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

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>

diff --git a/drivers/md/faulty.c b/drivers/md/faulty.c
index b0536cf..06a64d5 100644 (file)
--- a/drivers/md/faulty.c
+++ b/drivers/md/faulty.c
@@ -170,7 +170,7 @@ static void add_sector(struct faulty_conf *conf, sector_t start, int mode)
                conf->nfaults = n+1;
 }
 
-static void faulty_make_request(struct mddev *mddev, struct bio *bio)
+static bool faulty_make_request(struct mddev *mddev, struct bio *bio)
 {
        struct faulty_conf *conf = mddev->private;
        int failit = 0;
@@ -182,7 +182,7 @@ static void faulty_make_request(struct mddev *mddev, struct bio *bio)
                         * just fail immediately
                         */
                        bio_io_error(bio);
-                       return;
+                       return true;
                }
 
                if (check_sector(conf, bio->bi_iter.bi_sector,
@@ -224,6 +224,7 @@ static void faulty_make_request(struct mddev *mddev, struct bio *bio)
                bio->bi_bdev = conf->rdev->bdev;
 
        generic_make_request(bio);
+       return true;
 }
 
 static void faulty_status(struct seq_file *seq, struct mddev *mddev)

diff --git a/drivers/md/linear.c b/drivers/md/linear.c
index df6f2c9..5f1eb91 100644 (file)
--- a/drivers/md/linear.c
+++ b/drivers/md/linear.c
@@ -245,7 +245,7 @@ static void linear_free(struct mddev *mddev, void *priv)
        kfree(conf);
 }
 
-static void linear_make_request(struct mddev *mddev, struct bio *bio)
+static bool linear_make_request(struct mddev *mddev, struct bio *bio)
 {
        char b[BDEVNAME_SIZE];
        struct dev_info *tmp_dev;
@@ -254,7 +254,7 @@ static void linear_make_request(struct mddev *mddev, struct bio *bio)
 
        if (unlikely(bio->bi_opf & REQ_PREFLUSH)) {
                md_flush_request(mddev, bio);
-               return;
+               return true;
        }
 
        tmp_dev = which_dev(mddev, bio_sector);
@@ -292,7 +292,7 @@ static void linear_make_request(struct mddev *mddev, struct bio *bio)
                mddev_check_write_zeroes(mddev, bio);
                generic_make_request(bio);
        }
-       return;
+       return true;
 
 out_of_bounds:
        pr_err("md/linear:%s: make_request: Sector %llu out of bounds on dev %s: %llu sectors, offset %llu\n",
@@ -302,6 +302,7 @@ out_of_bounds:
               (unsigned long long)tmp_dev->rdev->sectors,
               (unsigned long long)start_sector);
        bio_io_error(bio);
+       return true;
 }
 
 static void linear_status (struct seq_file *seq, struct mddev *mddev)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 87edc34..d784701 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -277,7 +277,7 @@ static blk_qc_t md_make_request(struct request_queue *q, struct bio *bio)
                bio_endio(bio);
                return BLK_QC_T_NONE;
        }
-       smp_rmb(); /* Ensure implications of  'active' are visible */
+check_suspended:
        rcu_read_lock();
        if (mddev->suspended) {
                DEFINE_WAIT(__wait);
@@ -302,7 +302,11 @@ static blk_qc_t md_make_request(struct request_queue *q, struct bio *bio)
        sectors = bio_sectors(bio);
        /* bio could be mergeable after passing to underlayer */
        bio->bi_opf &= ~REQ_NOMERGE;
-       mddev->pers->make_request(mddev, bio);
+       if (!mddev->pers->make_request(mddev, bio)) {
+               atomic_dec(&mddev->active_io);
+               wake_up(&mddev->sb_wait);
+               goto check_suspended;
+       }
 
        cpu = part_stat_lock();
        part_stat_inc(cpu, &mddev->gendisk->part0, ios[rw]);
@@ -327,6 +331,7 @@ void mddev_suspend(struct mddev *mddev)
        if (mddev->suspended++)
                return;
        synchronize_rcu();
+       wake_up(&mddev->sb_wait);
        wait_event(mddev->sb_wait, atomic_read(&mddev->active_io) == 0);
        mddev->pers->quiesce(mddev, 1);
 
@@ -7950,12 +7955,14 @@ EXPORT_SYMBOL(md_done_sync);
  * If we need to update some array metadata (e.g. 'active' flag
  * in superblock) before writing, schedule a superblock update
  * and wait for it to complete.
+ * A return value of 'false' means that the write wasn't recorded
+ * and cannot proceed as the array is being suspend.
  */
-void md_write_start(struct mddev *mddev, struct bio *bi)
+bool md_write_start(struct mddev *mddev, struct bio *bi)
 {
        int did_change = 0;
        if (bio_data_dir(bi) != WRITE)
-               return;
+               return true;
 
