linux-kernel - [PATCH 7/8][next] md/raid5: Avoid -Wflex-array-member-not-at-end warnings

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Message-ID: <e6dfc07ceb44da02e9e012114a5ae44e4a9ec3d0.1739957534.git.gustavoars@kernel.org>
Date: Mon, 24 Feb 2025 20:30:45 +1030
From: "Gustavo A. R. Silva" <gustavoars@...nel.org>
To: Song Liu <song@...nel.org>, Yu Kuai <yukuai3@...wei.com>
Cc: linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	linux-hardening@...r.kernel.org
Subject: [PATCH 7/8][next] md/raid5: Avoid -Wflex-array-member-not-at-end
 warnings

-Wflex-array-member-not-at-end was introduced in GCC-14, and we are
getting ready to enable it, globally.

Change the type of the middle struct members currently causing trouble
from `struct bio` to `struct bio_hdr`.

We also use `container_of()` whenever we need to retrieve a pointer to
the flexible structure `struct bio`, through which we can access the
flexible-array member in it, if necessary.

With these changes fix 10 of the following warnings:

drivers/md/raid5.h:262:33: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
drivers/md/raid5.h:262:38: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]

Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
---
 drivers/md/raid5.c | 10 +++++-----
 drivers/md/raid5.h |  2 +-
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 5c79429acc64..76981d8cbc5d 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -1178,8 +1178,8 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
 
 again:
 		dev = &sh->dev[i];
-		bi = &dev->req;
-		rbi = &dev->rreq; /* For writing to replacement */
+		bi = container_of(&dev->req, struct bio, __hdr);
+		rbi = container_of(&dev->rreq, struct bio, __hdr); /* For writing to replacement */
 
 		rdev = conf->disks[i].rdev;
 		rrdev = conf->disks[i].replacement;
@@ -2720,7 +2720,7 @@ static void raid5_end_read_request(struct bio * bi)
 	sector_t s;
 
 	for (i=0 ; i<disks; i++)
-		if (bi == &sh->dev[i].req)
+		if (bi == container_of(&sh->dev[i].req, struct bio, __hdr))
 			break;
 
 	pr_debug("end_read_request %llu/%d, count: %d, error %d.\n",
@@ -2848,11 +2848,11 @@ static void raid5_end_write_request(struct bio *bi)
 	int replacement = 0;
 
 	for (i = 0 ; i < disks; i++) {
-		if (bi == &sh->dev[i].req) {
+		if (bi == container_of(&sh->dev[i].req, struct bio, __hdr)) {
 			rdev = conf->disks[i].rdev;
 			break;
 		}
-		if (bi == &sh->dev[i].rreq) {
+		if (bi == container_of(&sh->dev[i].rreq, struct bio, __hdr)) {
 			rdev = conf->disks[i].replacement;
 			if (rdev)
 				replacement = 1;
diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index eafc6e9ed6ee..3df59302e953 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -259,7 +259,7 @@ struct stripe_head {
 		/* rreq and rvec are used for the replacement device when
 		 * writing data to both devices.
 		 */
-		struct bio	req, rreq;
+		struct bio_hdr	req, rreq;
 		struct bio_vec	vec, rvec;
 		struct page	*page, *orig_page;
 		unsigned int    offset;     /* offset of the page */
-- 
2.43.0