From: Ming Lei <ming.lei@redhat.com>
Date: Tue, 12 Oct 2021 11:12:23 +0000 (+0200)
Subject: block: define 'struct bvec_iter' as packed
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=19416123ab3e1348b3532347af221d8f60838431;p=linux.git

block: define 'struct bvec_iter' as packed

'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 <ming.lei@redhat.com>
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 <mark.wunderlich@intel.com>
Link: https://lore.kernel.org/r/20211012111226.760968-14-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---

diff --git a/include/linux/bvec.h b/include/linux/bvec.h
index 0e9bdd42dafb6..35c25dff651a5 100644
--- a/include/linux/bvec.h
+++ b/include/linux/bvec.h
@@ -44,7 +44,7 @@ struct bvec_iter {
 
 	unsigned int            bi_bvec_done;	/* number of bytes completed in
 						   current bvec */
-};
+} __packed;
 
 struct bvec_iter_all {
 	struct bio_vec	bv;