Please welcome ZFS - The last word in file systems.

ZFS file system was ported from OpenSolaris operating system. The code in under
CDDL license.

I'd like to thank all SUN developers that created this great piece of software.

Supported by:	Wheel LTD (http://www.wheel.pl/)
Supported by:	The FreeBSD Foundation (http://www.freebsdfoundation.org/)
Supported by:	Sentex (http://www.sentex.net/)

1 files changed, 394 insertions, 0 deletions

diff --git a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_cache.c b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_cache.c
new file mode 100644
index 0000000..b4fb960
--- /dev/null
+++ b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_cache.c
@@ -0,0 +1,394 @@
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or http://www.opensolaris.org/os/licensing.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+/*
+ * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
+ * Use is subject to license terms.
+ */
+
+#pragma ident	"%Z%%M%	%I%	%E% SMI"
+
+#include <sys/zfs_context.h>
+#include <sys/spa.h>
+#include <sys/vdev_impl.h>
+#include <sys/zio.h>
+
+/*
+ * Virtual device read-ahead caching.
+ *
+ * This file implements a simple LRU read-ahead cache.  When the DMU reads
+ * a given block, it will often want other, nearby blocks soon thereafter.
+ * We take advantage of this by reading a larger disk region and caching
+ * the result.  In the best case, this can turn 256 back-to-back 512-byte
+ * reads into a single 128k read followed by 255 cache hits; this reduces
+ * latency dramatically.  In the worst case, it can turn an isolated 512-byte
+ * read into a 128k read, which doesn't affect latency all that much but is
+ * terribly wasteful of bandwidth.  A more intelligent version of the cache
+ * could keep track of access patterns and not do read-ahead unless it sees
+ * at least two temporally close I/Os to the same region.  It could also
+ * take advantage of semantic information about the I/O.  And it could use
+ * something faster than an AVL tree; that was chosen solely for convenience.
+ *
+ * There are five cache operations: allocate, fill, read, write, evict.
+ *
+ * (1) Allocate.  This reserves a cache entry for the specified region.
+ *     We separate the allocate and fill operations so that multiple threads
+ *     don't generate I/O for the same cache miss.
+ *
+ * (2) Fill.  When the I/O for a cache miss completes, the fill routine
+ *     places the data in the previously allocated cache entry.
+ *
+ * (3) Read.  Read data from the cache.
+ *
+ * (4) Write.  Update cache contents after write completion.
+ *
+ * (5) Evict.  When allocating a new entry, we evict the oldest (LRU) entry
+ *     if the total cache size exceeds zfs_vdev_cache_size.
+ */
+
+/*
+ * These tunables are for performance analysis.
+ */
+/*
+ * All i/os smaller than zfs_vdev_cache_max will be turned into
+ * 1<<zfs_vdev_cache_bshift byte reads by the vdev_cache (aka software
+ * track buffer.  At most zfs_vdev_cache_size bytes will be kept in each
+ * vdev's vdev_cache.
