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

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
......@@ -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);
......
......@@ -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 */
};
......
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