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, 655 insertions, 0 deletions

diff --git a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_zfetch.c b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_zfetch.c
new file mode 100644
index 0000000..78d625c
--- /dev/null
+++ b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_zfetch.c
@@ -0,0 +1,655 @@
+/*
+ * 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/dnode.h>
+#include <sys/dmu_objset.h>
+#include <sys/dmu_zfetch.h>
+#include <sys/dmu.h>
+#include <sys/dbuf.h>
+
+/*
+ * I'm against tune-ables, but these should probably exist as tweakable globals
+ * until we can get this working the way we want it to.
+ */
+
+int zfs_prefetch_disable = 0;
+SYSCTL_DECL(_vfs_zfs);
+TUNABLE_INT("vfs.zfs.prefetch_disable", &zfs_prefetch_disable);
+SYSCTL_INT(_vfs_zfs, OID_AUTO, prefetch_disable, CTLFLAG_RDTUN,
+    &zfs_prefetch_disable, 0, "Disable prefetch");
+
+/* max # of streams per zfetch */
+uint32_t	zfetch_max_streams = 8;
+/* min time before stream reclaim */
+uint32_t	zfetch_min_sec_reap = 2;
+/* max number of blocks to fetch at a time */
+uint32_t	zfetch_block_cap = 256;
+/* number of bytes in a array_read at which we stop prefetching (1Mb) */
+uint64_t	zfetch_array_rd_sz = 1024 * 1024;
+
+/* forward decls for static routines */
+static int		dmu_zfetch_colinear(zfetch_t *, zstream_t *);
+static void		dmu_zfetch_dofetch(zfetch_t *, zstream_t *);
+static uint64_t		dmu_zfetch_fetch(dnode_t *, uint64_t, uint64_t);
+static uint64_t		dmu_zfetch_fetchsz(dnode_t *, uint64_t, uint64_t);
+static int		dmu_zfetch_find(zfetch_t *, zstream_t *, int);
+static int		dmu_zfetch_stream_insert(zfetch_t *, zstream_t *);
+static zstream_t	*dmu_zfetch_stream_reclaim(zfetch_t *);
+static void		dmu_zfetch_stream_remove(zfetch_t *, zstream_t *);
+static int		dmu_zfetch_streams_equal(zstream_t *, zstream_t *);
+
+/*
+ * Given a zfetch structure and a zstream structure, determine whether the
+ * blocks to be read are part of a co-linear pair of existing prefetch
+ * streams.  If a set is found, coalesce the streams, removing one, and
+ * configure the prefetch so it looks for a strided access pattern.
+ *
+ * In other words: if we find two sequential access streams that are
+ * the same length and distance N appart, and this read is N from the
+ * last stream, then we are probably in a strided access pattern.  So
+ * combine the two sequential streams into a single strided stream.
+ *
+ * If no co-linear streams are found, return NULL.
+ */
+static int
+dmu_zfetch_colinear(zfetch_t *zf, zstream_t *zh)
+{
+	zstream_t	*z_walk;
+	zstream_t	*z_comp;
+
+	if (! rw_tryenter(&zf->zf_rwlock, RW_WRITER))
+		return (0);
+
+	if (zh == NULL) {
+		rw_exit(&zf->zf_rwlock);
+		return (0);
+	}
+
+	for (z_walk = list_head(&zf->zf_stream); z_walk;
+	    z_walk = list_next(&zf->zf_stream, z_walk)) {
+		for (z_comp = list_next(&zf->zf_stream, z_walk); z_comp;
+		    z_comp = list_next(&zf->zf_stream, z_comp)) {
+			int64_t		diff;
+
+			if (z_walk->zst_len != z_walk->zst_stride ||
+			    z_comp->zst_len != z_comp->zst_stride) {
+				continue;
+			}
+
+			diff = z_comp->zst_offset - z_walk->zst_offset;
+			if (z_comp->zst_offset + diff == zh->zst_offset) {
+				z_walk->zst_offset = zh->zst_offset;
+				z_walk->zst_direction = diff < 0 ? -1 : 1;
+				z_walk->zst_stride =
+				    diff * z_walk->zst_direction;
+				z_walk->zst_ph_offset =
+				    zh->zst_offset + z_walk->zst_stride;
+				dmu_zfetch_stream_remove(zf, z_comp);
+				mutex_destroy(&z_comp->zst_lock);
+				kmem_free(z_comp, sizeof (zstream_t));
+
+				dmu_zfetch_dofetch(zf, z_walk);
+
+				rw_exit(&zf->zf_rwlock);
+				return (1);
+			}
+
+			diff = z_walk->zst_offset - z_comp->zst_offset;
+			if (z_walk->zst_offset + diff == zh->zst_offset) {
+				z_walk->zst_offset = zh->zst_offset;
+				z_walk->zst_direction = diff < 0 ? -1 : 1;
+				z_walk->zst_stride =
+				    diff * z_walk->zst_direction;
+				z_walk->zst_ph_offset =
+				    zh->zst_offset + z_walk->zst_stride;
+				dmu_zfetch_stream_remove(zf, z_comp);
+				mutex_destroy(&z_comp->zst_lock);
+				kmem_free(z_comp, sizeof (zstream_t));
+
+				dmu_zfetch_dofetch(zf, z_walk);
+
+				rw_exit(&zf->zf_rwlock);
+				return (1);
+			}
+		}
+	}
+
+	rw_exit(&zf->zf_rwlock);
+	return (0);
+}
+
+/*
+ * Given a zstream_t, determine the bounds of the prefetch.  Then call the
+ * routine that actually prefetches the individual blocks.