        BUG_ON(mddev->ro == 1);
        if (mddev->ro == 2) {
@@ -7987,7 +7994,12 @@ void md_write_start(struct mddev *mddev, struct bio *bi)
        if (did_change)
                sysfs_notify_dirent_safe(mddev->sysfs_state);
        wait_event(mddev->sb_wait,
-                  !test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags));
+                  !test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags) && !mddev->suspended);
+       if (test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags)) {
+               percpu_ref_put(&mddev->writes_pending);
+               return false;
+       }
+       return true;
 }
 EXPORT_SYMBOL(md_write_start);
 

diff --git a/drivers/md/md.h b/drivers/md/md.h
index 0fa1de4..63d342d 100644 (file)
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -510,7 +510,7 @@ struct md_personality
        int level;
        struct list_head list;
        struct module *owner;
-       void (*make_request)(struct mddev *mddev, struct bio *bio);
+       bool (*make_request)(struct mddev *mddev, struct bio *bio);
        int (*run)(struct mddev *mddev);
        void (*free)(struct mddev *mddev, void *priv);
        void (*status)(struct seq_file *seq, struct mddev *mddev);
@@ -649,7 +649,7 @@ extern void md_wakeup_thread(struct md_thread *thread);
 extern void md_check_recovery(struct mddev *mddev);
 extern void md_reap_sync_thread(struct mddev *mddev);
 extern int mddev_init_writes_pending(struct mddev *mddev);
-extern void md_write_start(struct mddev *mddev, struct bio *bi);
+extern bool md_write_start(struct mddev *mddev, struct bio *bi);
 extern void md_write_inc(struct mddev *mddev, struct bio *bi);
 extern void md_write_end(struct mddev *mddev);
 extern void md_done_sync(struct mddev *mddev, int blocks, int ok);

diff --git a/drivers/md/multipath.c b/drivers/md/multipath.c
index e95d521..c8d985b 100644 (file)
--- a/drivers/md/multipath.c
+++ b/drivers/md/multipath.c
@@ -106,7 +106,7 @@ static void multipath_end_request(struct bio *bio)
        rdev_dec_pending(rdev, conf->mddev);
 }
 
-static void multipath_make_request(struct mddev *mddev, struct bio * bio)
+static bool multipath_make_request(struct mddev *mddev, struct bio * bio)
 {
        struct mpconf *conf = mddev->private;
        struct multipath_bh * mp_bh;
@@ -114,7 +114,7 @@ static void multipath_make_request(struct mddev *mddev, struct bio * bio)
 
        if (unlikely(bio->bi_opf & REQ_PREFLUSH)) {
                md_flush_request(mddev, bio);
-               return;
+               return true;
        }
 
        mp_bh = mempool_alloc(conf->pool, GFP_NOIO);
@@ -126,7 +126,7 @@ static void multipath_make_request(struct mddev *mddev, struct bio * bio)
        if (mp_bh->path < 0) {
                bio_io_error(bio);
                mempool_free(mp_bh, conf->pool);
-               return;
+               return true;
        }
        multipath = conf->multipaths + mp_bh->path;
 
@@ -141,7 +141,7 @@ static void multipath_make_request(struct mddev *mddev, struct bio * bio)
        mddev_check_writesame(mddev, &mp_bh->bio);
        mddev_check_write_zeroes(mddev, &mp_bh->bio);
        generic_make_request(&mp_bh->bio);
-       return;
+       return true;
 }
 
 static void multipath_status(struct seq_file *seq, struct mddev *mddev)

diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
index d6c0bc7..94d9ae9 100644 (file)
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -548,7 +548,7 @@ static void raid0_handle_discard(struct mddev *mddev, struct bio *bio)
        bio_endio(bio);
 }
 
-static void raid0_make_request(struct mddev *mddev, struct bio *bio)
+static bool raid0_make_request(struct mddev *mddev, struct bio *bio)
 {
        struct strip_zone *zone;
        struct md_rdev *tmp_dev;
@@ -559,12 +559,12 @@ static void raid0_make_request(struct mddev *mddev, struct bio *bio)
 
        if (unlikely(bio->bi_opf & REQ_PREFLUSH)) {
                md_flush_request(mddev, bio);
-               return;
+               return true;
        }
 
        if (unlikely((bio_op(bio) == REQ_OP_DISCARD))) {
                raid0_handle_discard(mddev, bio);
-               return;
+               return true;
        }
 
        bio_sector = bio->bi_iter.bi_sector;
@@ -599,6 +599,7 @@ static void raid0_make_request(struct mddev *mddev, struct bio *bio)
        mddev_check_writesame(mddev, bio);
        mddev_check_write_zeroes(mddev, bio);
        generic_make_request(bio);
+       return true;
 }
 
 static void raid0_status(struct seq_file *seq, struct mddev *mddev)

