[PATCH 6.1 203/215] block: define bvec_iter as __packed __aligned(4)

Greg Kroah-Hartman
2024-03-04T21:52:38Z

From: Ming Lei <ming.lei@redhat.com>

[ Upstream commit 7838b4656110d950afdd92a081cc0f33e23e0ea8 ]

In commit 19416123ab3e ("block: define 'struct bvec_iter' as packed"),
what we need is to save the 4byte padding, and avoid `bio` to spread on
one extra cache line.

It is enough to define it as '__packed __aligned(4)', as '__packed'
alone means byte aligned, and can cause compiler to generate horrible
code on architectures that don't support unaligned access in case that
bvec_iter is embedded in other structures.

Cc: Mikulas Patocka <mpatocka@redhat.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Fixes: 19416123ab3e ("block: define 'struct bvec_iter' as packed")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/linux/bvec.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/bvec.h b/include/linux/bvec.h
index 9e3dac51eb26b..d4dbaae8b5218 100644
--- a/include/linux/bvec.h
+++ b/include/linux/bvec.h
@@ -59,7 +59,7 @@ struct bvec_iter {

unsigned int bi_bvec_done; /* number of bytes completed in
current bvec */
-} __packed;
+} __packed __aligned(4);

struct bvec_iter_all {
struct bio_vec bv;
--
2.43.0