+ */
+static void
+dmu_zfetch_dofetch(zfetch_t *zf, zstream_t *zs)
+{
+	uint64_t	prefetch_tail;
+	uint64_t	prefetch_limit;
+	uint64_t	prefetch_ofst;
+	uint64_t	prefetch_len;
+	uint64_t	blocks_fetched;
+
+	zs->zst_stride = MAX((int64_t)zs->zst_stride, zs->zst_len);
+	zs->zst_cap = MIN(zfetch_block_cap, 2 * zs->zst_cap);
+
+	prefetch_tail = MAX((int64_t)zs->zst_ph_offset,
+	    (int64_t)(zs->zst_offset + zs->zst_stride));
+	/*
+	 * XXX: use a faster division method?
+	 */
+	prefetch_limit = zs->zst_offset + zs->zst_len +
+	    (zs->zst_cap * zs->zst_stride) / zs->zst_len;
+
+	while (prefetch_tail < prefetch_limit) {
+		prefetch_ofst = zs->zst_offset + zs->zst_direction *
+		    (prefetch_tail - zs->zst_offset);
+
+		prefetch_len = zs->zst_len;
+
+		/*
+		 * Don't prefetch beyond the end of the file, if working
+		 * backwards.
+		 */
+		if ((zs->zst_direction == ZFETCH_BACKWARD) &&
+		    (prefetch_ofst > prefetch_tail)) {
+			prefetch_len += prefetch_ofst;
+			prefetch_ofst = 0;
+		}
+
+		/* don't prefetch more than we're supposed to */
+		if (prefetch_len > zs->zst_len)
+			break;
+
+		blocks_fetched = dmu_zfetch_fetch(zf->zf_dnode,
+		    prefetch_ofst, zs->zst_len);
+
+		prefetch_tail += zs->zst_stride;
+		/* stop if we've run out of stuff to prefetch */
+		if (blocks_fetched < zs->zst_len)
+			break;
+	}
+	zs->zst_ph_offset = prefetch_tail;
+	zs->zst_last = lbolt;
+}
+
+/*
+ * This takes a pointer to a zfetch structure and a dnode.  It performs the
+ * necessary setup for the zfetch structure, grokking data from the
+ * associated dnode.
+ */
+void
+dmu_zfetch_init(zfetch_t *zf, dnode_t *dno)
+{
+	if (zf == NULL) {
+		return;
+	}
+
+	zf->zf_dnode = dno;
+	zf->zf_stream_cnt = 0;
+	zf->zf_alloc_fail = 0;
+
+	list_create(&zf->zf_stream, sizeof (zstream_t),
+	    offsetof(zstream_t, zst_node));
+
+	rw_init(&zf->zf_rwlock, NULL, RW_DEFAULT, NULL);
+}
+
+/*
+ * This function computes the actual size, in blocks, that can be prefetched,
+ * and fetches it.