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index e1a7e3d..c71739b 100644 (file)
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -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)

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 797ed60..52acffa 100644 (file)
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -1303,8 +1303,6 @@ static void raid10_write_request(struct mddev *mddev, struct bio *bio,
        sector_t sectors;
        int max_sectors;
 
-       md_write_start(mddev, bio);
-
        /*
         * Register the new request and wait if the reconstruction
         * thread has put up a bar for new requests.
@@ -1525,7 +1523,7 @@ static void __make_request(struct mddev *mddev, struct bio *bio, int sectors)
                raid10_write_request(mddev, bio, r10_bio);
 }
 
-static void raid10_make_request(struct mddev *mddev, struct bio *bio)
+static bool raid10_make_request(struct mddev *mddev, struct bio *bio)
 {
        struct r10conf *conf = mddev->private;
        sector_t chunk_mask = (conf->geo.chunk_mask & conf->prev.chunk_mask);
@@ -1534,9 +1532,12 @@ static void raid10_make_request(struct mddev *mddev, struct bio *bio)
 
        if (unlikely(bio->bi_opf & REQ_PREFLUSH)) {
                md_flush_request(mddev, bio);
-               return;
+               return true;
        }
 
+       if (!md_write_start(mddev, bio))
+               return false;
+
        /*
         * If this request crosses a chunk boundary, we need to split
         * it.
@@ -1553,6 +1554,7 @@ static void raid10_make_request(struct mddev *mddev, struct bio *bio)
 
        /* In case raid10d snuck in to freeze_array */
        wake_up(&conf->wait_barrier);
+       return true;
 }
 
 static void raid10_status(struct seq_file *seq, struct mddev *mddev)

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index ec0f951..b218a42 100644 (file)
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -5479,7 +5479,6 @@ static void make_discard_request(struct mddev *mddev, struct bio *bi)
        last_sector = bi->bi_iter.bi_sector + (bi->bi_iter.bi_size>>9);
 
        bi->bi_next = NULL;
-       md_write_start(mddev, bi);
 
        stripe_sectors = conf->chunk_sectors *
                (conf->raid_disks - conf->max_degraded);
@@ -5549,11 +5548,10 @@ static void make_discard_request(struct mddev *mddev, struct bio *bi)
                release_stripe_plug(mddev, sh);
        }
 
-       md_write_end(mddev);
        bio_endio(bi);
 }
 
-static void raid5_make_request(struct mddev *mddev, struct bio * bi)
+static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
 {
        struct r5conf *conf = mddev->private;
        int dd_idx;
@@ -5569,10 +5567,10 @@ static void raid5_make_request(struct mddev *mddev, struct bio * bi)
                int ret = r5l_handle_flush_request(conf->log, bi);
 
                if (ret == 0)
-                       return;
+                       return true;
                if (ret == -ENODEV) {
                        md_flush_request(mddev, bi);
-                       return;
+                       return true;
                }
                /* ret == -EAGAIN, fallback */
                /*
@@ -5582,6 +5580,8 @@ static void raid5_make_request(struct mddev *mddev, struct bio * bi)
                do_flush = bi->bi_opf & REQ_PREFLUSH;
        }
 
+       if (!md_write_start(mddev, bi))
+               return false;
        /*
         * If array is degraded, better not do chunk aligned read because
         * later we might have to read it again in order to reconstruct
@@ -5591,18 +5591,18 @@ static void raid5_make_request(struct mddev *mddev, struct bio * bi)
            mddev->reshape_position == MaxSector) {
                bi = chunk_aligned_read(mddev, bi);
                if (!bi)
-                       return;
+                       return true;
        }
 
        if (unlikely(bio_op(bi) == REQ_OP_DISCARD)) {
                make_discard_request(mddev, bi);
-               return;
+               md_write_end(mddev);
+               return true;
        }
 
        logical_sector = bi->bi_iter.bi_sector & ~((sector_t)STRIPE_SECTORS-1);
        last_sector = bio_end_sector(bi);
        bi->bi_next = NULL;
-       md_write_start(mddev, bi);
 
        prepare_to_wait(&conf->wait_for_overlap, &w, TASK_UNINTERRUPTIBLE);
        for (;logical_sector < last_sector; logical_sector += STRIPE_SECTORS) {
@@ -5740,6 +5740,7 @@ static void raid5_make_request(struct mddev *mddev, struct bio * bi)
        if (rw == WRITE)
                md_write_end(mddev);
        bio_endio(bi);
+       return true;
 }
 
 static sector_t raid5_size(struct mddev *mddev, sector_t sectors, int raid_disks);