From 079f2df393209d4eb295abb686e372ce01b9186a Mon Sep 17 00:00:00 2001
From: Poul-Henning Kamp <phk@FreeBSD.org>
Date: Sun, 6 May 2001 21:55:22 +0000
Subject: [PATCH] Make the disk mini-layer check for and handle zero-length
 transfers instead of the underlying drivers.

---
 sys/dev/aac/aac_disk.c    | 7 -------
 sys/dev/amr/amr_disk.c    | 4 ----
 sys/dev/ata/ata-disk.c    | 7 -------
 sys/dev/ata/ata-raid.c    | 7 -------
 sys/dev/ata/atapi-fd.c    | 7 -------
 sys/dev/ida/ida_disk.c    | 6 ------
 sys/dev/mlx/mlx_disk.c    | 4 ----
 sys/dev/twe/twe_freebsd.c | 8 --------
 sys/kern/subr_disk.c      | 6 ++++++
 9 files changed, 6 insertions(+), 50 deletions(-)

diff --git a/sys/dev/aac/aac_disk.c b/sys/dev/aac/aac_disk.c
index 09bd9716445b..564f79e42bf2 100644
--- a/sys/dev/aac/aac_disk.c
+++ b/sys/dev/aac/aac_disk.c
@@ -168,13 +168,6 @@ aac_disk_strategy(struct bio *bp)
 	return;
     }
 
-    /* do-nothing operation? */
-    if (bp->bio_bcount == 0) {
-	bp->bio_resid = bp->bio_bcount;
-	biodone(bp);
-	return;
-    }
-
     /* perform accounting */
     devstat_start_transaction(&sc->ad_stats);
 
diff --git a/sys/dev/amr/amr_disk.c b/sys/dev/amr/amr_disk.c
index f846043bbc97..de703fe03dda 100644
--- a/sys/dev/amr/amr_disk.c
+++ b/sys/dev/amr/amr_disk.c
@@ -165,10 +165,6 @@ amrd_strategy(struct bio *bio)
 	goto bad;
     }
 
-    /* do-nothing operation */
-    if (bio->bio_bcount == 0)
-	goto done;
-
     devstat_start_transaction(&sc->amrd_stats);
     amr_submit_bio(sc->amrd_controller, bio);
     return;
diff --git a/sys/dev/ata/ata-disk.c b/sys/dev/ata/ata-disk.c
index 6d449582fa74..d4a2b9c0831a 100644
--- a/sys/dev/ata/ata-disk.c
+++ b/sys/dev/ata/ata-disk.c
@@ -269,13 +269,6 @@ adstrategy(struct bio *bp)
 	return;
     }
 
-    /* if it's a null transfer, return immediatly. */
-    if (bp->bio_bcount == 0) {
-	bp->bio_resid = 0;
-	biodone(bp);
-	return;
-    }
-
     s = splbio();
     bioqdisksort(&adp->queue, bp);
     ata_start(adp->controller);
diff --git a/sys/dev/ata/ata-raid.c b/sys/dev/ata/ata-raid.c
index 30cbd7643342..546b9986f8d1 100644
--- a/sys/dev/ata/ata-raid.c
+++ b/sys/dev/ata/ata-raid.c
@@ -158,13 +158,6 @@ arstrategy(struct bio *bp)
     int lba, count, chunk;
     caddr_t data;
 
-    /* if it's a null transfer, return immediatly. */
-    if (bp->bio_bcount == 0) {
-	bp->bio_resid = 0;
-	biodone(bp);
-	return;
-    }
-
     bp->bio_resid = bp->bio_bcount;
     lba = bp->bio_pblkno;
     data = bp->bio_data;
diff --git a/sys/dev/ata/atapi-fd.c b/sys/dev/ata/atapi-fd.c
index a831ff409e7d..a419d2b1353d 100644
--- a/sys/dev/ata/atapi-fd.c
+++ b/sys/dev/ata/atapi-fd.c
@@ -307,13 +307,6 @@ afdstrategy(struct bio *bp)
 	return;
     }
 
-    /* if it's a null transfer, return immediatly. */
-    if (bp->bio_bcount == 0) {
-	bp->bio_resid = 0;
-	biodone(bp);
-	return;
-    }
-
     s = splbio();
     bioqdisksort(&fdp->queue, bp);
     ata_start(fdp->atp->controller);
diff --git a/sys/dev/ida/ida_disk.c b/sys/dev/ida/ida_disk.c
index 99251efc8232..4bf662c25786 100644
--- a/sys/dev/ida/ida_disk.c
+++ b/sys/dev/ida/ida_disk.c
@@ -169,12 +169,6 @@ idad_strategy(struct bio *bp)
 		goto bad;
 	}
 
-	/*
-	 * If it's a null transfer, return immediately
-	 */
-	if (bp->bio_bcount == 0)
-		goto done;
-
 	bp->bio_driver1 = drv;
 	s = splbio();
 	devstat_start_transaction(&drv->stats);
diff --git a/sys/dev/mlx/mlx_disk.c b/sys/dev/mlx/mlx_disk.c
index 18698c2cffd8..b372247d313e 100644
--- a/sys/dev/mlx/mlx_disk.c
+++ b/sys/dev/mlx/mlx_disk.c
@@ -179,10 +179,6 @@ mlxd_strategy(struct bio *bp)
 	goto bad;
     }
 
-    /* do-nothing operation */
-    if (bp->bio_bcount == 0)
-	goto done;
-
     devstat_start_transaction(&sc->mlxd_stats);
     mlx_submit_buf(sc->mlxd_controller, bp);
     return;
diff --git a/sys/dev/twe/twe_freebsd.c b/sys/dev/twe/twe_freebsd.c
index 15c55744be21..677e7af82a33 100644
--- a/sys/dev/twe/twe_freebsd.c
+++ b/sys/dev/twe/twe_freebsd.c
@@ -668,14 +668,6 @@ twed_strategy(twe_bio *bp)
 	return;
     }
 
-    /* do-nothing operation? */
-    if (TWE_BIO_LENGTH(bp) == 0) {
-	TWE_BIO_RESID(bp) = 0;
-	TWE_BIO_DONE(bp);
-	TWED_BIO_OUT;
-	return;
-    }
-
     /* perform accounting */
     TWE_BIO_STATS_START(bp);
 
diff --git a/sys/kern/subr_disk.c b/sys/kern/subr_disk.c
index b4932cbf766e..aaa28c8dac6e 100644
--- a/sys/kern/subr_disk.c
+++ b/sys/kern/subr_disk.c
@@ -309,6 +309,12 @@ diskstrategy(struct bio *bp)
 		return;
 	}
 
+	if (bp->bio_bcount == 0) {
+		bp->bio_resid = 0;
+		biodone(bp);
+		return;
+	}
+
 	KASSERT(dp->d_devsw != NULL, ("NULL devsw"));
 	KASSERT(dp->d_devsw->d_strategy != NULL, ("NULL d_strategy"));
 	dp->d_devsw->d_strategy(bp);