+ */
+static uint64_t
+dmu_zfetch_fetch(dnode_t *dn, uint64_t blkid, uint64_t nblks)
+{
+	uint64_t	fetchsz;
+	uint64_t	i;
+
+	fetchsz = dmu_zfetch_fetchsz(dn, blkid, nblks);
+
+	for (i = 0; i < fetchsz; i++) {
+		dbuf_prefetch(dn, blkid + i);
+	}
+
+	return (fetchsz);
+}
+
+/*
+ * this function returns the number of blocks that would be prefetched, based
+ * upon the supplied dnode, blockid, and nblks.  This is used so that we can
+ * update streams in place, and then prefetch with their old value after the
+ * fact.  This way, we can delay the prefetch, but subsequent accesses to the
+ * stream won't result in the same data being prefetched multiple times.
+ */
+static uint64_t
+dmu_zfetch_fetchsz(dnode_t *dn, uint64_t blkid, uint64_t nblks)
+{
+	uint64_t	fetchsz;
+
+	if (blkid > dn->dn_maxblkid) {
+		return (0);
+	}
+
+	/* compute fetch size */
+	if (blkid + nblks + 1 > dn->dn_maxblkid) {
+		fetchsz = (dn->dn_maxblkid - blkid) + 1;
+		ASSERT(blkid + fetchsz - 1 <= dn->dn_maxblkid);
+	} else {
+		fetchsz = nblks;
+	}
+
+
+	return (fetchsz);
+}
+
+/*
+ * given a zfetch and a zsearch structure, see if there is an associated zstream
+ * for this block read.  If so, it starts a prefetch for the stream it
+ * located and returns true, otherwise it returns false
+ */
+static int
+dmu_zfetch_find(zfetch_t *zf, zstream_t *zh, int prefetched)
+{
+	zstream_t	*zs;
+	int64_t		diff;
+	int		reset = !prefetched;
+	int		rc = 0;
+
+	if (zh == NULL)
+		return (0);
+
+	/*
+	 * XXX: This locking strategy is a bit coarse; however, it's impact has
+	 * yet to be tested.  If this turns out to be an issue, it can be
+	 * modified in a number of different ways.
+	 */
+
+	rw_enter(&zf->zf_rwlock, RW_READER);
+top:
+
+	for (zs = list_head(&zf->zf_stream); zs;
+	    zs = list_next(&zf->zf_stream, zs)) {
+
+		/*
+		 * XXX - should this be an assert?
+		 */
+		if (zs->zst_len == 0) {
+			/* bogus stream */
+			continue;
+		}
+
+		/*
+		 * We hit this case when we are in a strided prefetch stream:
+		 * we will read "len" blocks before "striding".
+		 */
+		if (zh->zst_offset >= zs->zst_offset &&
+		    zh->zst_offset < zs->zst_offset + zs->zst_len) {
+			/* already fetched */
+			rc = 1;
+			goto out;
+		}
+
+		/*
+		 * This is the forward sequential read case: we increment
+		 * len by one each time we hit here, so we will enter this
+		 * case on every read.
+		 */
+		if (zh->zst_offset == zs->zst_offset + zs->zst_len) {
+
+			reset = !prefetched && zs->zst_len > 1;
+
+			mutex_enter(&zs->zst_lock);
+
+			if (zh->zst_offset != zs->zst_offset + zs->zst_len) {
+				mutex_exit(&zs->zst_lock);
+				goto top;
+			}
+			zs->zst_len += zh->zst_len;
+			diff = zs->zst_len - zfetch_block_cap;
+			if (diff > 0) {
+				zs->zst_offset += diff;
+				zs->zst_len = zs->zst_len > diff ?
+				    zs->zst_len - diff : 0;
+			}
+			zs->zst_direction = ZFETCH_FORWARD;
+
+			break;
+
+		/*
+		 * Same as above, but reading backwards through the file.
+		 */
+		} else if (zh->zst_offset == zs->zst_offset - zh->zst_len) {
+			/* backwards sequential access */
+
+			reset = !prefetched && zs->zst_len > 1;
+
+			mutex_enter(&zs->zst_lock);
+
+			if (zh->zst_offset != zs->zst_offset - zh->zst_len) {
+				mutex_exit(&zs->zst_lock);
+				goto top;
+			}
+
+			zs->zst_offset = zs->zst_offset > zh->zst_len ?
+			    zs->zst_offset - zh->zst_len : 0;
+			zs->zst_ph_offset = zs->zst_ph_offset > zh->zst_len ?
+			    zs->zst_ph_offset - zh->zst_len : 0;
+			zs->zst_len += zh->zst_len;
+
+			diff = zs->zst_len - zfetch_block_cap;
+			if (diff > 0) {
+				zs->zst_ph_offset = zs->zst_ph_offset > diff ?
