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Date:      Thu, 10 Oct 2013 18:34:46 +0000 (UTC)
From:      Alexander Motin <mav@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-projects@freebsd.org
Subject:   svn commit: r256286 - projects/camlock/sys/geom
Message-ID:  <201310101834.r9AIYk6N092930@svn.freebsd.org>
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Author: mav
Date: Thu Oct 10 18:34:46 2013
New Revision: 256286
URL: http://svnweb.freebsd.org/changeset/base/256286

Log:
  Avoid BIO clonning (memory allocation) inside GEOM DISK when request is
  within maximal allowed size and so it is not going to be splitted.
  
  In such case the only conflicting field in struct bio is bio_done.  So,
  instead of allocating whole new struct bio for that only field, copy that
  field into bio_to, that is GEOM-specific and should not be used by disk
  drivers below.  On request completion reconstruct original bio_done field
  from bio_to and original bio_to field from bio_disk.

Modified:
  projects/camlock/sys/geom/geom_disk.c

Modified: projects/camlock/sys/geom/geom_disk.c
==============================================================================
--- projects/camlock/sys/geom/geom_disk.c	Thu Oct 10 18:18:04 2013	(r256285)
+++ projects/camlock/sys/geom/geom_disk.c	Thu Oct 10 18:34:46 2013	(r256286)
@@ -256,6 +256,25 @@ g_disk_done(struct bio *bp)
 	g_destroy_bio(bp);
 }
 
+static void
+g_disk_done_single(struct bio *bp)
+{
+	struct bintime now;
+	struct g_disk_softc *sc;
+
+	bp->bio_completed = bp->bio_length - bp->bio_resid;
+	bp->bio_done = (void *)bp->bio_to;
+	bp->bio_to = LIST_FIRST(&bp->bio_disk->d_geom->provider);
+	if ((bp->bio_cmd & (BIO_READ|BIO_WRITE|BIO_DELETE)) != 0) {
+		binuptime(&now);
+		sc = bp->bio_to->private;
+		mtx_lock(&sc->done_mtx);
+		devstat_end_transaction_bio_bt(sc->dp->d_devstat, bp, &now);
+		mtx_unlock(&sc->done_mtx);
+	}
+	g_io_deliver(bp, bp->bio_error);
+}
+
 static int
 g_disk_ioctl(struct g_provider *pp, u_long cmd, void * data, int fflag, struct thread *td)
 {
@@ -281,7 +300,7 @@ g_disk_start(struct bio *bp)
 	struct disk *dp;
 	struct g_disk_softc *sc;
 	int error;
-	off_t off;
+	off_t d_maxsize, off;
 
 	sc = bp->bio_to->private;
 	if (sc == NULL || (dp = sc->dp) == NULL || dp->d_destroyed) {
@@ -298,6 +317,22 @@ g_disk_start(struct bio *bp)
 		/* fall-through */
 	case BIO_READ:
 	case BIO_WRITE:
+		d_maxsize = (bp->bio_cmd == BIO_DELETE) ?
+		    dp->d_delmaxsize : dp->d_maxsize;
+		if (bp->bio_length <= d_maxsize) {
+			bp->bio_disk = dp;
+			bp->bio_to = (void *)bp->bio_done;
+			bp->bio_done = g_disk_done_single;
+			bp->bio_pblkno = bp->bio_offset / dp->d_sectorsize;
+			bp->bio_bcount = bp->bio_length;
+			mtx_lock(&sc->start_mtx);
+			devstat_start_transaction_bio(dp->d_devstat, bp);
+			mtx_unlock(&sc->start_mtx);
+			g_disk_lock_giant(dp);
+			dp->d_strategy(bp);
+			g_disk_unlock_giant(dp);
+			break;
+		}
 		off = 0;
 		bp3 = NULL;
 		bp2 = g_clone_bio(bp);
@@ -306,10 +341,6 @@ g_disk_start(struct bio *bp)
 			break;
 		}
 		do {
-			off_t d_maxsize;
-
-			d_maxsize = (bp->bio_cmd == BIO_DELETE) ?
-			    dp->d_delmaxsize : dp->d_maxsize;
 			bp2->bio_offset += off;
 			bp2->bio_length -= off;
 			if ((bp->bio_flags & BIO_UNMAPPED) == 0) {
@@ -408,15 +439,11 @@ g_disk_start(struct bio *bp)
 			error = EOPNOTSUPP;
 			break;
 		}
-		bp2 = g_clone_bio(bp);
-		if (bp2 == NULL) {
-			g_io_deliver(bp, ENOMEM);
-			return;
-		}
-		bp2->bio_done = g_disk_done;
-		bp2->bio_disk = dp;
+		bp->bio_disk = dp;
+		bp->bio_to = (void *)bp->bio_done;
+		bp->bio_done = g_disk_done_single;
 		g_disk_lock_giant(dp);
-		dp->d_strategy(bp2);
+		dp->d_strategy(bp);
 		g_disk_unlock_giant(dp);
 		break;
 	default:

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