[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 5/8][next] btrfs: 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 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 32 of the following warnings:

fs/btrfs/volumes.h:178:20: 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>
---
 fs/btrfs/disk-io.c | 4 ++--
 fs/btrfs/volumes.h | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index f09db62e61a1..2fbaaa9ab3e3 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -3963,7 +3963,7 @@ static void btrfs_end_empty_barrier(struct bio *bio)
  */
 static void write_dev_flush(struct btrfs_device *device)
 {
-	struct bio *bio = &device->flush_bio;
+	struct bio *bio = container_of(&device->flush_bio, struct bio, __hdr);
 
 	device->last_flush_error = BLK_STS_OK;
 
@@ -3982,7 +3982,7 @@ static void write_dev_flush(struct btrfs_device *device)
  */
 static bool wait_dev_flush(struct btrfs_device *device)
 {
-	struct bio *bio = &device->flush_bio;
+	struct bio *bio = container_of(&device->flush_bio, struct bio, __hdr);
 
 	if (!test_and_clear_bit(BTRFS_DEV_STATE_FLUSH_SENT, &device->dev_state))
 		return false;
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 120f65e21eeb..6eb55103b3d1 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -175,7 +175,7 @@ struct btrfs_device {
 	u64 commit_bytes_used;
 
 	/* Bio used for flushing device barriers */
-	struct bio flush_bio;
+	struct bio_hdr flush_bio;
 	struct completion flush_wait;
 
 	/* per-device scrub information */
-- 
2.43.0