[PATCH 0/8][next] Avoid a couple hundred -Wflex-array-member-not-at-end warnings

[PATCH 0/8][next] Avoid a couple hundred -Wflex-array-member-not-at-end warnings

[Gustavo A. R. Silva]

This patch series aims to fix a couple hundred -Wflex-array-member-not-at-end
warnings by creating a new tagged struct `struct bio_hdr` within flexible
structure `struct bio`.

This new tagged struct will be used to fix problematic declarations
of middle-flex-arrays in composite structs, like these[1][2][3], for
instance.

[1] https://git.kernel.org/linus/a7e8997ae18c42d3
[2] https://git.kernel.org/linus/c1ddb29709e675ea
[3] https://git.kernel.org/linus/57be3d3562ca4aa6

Gustavo A. R. Silva (8):
  block: blk_types.h: Use struct_group_tagged() in flex struct bio
  md/raid5-ppl: Avoid -Wflex-array-member-not-at-end warning
  xfs: Avoid -Wflex-array-member-not-at-end warnings
  erofs: Avoid -Wflex-array-member-not-at-end warnings
  btrfs: Avoid -Wflex-array-member-not-at-end warnings
  nvme: target: Avoid -Wflex-array-member-not-at-end warnings
  md/raid5: Avoid -Wflex-array-member-not-at-end warnings
  bcache: Avoid -Wflex-array-member-not-at-end warnings

 drivers/md/bcache/bcache.h     |  4 +-
 drivers/md/bcache/journal.c    | 10 ++--
 drivers/md/bcache/journal.h    |  4 +-
 drivers/md/bcache/super.c      |  8 ++--
 drivers/md/raid5-ppl.c         |  8 ++--
 drivers/md/raid5.c             | 10 ++--
 drivers/md/raid5.h             |  2 +-
 drivers/nvme/target/nvmet.h    |  4 +-
 drivers/nvme/target/passthru.c |  2 +-
 drivers/nvme/target/zns.c      |  2 +-
 fs/btrfs/disk-io.c             |  4 +-
 fs/btrfs/volumes.h             |  2 +-
 fs/erofs/fileio.c              | 25 ++++++----
 fs/erofs/fscache.c             | 13 +++---
 fs/xfs/xfs_log.c               | 15 +++---
 fs/xfs/xfs_log_priv.h          |  2 +-
 include/linux/blk_types.h      | 84 ++++++++++++++++++----------------
 17 files changed, 107 insertions(+), 92 deletions(-)

-- 
2.43.0

[PATCH 2/8][next] md/raid5-ppl: Avoid -Wflex-array-member-not-at-end warning

[Gustavo A. R. Silva]

-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 member 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 the following warning:
drivers/md/raid5-ppl.c:153:20: 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@kernel.org>
---
 drivers/md/raid5-ppl.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/md/raid5-ppl.c b/drivers/md/raid5-ppl.c
index c0fb335311aa..f4333c644b67 100644
--- a/drivers/md/raid5-ppl.c
+++ b/drivers/md/raid5-ppl.c
@@ -150,7 +150,7 @@ struct ppl_io_unit {
 	bool submitted;			/* true if write to log started */
 
 	/* inline bio and its biovec for submitting the iounit */
-	struct bio bio;
+	struct bio_hdr bio;
 	struct bio_vec biovec[PPL_IO_INLINE_BVECS];
 };
 
@@ -250,8 +250,8 @@ static struct ppl_io_unit *ppl_new_iounit(struct ppl_log *log,
 	INIT_LIST_HEAD(&io->stripe_list);
 	atomic_set(&io->pending_stripes, 0);
 	atomic_set(&io->pending_flushes, 0);
-	bio_init(&io->bio, log->rdev->bdev, io->biovec, PPL_IO_INLINE_BVECS,
-		 REQ_OP_WRITE | REQ_FUA);
+	bio_init(container_of(&io->bio, struct bio, __hdr), log->rdev->bdev,
+		 io->biovec, PPL_IO_INLINE_BVECS, REQ_OP_WRITE | REQ_FUA);
 
 	pplhdr = page_address(io->header_page);
 	clear_page(pplhdr);
@@ -430,7 +430,7 @@ static void ppl_submit_iounit(struct ppl_io_unit *io)
 	struct ppl_log *log = io->log;
 	struct ppl_conf *ppl_conf = log->ppl_conf;
 	struct ppl_header *pplhdr = page_address(io->header_page);
-	struct bio *bio = &io->bio;
+	struct bio *bio = container_of(&io->bio, struct bio, __hdr);
 	struct stripe_head *sh;
 	int i;
 
-- 
2.43.0

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

[Gustavo A. R. Silva]

-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@kernel.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