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Message-Id: <20220407165713.9243-6-logang@deltatee.com>
Date: Thu, 7 Apr 2022 10:57:11 -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 5/7] md/raid5: Annotate rdev/replacement access when mddev_lock is held
The mddev_lock should be held during raid5_remove_disk() which is when
the rdev/replacement pointers are modified. So any access to these
pointers marked __rcu should be safe whenever the mddev_lock is held.
There are numerous such access that currently produce sparse warnings.
Add a helper function, rdev_mdlock_deref() that wraps
rcu_dereference_protected() in all these instances.
This annotation fixes a number of sparse warnings.
Signed-off-by: Logan Gunthorpe <logang@...tatee.com>
---
drivers/md/raid5.c | 65 ++++++++++++++++++++++++++++++----------------
1 file changed, 43 insertions(+), 22 deletions(-)
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 0f29a2769cb3..fa955d23c88f 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -2658,6 +2658,18 @@ static struct md_rdev *rdev_pend_deref(struct md_rdev __rcu *rdev)
atomic_read(&rcu_access_pointer(rdev)->nr_pending));
}
+/*
+ * This helper wraps rcu_dereference_protected() and should be used
+ * when it is known that the mddev_lock() is held. This is safe
+ * seeing raid5_remove_disk() has the same lock held.
+ */
+static struct md_rdev *rdev_mdlock_deref(struct mddev *mddev,
+ struct md_rdev __rcu *rdev)
+{
+ return rcu_dereference_protected(rdev,
+ lockdep_is_held(&mddev->reconfig_mutex));
+}
+
static void raid5_end_read_request(struct bio * bi)
{
struct stripe_head *sh = bi->bi_private;
@@ -7635,10 +7647,11 @@ static int raid5_run(struct mddev *mddev)
for (i = 0; i < conf->raid_disks && conf->previous_raid_disks;
i++) {
- rdev = conf->disks[i].rdev;
+ rdev = rdev_mdlock_deref(mddev, conf->disks[i].rdev);
if (!rdev && conf->disks[i].replacement) {
/* The replacement is all we have yet */
- rdev = conf->disks[i].replacement;
+ rdev = rdev_mdlock_deref(mddev,
+ conf->disks[i].replacement);
conf->disks[i].replacement = NULL;
clear_bit(Replacement, &rdev->flags);
rcu_assign_pointer(conf->disks[i].rdev, rdev);
@@ -7874,36 +7887,38 @@ static int raid5_spare_active(struct mddev *mddev)
{
int i;
struct r5conf *conf = mddev->private;
- struct disk_info *tmp;
+ struct md_rdev *rdev, *replacement;
int count = 0;
unsigned long flags;
for (i = 0; i < conf->raid_disks; i++) {
- tmp = conf->disks + i;
- if (tmp->replacement
- && tmp->replacement->recovery_offset == MaxSector
- && !test_bit(Faulty, &tmp->replacement->flags)
- && !test_and_set_bit(In_sync, &tmp->replacement->flags)) {
+ rdev = rdev_mdlock_deref(mddev, conf->disks[i].rdev);
+ replacement = rdev_mdlock_deref(mddev,
+ conf->disks[i].replacement);
+ if (replacement
+ && replacement->recovery_offset == MaxSector
+ && !test_bit(Faulty, &replacement->flags)
+ && !test_and_set_bit(In_sync, &replacement->flags)) {
/* Replacement has just become active. */
- if (!tmp->rdev
- || !test_and_clear_bit(In_sync, &tmp->rdev->flags))
+ if (!rdev
+ || !test_and_clear_bit(In_sync, &rdev->flags))
count++;
- if (tmp->rdev) {
+ if (rdev) {
/* Replaced device not technically faulty,
* but we need to be sure it gets removed
* and never re-added.
*/
- set_bit(Faulty, &tmp->rdev->flags);
+ set_bit(Faulty, &rdev->flags);
sysfs_notify_dirent_safe(
- tmp->rdev->sysfs_state);
+ rdev->sysfs_state);
}
- sysfs_notify_dirent_safe(tmp->replacement->sysfs_state);
- } else if (tmp->rdev
- && tmp->rdev->recovery_offset == MaxSector
- && !test_bit(Faulty, &tmp->rdev->flags)
- && !test_and_set_bit(In_sync, &tmp->rdev->flags)) {
+ sysfs_notify_dirent_safe(replacement->sysfs_state);
+ } else if (rdev
+ && rdev->recovery_offset == MaxSector
+ && !test_bit(Faulty, &rdev->flags)
+ && !test_and_set_bit(In_sync, &rdev->flags)) {
count++;
- sysfs_notify_dirent_safe(tmp->rdev->sysfs_state);
+ sysfs_notify_dirent_safe(rdev->sysfs_state);
}
}
spin_lock_irqsave(&conf->device_lock, flags);
@@ -7968,6 +7983,7 @@ static int raid5_remove_disk(struct mddev *mddev, struct md_rdev *rdev)
}
*rdevp = NULL;
if (!test_bit(RemoveSynchronized, &rdev->flags)) {
+ lockdep_assert_held(&mddev->reconfig_mutex);
synchronize_rcu();
if (atomic_read(&rdev->nr_pending)) {
/* lost the race, try later */
@@ -8008,6 +8024,7 @@ static int raid5_add_disk(struct mddev *mddev, struct md_rdev *rdev)
int ret, err = -EEXIST;
int disk;
struct disk_info *p;
+ struct md_rdev *tmp;
int first = 0;
int last = conf->raid_disks - 1;
@@ -8065,7 +8082,8 @@ static int raid5_add_disk(struct mddev *mddev, struct md_rdev *rdev)
}
for (disk = first; disk <= last; disk++) {
p = conf->disks + disk;
- if (test_bit(WantReplacement, &p->rdev->flags) &&
+ tmp = rdev_mdlock_deref(mddev, p->rdev);
+ if (test_bit(WantReplacement, &tmp->flags) &&
p->replacement == NULL) {
clear_bit(In_sync, &rdev->flags);
set_bit(Replacement, &rdev->flags);
@@ -8356,6 +8374,7 @@ static void end_reshape(struct r5conf *conf)
static void raid5_finish_reshape(struct mddev *mddev)
{
struct r5conf *conf = mddev->private;
+ struct md_rdev *rdev;
if (!test_bit(MD_RECOVERY_INTR, &mddev->recovery)) {
@@ -8367,10 +8386,12 @@ static void raid5_finish_reshape(struct mddev *mddev)
for (d = conf->raid_disks ;
d < conf->raid_disks - mddev->delta_disks;
d++) {
- struct md_rdev *rdev = conf->disks[d].rdev;
+ rdev = rdev_mdlock_deref(mddev,
+ conf->disks[d].rdev);
if (rdev)
clear_bit(In_sync, &rdev->flags);
- rdev = conf->disks[d].replacement;
+ rdev = rdev_mdlock_deref(mddev,
+ conf->disks[d].replacement);
if (rdev)
clear_bit(In_sync, &rdev->flags);
}
--
2.30.2
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