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Message-Id: <20220407165713.9243-4-logang@deltatee.com>
Date: Thu, 7 Apr 2022 10:57:09 -0600
From: Logan Gunthorpe <logang@...tatee.com>
To: linux-kernel@...r.kernel.org, linux-raid@...r.kernel.org,
Song Liu <song@...nel.org>
Cc: Guoqing Jiang <guoqing.jiang@...ux.dev>,
Logan Gunthorpe <logang@...tatee.com>
Subject: [PATCH v1 3/7] 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: Logan Gunthorpe <logang@...tatee.com>
---
drivers/md/raid5.c | 46 ++++++++++++++++++++++++++--------------------
drivers/md/raid5.h | 3 ++-
2 files changed, 28 insertions(+), 21 deletions(-)
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index c0e373a02d3a..4815f5351818 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -6288,7 +6288,7 @@ 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;
@@ -7320,11 +7320,11 @@ 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)) {
@@ -7631,11 +7631,11 @@ 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");
@@ -7836,8 +7836,8 @@ 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) {
@@ -7848,14 +7848,16 @@ 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)
@@ -7906,8 +7908,9 @@ 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) {
@@ -7925,9 +7928,9 @@ 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;
@@ -7947,7 +7950,8 @@ 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;
@@ -7958,7 +7962,7 @@ 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) {
@@ -7966,17 +7970,19 @@ 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);
diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index 61bc2e1f1b4e..638d29863503 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -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 */
};
--
2.30.2
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