Author: mckusick
Date: Sat Feb 16 14:51:30 2013
New Revision: 246876
URL: http://svnweb.freebsd.org/changeset/base/246876
Log:
Add barrier write capability to the VFS buffer interface. A barrier
write is a disk write request that tells the disk that the buffer
being written must be committed to the media along with any writes
that preceeded it before any future blocks may be written to the drive.
Barrier writes are provided by adding the functions bbarrierwrite
(bwrite with barrier) and babarrierwrite (bawrite with barrier).
Following a bbarrierwrite the client knows that the requested buffer
is on the media. It does not ensure that buffers written before that
buffer are on the media. It only ensure that buffers written before
that buffer will get to the media before any buffers written after
that buffer. A flush command must be sent to the disk to ensure that
all earlier written buffers are on the media.
Reviewed by: kib
Tested by: Peter Holm
Modified:
head/sys/geom/geom_vfs.c
head/sys/kern/vfs_bio.c
head/sys/kern/vfs_cluster.c
head/sys/sys/buf.h
Modified: head/sys/geom/geom_vfs.c
==============================================================================
--- head/sys/geom/geom_vfs.c Sat Feb 16 12:52:40 2013 (r246875)
+++ head/sys/geom/geom_vfs.c Sat Feb 16 14:51:30 2013 (r246876)
@@ -192,6 +192,10 @@ g_vfs_strategy(struct bufobj *bo, struct
bip->bio_done = g_vfs_done;
bip->bio_caller2 = bp;
bip->bio_length = bp->b_bcount;
+ if (bp->b_flags & B_BARRIER) {
+ bip->bio_flags |= BIO_ORDERED;
+ bp->b_flags &= ~B_BARRIER;
+ }
g_io_request(bip, cp);
}
Modified: head/sys/kern/vfs_bio.c
==============================================================================
--- head/sys/kern/vfs_bio.c Sat Feb 16 12:52:40 2013 (r246875)
+++ head/sys/kern/vfs_bio.c Sat Feb 16 14:51:30 2013 (r246876)
@@ -206,6 +206,9 @@ SYSCTL_INT(_vfs, OID_AUTO, flushbufqtarg
static long notbufdflashes;
SYSCTL_LONG(_vfs, OID_AUTO, notbufdflashes, CTLFLAG_RD, ¬bufdflashes, 0,
"Number of dirty buffer flushes done by the bufdaemon helpers");
+static long barrierwrites;
+SYSCTL_LONG(_vfs, OID_AUTO, barrierwrites, CTLFLAG_RW, &barrierwrites, 0,
+ "Number of barrier writes");
/*
* Wakeup point for bufdaemon, as well as indicator of whether it is already
@@ -888,6 +891,9 @@ bufwrite(struct buf *bp)
return (0);
}
+ if (bp->b_flags & B_BARRIER)
+ barrierwrites++;
+
oldflags = bp->b_flags;
BUF_ASSERT_HELD(bp);
@@ -1007,6 +1013,8 @@ bdwrite(struct buf *bp)
CTR3(KTR_BUF, "bdwrite(%p) vp %p flags %X", bp, bp->b_vp, bp->b_flags);
KASSERT(bp->b_bufobj != NULL, ("No b_bufobj %p", bp));
+ KASSERT((bp->b_flags & B_BARRIER) == 0,
+ ("Barrier request in delayed write %p", bp));
BUF_ASSERT_HELD(bp);
if (bp->b_flags & B_INVAL) {
@@ -1167,6 +1175,40 @@ bawrite(struct buf *bp)
}
/*
+ * babarrierwrite:
+ *
+ * Asynchronous barrier write. Start output on a buffer, but do not
+ * wait for it to complete. Place a write barrier after this write so
+ * that this buffer and all buffers written before it are committed to
+ * the disk before any buffers written after this write are committed
+ * to the disk. The buffer is released when the output completes.
+ */
+void
+babarrierwrite(struct buf *bp)
+{
+
+ bp->b_flags |= B_ASYNC | B_BARRIER;
+ (void) bwrite(bp);
+}
+
+/*
+ * bbarrierwrite:
+ *
+ * Synchronous barrier write. Start output on a buffer and wait for
+ * it to complete. Place a write barrier after this write so that
+ * this buffer and all buffers written before it are committed to
+ * the disk before any buffers written after this write are committed
+ * to the disk. The buffer is released when the output completes.
+ */
+int
+bbarrierwrite(struct buf *bp)
+{
+
+ bp->b_flags |= B_BARRIER;
+ return (bwrite(bp));
+}
+
+/*
* bwillwrite:
*
* Called prior to the locking of any vnodes when we are expecting to
Modified: head/sys/kern/vfs_cluster.c
==============================================================================
--- head/sys/kern/vfs_cluster.c Sat Feb 16 12:52:40 2013 (r246875)
+++ head/sys/kern/vfs_cluster.c Sat Feb 16 14:51:30 2013 (r246876)
@@ -944,11 +944,17 @@ cluster_wbuild(vp, size, start_lbn, len)
}
bp->b_bcount += size;
bp->b_bufsize += size;
- bundirty(tbp);
- tbp->b_flags &= ~B_DONE;
- tbp->b_ioflags &= ~BIO_ERROR;
+ /*
+ * If any of the clustered buffers have their
+ * B_BARRIER flag set, transfer that request to
+ * the cluster.
+ */
+ bp->b_flags |= (tbp->b_flags & B_BARRIER);
+ tbp->b_flags &= ~(B_DONE | B_BARRIER);
tbp->b_flags |= B_ASYNC;
+ tbp->b_ioflags &= ~BIO_ERROR;
tbp->b_iocmd = BIO_WRITE;
+ bundirty(tbp);
reassignbuf(tbp); /* put on clean list */
bufobj_wref(tbp->b_bufobj);
BUF_KERNPROC(tbp);
Modified: head/sys/sys/buf.h
==============================================================================
--- head/sys/sys/buf.h Sat Feb 16 12:52:40 2013 (r246875)
+++ head/sys/sys/buf.h Sat Feb 16 14:51:30 2013 (r246876)
@@ -205,7 +205,7 @@ struct buf {
#define B_00000800 0x00000800 /* Available flag. */
#define B_00001000 0x00001000 /* Available flag. */
#define B_INVAL 0x00002000 /* Does not contain valid info.
*/
-#define B_00004000 0x00004000 /* Available flag. */
+#define B_BARRIER 0x00004000 /* Write this and all
preceeding first. */
#define B_NOCACHE 0x00008000 /* Do not cache block after
use. */
#define B_MALLOC 0x00010000 /* malloced b_data */
#define B_CLUSTEROK 0x00020000 /* Pagein op, so swap() can
count it. */
@@ -488,6 +488,8 @@ int breadn_flags(struct vnode *, daddr_t
void breada(struct vnode *, daddr_t *, int *, int, struct ucred *);
void bdwrite(struct buf *);
void bawrite(struct buf *);
+void babarrierwrite(struct buf *);
+int bbarrierwrite(struct buf *);
void bdirty(struct buf *);
void bundirty(struct buf *);
void bufstrategy(struct bufobj *, struct buf *);
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