Thread (24 messages) 24 messages, 3 authors, 2021-06-21
STALE1836d REVIEWED: 7 (6M)

[PATCH 12/16] block: define 'struct bvec_iter' as packed

From: Christoph Hellwig <hch@lst.de>
Date: 2021-06-15 13:14:34
Also in: linux-fsdevel, linux-nvme
Subsystem: the rest · Maintainer: Linus Torvalds

From: Ming Lei <redacted>

'struct bvec_iter' is embedded into 'struct bio', define it as packed
so that we can get one extra 4bytes for other uses without expanding
bio.

'struct bvec_iter' is often allocated on stack, so making it packed
doesn't affect performance. Also I have run io_uring on both
nvme/null_blk, and not observe performance effect in this way.

Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <redacted>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Mark Wunderlich <redacted>
---
 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 ff832e698efb..a0c4f41dfc83 100644
--- a/include/linux/bvec.h
+++ b/include/linux/bvec.h
@@ -43,7 +43,7 @@ struct bvec_iter {
 
 	unsigned int            bi_bvec_done;	/* number of bytes completed in
 						   current bvec */
-};
+} __packed;
 
 struct bvec_iter_all {
 	struct bio_vec	bv;
-- 
2.30.2
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