From: Ming Lei <ming.lei@redhat.com>
Date: Thu, 22 Apr 2021 12:20:28 +0000 (+0800)
Subject: block: define 'struct bvec_iter' as packed
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=999177480c34efbaf3d60ad59c9982d0498dde11;p=users%2Fhch%2Fblock.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>
---

diff --git a/include/linux/bvec.h b/include/linux/bvec.h
index 0e9bdd42dafb..35c25dff651a 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;