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Subject[PATCH 4.12 076/196] md: fix deadlock between mddev_suspend() and md_write_start()
Date
4.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: NeilBrown <neilb@suse.com>

commit cc27b0c78c79680d128dbac79de0d40556d041bb upstream.

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)
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/md/faulty.c | 5 +++--
drivers/md/linear.c | 7 ++++---
drivers/md/md.c | 22 +++++++++++++++++-----
drivers/md/md.h | 4 ++--
drivers/md/multipath.c | 8 ++++----
drivers/md/raid0.c | 7 ++++---
drivers/md/raid1.c | 11 +++++++----
drivers/md/raid10.c | 10 ++++++----
drivers/md/raid5.c | 17 +++++++++--------
9 files changed, 56 insertions(+), 35 deletions(-)

--- a/drivers/md/faulty.c
+++ b/drivers/md/faulty.c
@@ -170,7 +170,7 @@ static void add_sector(struct faulty_con
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 m
* 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 m
bio->bi_bdev = conf->rdev->bdev;

generic_make_request(bio);
+ return true;
}

static void faulty_status(struct seq_file *seq, struct mddev *mddev)
--- a/drivers/md/linear.c
+++ b/drivers/md/linear.c
@@ -245,7 +245,7 @@ static void linear_free(struct mddev *md
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 m

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 m
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)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -277,7 +277,7 @@ static blk_qc_t md_make_request(struct r
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 r
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,
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);

--- 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_t
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);
--- a/drivers/md/multipath.c
+++ b/drivers/md/multipath.c
@@ -106,7 +106,7 @@ static void multipath_end_request(struct
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(struc

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(struc
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(struc
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)
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -548,7 +548,7 @@ static void raid0_handle_discard(struct
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 md

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 md
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)
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1321,7 +1321,6 @@ static void raid1_write_request(struct m
* 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) ||
@@ -1553,13 +1552,13 @@ static void raid1_write_request(struct m
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;
}

/*
@@ -1574,8 +1573,12 @@ static void raid1_make_request(struct md

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)
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -1303,8 +1303,6 @@ static void raid10_write_request(struct
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
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 m

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 m

/* 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)
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -5479,7 +5479,6 @@ static void make_discard_request(struct
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
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 md
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 md
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 md
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) {
@@ -5743,6 +5743,7 @@ static void raid5_make_request(struct md
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);

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