to fail. Except for 'stripe_cache_size' changes these failures can be mitigated by coordinating with mdmon. md_write_start() still prevents writes from occurring until the metadata handler has had a chance to take action as it unconditionally waits for MD_CHANGE_CLEAN to be cleared. [neilb@suse.de: return -EAGAIN, try GFP_NOIO] Signed-off-by: Dan Williams --- drivers/md/raid1.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'drivers/md/raid1.c') diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c index f05d5983efb6..491dc2d4ad5f 100644 --- a/drivers/md/raid1.c +++ b/drivers/md/raid1.c @@ -2136,7 +2136,7 @@ static int raid1_reshape(mddev_t *mddev) conf_t *conf = mddev_to_conf(mddev); int cnt, raid_disks; unsigned long flags; - int d, d2; + int d, d2, err; /* Cannot change chunk_size, layout, or level */ if (mddev->chunk_size != mddev->new_chunk || @@ -2148,7 +2148,9 @@ static int raid1_reshape(mddev_t *mddev) return -EINVAL; } - md_allow_write(mddev); + err = md_allow_write(mddev); + if (err) + return err; raid_disks = mddev->raid_disks + mddev->delta_disks; -- cgit v1.2.3