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block: define bvec_iter as __packed __aligned(4) 

In commit 19416123ab ("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: 19416123ab ("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>
This commit is contained in:
Ming Lei 2024-02-25 11:01:41 +08:00 committed by Linus Torvalds
parent 7fd664466a
commit 7838b46561
1 changed files with 1 additions and 1 deletions
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2
include/linux/bvec.h
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@ -83,7 +83,7 @@ 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;