+ */
+int zfs_vdev_cache_max = 1<<14;
+int zfs_vdev_cache_size = 10ULL << 20;
+int zfs_vdev_cache_bshift = 16;
+
+SYSCTL_DECL(_vfs_zfs_vdev);
+SYSCTL_NODE(_vfs_zfs_vdev, OID_AUTO, cache, CTLFLAG_RW, 0, "ZFS VDEV Cache");
+TUNABLE_INT("vfs.zfs.vdev.cache.max", &zfs_vdev_cache_max);
+SYSCTL_INT(_vfs_zfs_vdev_cache, OID_AUTO, max, CTLFLAG_RDTUN,
+    &zfs_vdev_cache_max, 0, "Maximum I/O request size that increase read size");
+TUNABLE_INT("vfs.zfs.vdev.cache.size", &zfs_vdev_cache_size);
+SYSCTL_INT(_vfs_zfs_vdev_cache, OID_AUTO, size, CTLFLAG_RDTUN,
+    &zfs_vdev_cache_size, 0, "Size of VDEV cache");
+
+#define	VCBS (1 << zfs_vdev_cache_bshift)
+
+static int
+vdev_cache_offset_compare(const void *a1, const void *a2)
+{
+	const vdev_cache_entry_t *ve1 = a1;
+	const vdev_cache_entry_t *ve2 = a2;
+
+	if (ve1->ve_offset < ve2->ve_offset)
+		return (-1);
+	if (ve1->ve_offset > ve2->ve_offset)
+		return (1);
+	return (0);
+}
+
+static int
+vdev_cache_lastused_compare(const void *a1, const void *a2)
+{
+	const vdev_cache_entry_t *ve1 = a1;
+	const vdev_cache_entry_t *ve2 = a2;
+
+	if (ve1->ve_lastused < ve2->ve_lastused)
+		return (-1);
+	if (ve1->ve_lastused > ve2->ve_lastused)
+		return (1);
+
+	/*
+	 * Among equally old entries, sort by offset to ensure uniqueness.
+	 */
+	return (vdev_cache_offset_compare(a1, a2));
+}
+
+/*
+ * Evict the specified entry from the cache.
+ */
+static void
+vdev_cache_evict(vdev_cache_t *vc, vdev_cache_entry_t *ve)
+{
+	ASSERT(MUTEX_HELD(&vc->vc_lock));
+	ASSERT(ve->ve_fill_io == NULL);
+	ASSERT(ve->ve_data != NULL);
+
+	dprintf("evicting %p, off %llx, LRU %llu, age %lu, hits %u, stale %u\n",
+	    vc, ve->ve_offset, ve->ve_lastused, lbolt - ve->ve_lastused,
+	    ve->ve_hits, ve->ve_missed_update);
+
+	avl_remove(&vc->vc_lastused_tree, ve);
+	avl_remove(&vc->vc_offset_tree, ve);
+	zio_buf_free(ve->ve_data, VCBS);
+	kmem_free(ve, sizeof (vdev_cache_entry_t));
+}
+
+/*
+ * Allocate an entry in the cache.  At the point we don't have the data,
+ * we're just creating a placeholder so that multiple threads don't all
+ * go off and read the same blocks.
+ */
+static vdev_cache_entry_t *
+vdev_cache_allocate(zio_t *zio)
+{
+	vdev_cache_t *vc = &zio->io_vd->vdev_cache;
+	uint64_t offset = P2ALIGN(zio->io_offset, VCBS);
+	vdev_cache_entry_t *ve;
+
+	ASSERT(MUTEX_HELD(&vc->vc_lock));
+
+	if (zfs_vdev_cache_size == 0)
+		return (NULL);
+
+	/*
+	 * If adding a new entry would exceed the cache size,
+	 * evict the oldest entry (LRU).
+	 */
+	if ((avl_numnodes(&vc->vc_lastused_tree) << zfs_vdev_cache_bshift) >
+	    zfs_vdev_cache_size) {
+		ve = avl_first(&vc->vc_lastused_tree);
+		if (ve->ve_fill_io != NULL) {
+			dprintf("can't evict in %p, still filling\n", vc);
+			return (NULL);
+		}
+		ASSERT(ve->ve_hits != 0);
+		vdev_cache_evict(vc, ve);
+	}
+
+	ve = kmem_zalloc(sizeof (vdev_cache_entry_t), KM_SLEEP);
+	ve->ve_offset = offset;
+	ve->ve_lastused = lbolt;
+	ve->ve_data = zio_buf_alloc(VCBS);
+
+	avl_add(&vc->vc_offset_tree, ve);
+	avl_add(&vc->vc_lastused_tree, ve);
+
+	return (ve);
+}
+
+static void
+vdev_cache_hit(vdev_cache_t *vc, vdev_cache_entry_t *ve, zio_t *zio)
+{
+	uint64_t cache_phase = P2PHASE(zio->io_offset, VCBS);
+
+	ASSERT(MUTEX_HELD(&vc->vc_lock));
+	ASSERT(ve->ve_fill_io == NULL);
+
+	if (ve->ve_lastused != lbolt) {
+		avl_remove(&vc->vc_lastused_tree, ve);
+		ve->ve_lastused = lbolt;
+		avl_add(&vc->vc_lastused_tree, ve);
+	}
+
+	ve->ve_hits++;
+	bcopy(ve->ve_data + cache_phase, zio->io_data, zio->io_size);
+}
+
+/*
+ * Fill a previously allocated cache entry with data.
