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md: fix deadlock between mddev_suspend() and md_write_start()

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If mddev_suspend() races with md_write_start() we can deadlock
with mddev_suspend() waiting for the request that is currently
in md_write_start() to complete the ->make_request() call,
and md_write_start() waiting for the metadata to be updated
to mark the array as 'dirty'.
As metadata updates done by md_check_recovery() only happen then
the mddev_lock() can be claimed, and as mddev_suspend() is often
called with the lock held, these threads wait indefinitely for each
other.

We fix this by having md_write_start() abort if mddev_suspend()
is happening, and ->make_request() aborts if md_write_start()
aborted.
md_make_request() can detect this abort, decrease the ->active_io
count, and wait for mddev_suspend().

Reported-by: Nix <nix@esperi.org.uk>
Fix: 68866e425be2(MD: no sync IO while suspended)
Cc: stable@vger.kernel.org
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Shaohua Li <shli@fb.com>
This commit is contained in:
NeilBrown
2017-06-05 16:49:39 +10:00
committed by Shaohua Li
parent 63f700aab4
commit cc27b0c78c
9 changed files with 56 additions and 35 deletions
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11
drivers/md/raid1.c
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@@ -1321,7 +1321,6 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
* Continue immediately if no resync is active currently.
*/
md_write_start(mddev, bio); /* wait on superblock update early */
if ((bio_end_sector(bio) > mddev->suspend_lo &&
bio->bi_iter.bi_sector < mddev->suspend_hi) ||
@@ -1550,13 +1549,13 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
wake_up(&conf->wait_barrier);
}
static void raid1_make_request(struct mddev *mddev, struct bio *bio)
static bool raid1_make_request(struct mddev *mddev, struct bio *bio)
{
sector_t sectors;
if (unlikely(bio->bi_opf & REQ_PREFLUSH)) {
md_flush_request(mddev, bio);
return;
return true;
}
/*
@@ -1571,8 +1570,12 @@ static void raid1_make_request(struct mddev *mddev, struct bio *bio)
if (bio_data_dir(bio) == READ)
raid1_read_request(mddev, bio, sectors, NULL);
else
else {
if (!md_write_start(mddev,bio))
return false;
raid1_write_request(mddev, bio, sectors);
}
return true;
}
static void raid1_status(struct seq_file *seq, struct mddev *mddev)