Commit b0920ede authored by Logan Gunthorpe's avatar Logan Gunthorpe Committed by Song Liu
Browse files

md/raid5: Add __rcu annotation to struct disk_info 



rdev and replacement are protected in some circumstances with
rcu_dereference and synchronize_rcu (in raid5_remove_disk()). However,
they were not annotated with __rcu so a sparse warning is emitted for
every rcu_dereference() call.

Add the __rcu annotation and fix up the initialization with
RCU_INIT_POINTER, all pointer modifications with rcu_assign_pointer(),
a few cases where the pointer value is tested with rcu_access_pointer()
and one case where READ_ONCE() is used instead of rcu_dereference(),
a case in print_raid5_conf() that should have rcu_dereference() and
rcu_read_[un]lock() calls.

Additional sparse issues will be fixed up in further commits.

Signed-off-by: default avatarLogan Gunthorpe <logang@deltatee.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarSong Liu <song@kernel.org>
parent 3d9a644c

drivers/md/raid5.c

+26 −20
Original line number Diff line number Diff line
@@ -6285,7 +6285,7 @@ static inline sector_t raid5_sync_request(struct mddev *mddev, sector_t sector_n 
	 */

	rcu_read_lock();

	for (i = 0; i < conf->raid_disks; i++) {

		struct md_rdev *rdev = READ_ONCE(conf->disks[i].rdev);

		struct md_rdev *rdev = rcu_dereference(conf->disks[i].rdev);



		if (rdev == NULL || test_bit(Faulty, &rdev->flags))

			still_degraded = 1;
@@ -7317,11 +7317,11 @@ static struct r5conf *setup_conf(struct mddev *mddev) 
		if (test_bit(Replacement, &rdev->flags)) {

			if (disk->replacement)

				goto abort;

			disk->replacement = rdev;

			RCU_INIT_POINTER(disk->replacement, rdev);

		} else {

			if (disk->rdev)

				goto abort;

			disk->rdev = rdev;

			RCU_INIT_POINTER(disk->rdev, rdev);

		}



		if (test_bit(In_sync, &rdev->flags)) {
@@ -7628,11 +7628,11 @@ static int raid5_run(struct mddev *mddev) 
			rdev = conf->disks[i].replacement;

			conf->disks[i].replacement = NULL;

			clear_bit(Replacement, &rdev->flags);

			conf->disks[i].rdev = rdev;

			rcu_assign_pointer(conf->disks[i].rdev, rdev);

		}

		if (!rdev)

			continue;

		if (conf->disks[i].replacement &&

		if (rcu_access_pointer(conf->disks[i].replacement) &&

		    conf->reshape_progress != MaxSector) {

			/* replacements and reshape simply do not mix. */

			pr_warn("md: cannot handle concurrent replacement and reshape.\n");
@@ -7829,8 +7829,8 @@ static void raid5_status(struct seq_file *seq, struct mddev *mddev) 


static void print_raid5_conf (struct r5conf *conf)

{

	struct md_rdev *rdev;

	int i;

	struct disk_info *tmp;



	pr_debug("RAID conf printout:\n");

	if (!conf) {
@@ -7841,14 +7841,16 @@ static void print_raid5_conf (struct r5conf *conf) 
	       conf->raid_disks,

	       conf->raid_disks - conf->mddev->degraded);



	rcu_read_lock();

	for (i = 0; i < conf->raid_disks; i++) {

		char b[BDEVNAME_SIZE];

		tmp = conf->disks + i;

		if (tmp->rdev)

		rdev = rcu_dereference(conf->disks[i].rdev);

		if (rdev)

			pr_debug(" disk %d, o:%d, dev:%s\n",

			       i, !test_bit(Faulty, &tmp->rdev->flags),

			       bdevname(tmp->rdev->bdev, b));

			       i, !test_bit(Faulty, &rdev->flags),

			       bdevname(rdev->bdev, b));

	}

	rcu_read_unlock();

}



static int raid5_spare_active(struct mddev *mddev)
@@ -7899,8 +7901,9 @@ static int raid5_remove_disk(struct mddev *mddev, struct md_rdev *rdev) 
	struct r5conf *conf = mddev->private;

	int err = 0;

	int number = rdev->raid_disk;

	struct md_rdev **rdevp;

	struct md_rdev __rcu **rdevp;

	struct disk_info *p = conf->disks + number;

	struct md_rdev *tmp;



	print_raid5_conf(conf);

	if (test_bit(Journal, &rdev->flags) && conf->log) {
@@ -7918,9 +7921,9 @@ static int raid5_remove_disk(struct mddev *mddev, struct md_rdev *rdev) 
		log_exit(conf);

		return 0;

	}

	if (rdev == p->rdev)

	if (rdev == rcu_access_pointer(p->rdev))

		rdevp = &p->rdev;

	else if (rdev == p->replacement)

	else if (rdev == rcu_access_pointer(p->replacement))

		rdevp = &p->replacement;

	else

		return 0;
@@ -7940,7 +7943,8 @@ static int raid5_remove_disk(struct mddev *mddev, struct md_rdev *rdev) 
	if (!test_bit(Faulty, &rdev->flags) &&

	    mddev->recovery_disabled != conf->recovery_disabled &&

	    !has_failed(conf) &&

	    (!p->replacement || p->replacement == rdev) &&

	    (!rcu_access_pointer(p->replacement) ||

	     rcu_access_pointer(p->replacement) == rdev) &&

	    number < conf->raid_disks) {

		err = -EBUSY;

		goto abort;
@@ -7951,7 +7955,7 @@ static int raid5_remove_disk(struct mddev *mddev, struct md_rdev *rdev) 
		if (atomic_read(&rdev->nr_pending)) {

			/* lost the race, try later */

			err = -EBUSY;

			*rdevp = rdev;

			rcu_assign_pointer(*rdevp, rdev);

		}

	}

	if (!err) {
@@ -7959,17 +7963,19 @@ static int raid5_remove_disk(struct mddev *mddev, struct md_rdev *rdev) 
		if (err)

			goto abort;

	}

	if (p->replacement) {



	tmp = rcu_access_pointer(p->replacement);

	if (tmp) {

		/* We must have just cleared 'rdev' */

		p->rdev = p->replacement;

		clear_bit(Replacement, &p->replacement->flags);

		rcu_assign_pointer(p->rdev, tmp);

		clear_bit(Replacement, &tmp->flags);

		smp_mb(); /* Make sure other CPUs may see both as identical

			   * but will never see neither - if they are careful

			   */

		p->replacement = NULL;

		rcu_assign_pointer(p->replacement, NULL);



		if (!err)

			err = log_modify(conf, p->rdev, true);

			err = log_modify(conf, tmp, true);

	}



	clear_bit(WantReplacement, &rdev->flags);

drivers/md/raid5.h

+2 −1
Original line number Diff line number Diff line
@@ -473,7 +473,8 @@ enum { 
 */



struct disk_info {

	struct md_rdev	*rdev, *replacement;

	struct md_rdev	__rcu *rdev;

	struct md_rdev  __rcu *replacement;

	struct page	*extra_page; /* extra page to use in prexor */

};