linux-kernel - [PATCH v1 6/7] md/raid5-ppl: Annotate with rcu_dereference

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Message-Id: <20220407165713.9243-7-logang@deltatee.com>
Date:   Thu,  7 Apr 2022 10:57:12 -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 6/7] md/raid5-ppl: Annotate with rcu_dereference_protected()

To suppress the last remaining sparse warnings about accessing
rdev, add rcu_dereference_protected calls to a couple places
in raid5-ppl. All of these places are called under raid5_run and
therefore are occurring before the array has started and is thus
safe.

There's no sensible check to do for the second argument of
rcu_dereference_protected() so a comment is added instead.

Signed-off-by: Logan Gunthorpe <logang@...tatee.com>
---
 drivers/md/raid5-ppl.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/md/raid5-ppl.c b/drivers/md/raid5-ppl.c
index d3962d92df18..55d065a87b89 100644
--- a/drivers/md/raid5-ppl.c
+++ b/drivers/md/raid5-ppl.c
@@ -883,7 +883,9 @@ static int ppl_recover_entry(struct ppl_log *log, struct ppl_header_entry *e,
 				 (unsigned long long)r_sector, dd_idx,
 				 (unsigned long long)sector);
 
-			rdev = conf->disks[dd_idx].rdev;
+			/* Array has not started so rcu dereference is safe */
+			rdev = rcu_dereference_protected(
+					conf->disks[dd_idx].rdev, 1);
 			if (!rdev || (!test_bit(In_sync, &rdev->flags) &&
 				      sector >= rdev->recovery_offset)) {
 				pr_debug("%s:%*s data member disk %d missing\n",
@@ -934,7 +936,10 @@ static int ppl_recover_entry(struct ppl_log *log, struct ppl_header_entry *e,
 		parity_sector = raid5_compute_sector(conf, r_sector_first + i,
 				0, &disk, &sh);
 		BUG_ON(sh.pd_idx != le32_to_cpu(e->parity_disk));
-		parity_rdev = conf->disks[sh.pd_idx].rdev;
+
+		/* Array has not started so rcu dereference is safe */
+		parity_rdev = rcu_dereference_protected(
+					conf->disks[sh.pd_idx].rdev, 1);
 
 		BUG_ON(parity_rdev->bdev->bd_dev != log->rdev->bdev->bd_dev);
 		pr_debug("%s:%*s write parity at sector %llu, disk %s\n",
@@ -1404,7 +1409,9 @@ int ppl_init_log(struct r5conf *conf)
 
 	for (i = 0; i < ppl_conf->count; i++) {
 		struct ppl_log *log = &ppl_conf->child_logs[i];
-		struct md_rdev *rdev = conf->disks[i].rdev;
+		/* Array has not started so rcu dereference is safe */
+		struct md_rdev *rdev =
+			rcu_dereference_protected(conf->disks[i].rdev, 1);
 
 		mutex_init(&log->io_mutex);
 		spin_lock_init(&log->io_list_lock);
-- 
2.30.2