+ */
+static void
+vdev_cache_fill(zio_t *zio)
+{
+	vdev_t *vd = zio->io_vd;
+	vdev_cache_t *vc = &vd->vdev_cache;
+	vdev_cache_entry_t *ve = zio->io_private;
+	zio_t *dio;
+
+	ASSERT(zio->io_size == VCBS);
+
+	/*
+	 * Add data to the cache.
+	 */
+	mutex_enter(&vc->vc_lock);
+
+	ASSERT(ve->ve_fill_io == zio);
+	ASSERT(ve->ve_offset == zio->io_offset);
+	ASSERT(ve->ve_data == zio->io_data);
+
+	ve->ve_fill_io = NULL;
+
+	/*
+	 * Even if this cache line was invalidated by a missed write update,
+	 * any reads that were queued up before the missed update are still
+	 * valid, so we can satisfy them from this line before we evict it.
+	 */
+	for (dio = zio->io_delegate_list; dio; dio = dio->io_delegate_next)
+		vdev_cache_hit(vc, ve, dio);
+
+	if (zio->io_error || ve->ve_missed_update)
+		vdev_cache_evict(vc, ve);
+
+	mutex_exit(&vc->vc_lock);
+
+	while ((dio = zio->io_delegate_list) != NULL) {
+		zio->io_delegate_list = dio->io_delegate_next;
+		dio->io_delegate_next = NULL;
+		dio->io_error = zio->io_error;
+		zio_next_stage(dio);
+	}
+}
+
+/*
+ * Read data from the cache.  Returns 0 on cache hit, errno on a miss.
+ */
+int
+vdev_cache_read(zio_t *zio)
+{
+	vdev_cache_t *vc = &zio->io_vd->vdev_cache;
+	vdev_cache_entry_t *ve, ve_search;
+	uint64_t cache_offset = P2ALIGN(zio->io_offset, VCBS);
+	uint64_t cache_phase = P2PHASE(zio->io_offset, VCBS);
+	zio_t *fio;
+
+	ASSERT(zio->io_type == ZIO_TYPE_READ);
+
+	if (zio->io_flags & ZIO_FLAG_DONT_CACHE)
+		return (EINVAL);
+
+	if (zio->io_size > zfs_vdev_cache_max)
+		return (EOVERFLOW);
+
+	/*
+	 * If the I/O straddles two or more cache blocks, don't cache it.
