From: Kent Overstreet <koverstreet@google.com>
Date: Tue, 4 Sep 2012 22:20:38 +0000 (-0700)
Subject: block: Change bio_split() to respect the current value of bi_idx
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=5b83636ae3c3b4f87d02a5929ad4dee831534db0;p=GitHub%2Fmt8127%2Fandroid_kernel_alcatel_ttab.git

block: Change bio_split() to respect the current value of bi_idx

In the current code bio_split() won't be seeing partially completed bios
so this doesn't change any behaviour, but this makes the code a bit
clearer as to what bio_split() actually requires.

The immediate purpose of the patch is removing unnecessary bi_idx
references, but the end goal is to allow partial completed bios to be
submitted, which along with immutable biovecs enables effecient bio
splitting.

Some of the callers were (double) checking that bios could be split, so
update their checks too.

Signed-off-by: Kent Overstreet <koverstreet@google.com>
CC: Jens Axboe <axboe@kernel.dk>
CC: Lars Ellenberg <drbd-dev@lists.linbit.com>
CC: Neil Brown <neilb@suse.de>
CC: Martin K. Petersen <martin.petersen@oracle.com>
---

diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
index 23a38afec351..fcf65e512cf5 100644
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -527,8 +527,7 @@ static void raid0_make_request(struct mddev *mddev, struct bio *bio)
 		sector_t sector = bio->bi_sector;
 		struct bio_pair *bp;
 		/* Sanity check -- queue functions should prevent this happening */
-		if ((bio->bi_vcnt != 1 && bio->bi_vcnt != 0) ||
-		    bio->bi_idx != 0)
+		if (bio_segments(bio) > 1)
 			goto bad_map;
 		/* This is a one page bio that upper layers
 		 * refuse to split for us, so we need to split it.
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 5ee14ab16a05..2e29df960bf5 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -1175,8 +1175,7 @@ static void make_request(struct mddev *mddev, struct bio * bio)
 			 || conf->prev.near_copies < conf->prev.raid_disks))) {
 		struct bio_pair *bp;
 		/* Sanity check -- queue functions should prevent this happening */
-		if ((bio->bi_vcnt != 1 && bio->bi_vcnt != 0) ||
-		    bio->bi_idx != 0)
+		if (bio_segments(bio) > 1)
 			goto bad_map;
 		/* This is a one page bio that upper layers
 		 * refuse to split for us, so we need to split it.
diff --git a/fs/bio-integrity.c b/fs/bio-integrity.c
index 8c4c604c840d..ca7b02dbf09d 100644
--- a/fs/bio-integrity.c
+++ b/fs/bio-integrity.c
@@ -661,8 +661,8 @@ void bio_integrity_split(struct bio *bio, struct bio_pair *bp, int sectors)
 	bp->bio1.bi_integrity = &bp->bip1;
 	bp->bio2.bi_integrity = &bp->bip2;
 
-	bp->iv1 = bip->bip_vec[0];
-	bp->iv2 = bip->bip_vec[0];
+	bp->iv1 = bip->bip_vec[bip->bip_idx];
+	bp->iv2 = bip->bip_vec[bip->bip_idx];
 
 	bp->bip1.bip_vec = &bp->iv1;
 	bp->bip2.bip_vec = &bp->iv2;
diff --git a/fs/bio.c b/fs/bio.c
index 7edc08d2246c..f1b4c1651089 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -1620,8 +1620,7 @@ struct bio_pair *bio_split(struct bio *bi, int first_sectors)
 	trace_block_split(bdev_get_queue(bi->bi_bdev), bi,
 				bi->bi_sector + first_sectors);
 
-	BUG_ON(bi->bi_vcnt != 1 && bi->bi_vcnt != 0);
-	BUG_ON(bi->bi_idx != 0);
+	BUG_ON(bio_segments(bi) > 1);
 	atomic_set(&bp->cnt, 3);
 	bp->error = 0;
 	bp->bio1 = *bi;
@@ -1631,8 +1630,8 @@ struct bio_pair *bio_split(struct bio *bi, int first_sectors)
 	bp->bio1.bi_size = first_sectors << 9;
 
 	if (bi->bi_vcnt != 0) {
-		bp->bv1 = bi->bi_io_vec[0];
-		bp->bv2 = bi->bi_io_vec[0];
+		bp->bv1 = *bio_iovec(bi);
+		bp->bv2 = *bio_iovec(bi);
 
 		if (bio_is_rw(bi)) {
 			bp->bv2.bv_offset += first_sectors << 9;