+	 */
+	if (P2CROSS(zio->io_offset, zio->io_offset + zio->io_size - 1, VCBS))
+		return (EXDEV);
+
+	ASSERT(cache_phase + zio->io_size <= VCBS);
+
+	mutex_enter(&vc->vc_lock);
+
+	ve_search.ve_offset = cache_offset;
+	ve = avl_find(&vc->vc_offset_tree, &ve_search, NULL);
+
+	if (ve != NULL) {
+		if (ve->ve_missed_update) {
+			mutex_exit(&vc->vc_lock);
+			return (ESTALE);
+		}
+
+		if ((fio = ve->ve_fill_io) != NULL) {
+			zio->io_delegate_next = fio->io_delegate_list;
+			fio->io_delegate_list = zio;
+			zio_vdev_io_bypass(zio);
+			mutex_exit(&vc->vc_lock);
+			return (0);
+		}
+
+		vdev_cache_hit(vc, ve, zio);
+		zio_vdev_io_bypass(zio);
+
+		mutex_exit(&vc->vc_lock);
+		zio_next_stage(zio);
+		return (0);
+	}
+
+	ve = vdev_cache_allocate(zio);
+
+	if (ve == NULL) {
+		mutex_exit(&vc->vc_lock);
+		return (ENOMEM);
+	}
+
+	fio = zio_vdev_child_io(zio, NULL, zio->io_vd, cache_offset,
+	    ve->ve_data, VCBS, ZIO_TYPE_READ, ZIO_PRIORITY_CACHE_FILL,
+	    ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_PROPAGATE |
+	    ZIO_FLAG_DONT_RETRY | ZIO_FLAG_NOBOOKMARK,
+	    vdev_cache_fill, ve);
+
+	ve->ve_fill_io = fio;
+	fio->io_delegate_list = zio;
+	zio_vdev_io_bypass(zio);
+
+	mutex_exit(&vc->vc_lock);
+	zio_nowait(fio);
+
+	return (0);
+}
+
+/*
+ * Update cache contents upon write completion.
+ */
+void
+vdev_cache_write(zio_t *zio)
+{
+	vdev_cache_t *vc = &zio->io_vd->vdev_cache;
+	vdev_cache_entry_t *ve, ve_search;
+	uint64_t io_start = zio->io_offset;
+	uint64_t io_end = io_start + zio->io_size;
+	uint64_t min_offset = P2ALIGN(io_start, VCBS);
+	uint64_t max_offset = P2ROUNDUP(io_end, VCBS);
+	avl_index_t where;
+
+	ASSERT(zio->io_type == ZIO_TYPE_WRITE);
+
+	mutex_enter(&vc->vc_lock);
+
+	ve_search.ve_offset = min_offset;
+	ve = avl_find(&vc->vc_offset_tree, &ve_search, &where);
+
+	if (ve == NULL)
+		ve = avl_nearest(&vc->vc_offset_tree, where, AVL_AFTER);
+
+	while (ve != NULL && ve->ve_offset < max_offset) {
+		uint64_t start = MAX(ve->ve_offset, io_start);
+		uint64_t end = MIN(ve->ve_offset + VCBS, io_end);
+
+		if (ve->ve_fill_io != NULL) {
+			ve->ve_missed_update = 1;
+		} else {
+			bcopy((char *)zio->io_data + start - io_start,
+			    ve->ve_data + start - ve->ve_offset, end - start);
+		}
+		ve = AVL_NEXT(&vc->vc_offset_tree, ve);
+	}
+	mutex_exit(&vc->vc_lock);
+}
+
+void
+vdev_cache_init(vdev_t *vd)
+{
+	vdev_cache_t *vc = &vd->vdev_cache;
+
+	mutex_init(&vc->vc_lock, NULL, MUTEX_DEFAULT, NULL);
+
+	avl_create(&vc->vc_offset_tree, vdev_cache_offset_compare,
+	    sizeof (vdev_cache_entry_t),
+	    offsetof(struct vdev_cache_entry, ve_offset_node));
+
+	avl_create(&vc->vc_lastused_tree, vdev_cache_lastused_compare,
+	    sizeof (vdev_cache_entry_t),
+	    offsetof(struct vdev_cache_entry, ve_lastused_node));
+}
+
+void
+vdev_cache_fini(vdev_t *vd)
+{
+	vdev_cache_t *vc = &vd->vdev_cache;
+	vdev_cache_entry_t *ve;
+
+	mutex_enter(&vc->vc_lock);
+	while ((ve = avl_first(&vc->vc_offset_tree)) != NULL)
+		vdev_cache_evict(vc, ve);
+	mutex_exit(&vc->vc_lock);
+
+	avl_destroy(&vc->vc_offset_tree);
+	avl_destroy(&vc->vc_lastused_tree);
+
+	mutex_destroy(&vc->vc_lock);
+}