+				    zs->zst_ph_offset - diff : 0;
+				zs->zst_len = zs->zst_len > diff ?
+				    zs->zst_len - diff : zs->zst_len;
+			}
+			zs->zst_direction = ZFETCH_BACKWARD;
+
+			break;
+
+		} else if ((zh->zst_offset - zs->zst_offset - zs->zst_stride <
+		    zs->zst_len) && (zs->zst_len != zs->zst_stride)) {
+			/* strided forward access */
+
+			mutex_enter(&zs->zst_lock);
+
+			if ((zh->zst_offset - zs->zst_offset - zs->zst_stride >=
+			    zs->zst_len) || (zs->zst_len == zs->zst_stride)) {
+				mutex_exit(&zs->zst_lock);
+				goto top;
+			}
+
+			zs->zst_offset += zs->zst_stride;
+			zs->zst_direction = ZFETCH_FORWARD;
+
+			break;
+
+		} else if ((zh->zst_offset - zs->zst_offset + zs->zst_stride <
+		    zs->zst_len) && (zs->zst_len != zs->zst_stride)) {
+			/* strided reverse access */
+
+			mutex_enter(&zs->zst_lock);
+
+			if ((zh->zst_offset - zs->zst_offset + zs->zst_stride >=
+			    zs->zst_len) || (zs->zst_len == zs->zst_stride)) {
+				mutex_exit(&zs->zst_lock);
+				goto top;
+			}
+
+			zs->zst_offset = zs->zst_offset > zs->zst_stride ?
+			    zs->zst_offset - zs->zst_stride : 0;
+			zs->zst_ph_offset = (zs->zst_ph_offset >
+			    (2 * zs->zst_stride)) ?
+			    (zs->zst_ph_offset - (2 * zs->zst_stride)) : 0;
+			zs->zst_direction = ZFETCH_BACKWARD;
+
+			break;
+		}
+	}
+
+	if (zs) {
+		if (reset) {
+			zstream_t *remove = zs;
+
+			rc = 0;
+			mutex_exit(&zs->zst_lock);
+			rw_exit(&zf->zf_rwlock);
+			rw_enter(&zf->zf_rwlock, RW_WRITER);
+			/*
+			 * Relocate the stream, in case someone removes
+			 * it while we were acquiring the WRITER lock.
+			 */
+			for (zs = list_head(&zf->zf_stream); zs;
+			    zs = list_next(&zf->zf_stream, zs)) {
+				if (zs == remove) {
+					dmu_zfetch_stream_remove(zf, zs);
+					mutex_destroy(&zs->zst_lock);
+					kmem_free(zs, sizeof (zstream_t));
+					break;
+				}
+			}
+		} else {
+			rc = 1;
+			dmu_zfetch_dofetch(zf, zs);
+			mutex_exit(&zs->zst_lock);
+		}
+	}
+out:
+	rw_exit(&zf->zf_rwlock);
+	return (rc);
+}
+
+/*
+ * Clean-up state associated with a zfetch structure.  This frees allocated
+ * structure members, empties the zf_stream tree, and generally makes things
+ * nice.  This doesn't free the zfetch_t itself, that's left to the caller.
+ */
+void
+dmu_zfetch_rele(zfetch_t *zf)
+{
+	zstream_t	*zs;
+	zstream_t	*zs_next;
+
+	ASSERT(!RW_LOCK_HELD(&zf->zf_rwlock));
+
+	for (zs = list_head(&zf->zf_stream); zs; zs = zs_next) {
+		zs_next = list_next(&zf->zf_stream, zs);
+
+		list_remove(&zf->zf_stream, zs);
+		mutex_destroy(&zs->zst_lock);
+		kmem_free(zs, sizeof (zstream_t));
+	}
+	list_destroy(&zf->zf_stream);
+	rw_destroy(&zf->zf_rwlock);
+
+	zf->zf_dnode = NULL;
+}
+
+/*
+ * Given a zfetch and zstream structure, insert the zstream structure into the
+ * AVL tree contained within the zfetch structure.  Peform the appropriate
+ * book-keeping.  It is possible that another thread has inserted a stream which
+ * matches one that we are about to insert, so we must be sure to check for this
+ * case.  If one is found, return failure, and let the caller cleanup the
+ * duplicates.
+ */
+static int
+dmu_zfetch_stream_insert(zfetch_t *zf, zstream_t *zs)
+{
+	zstream_t	*zs_walk;
+	zstream_t	*zs_next;
+
+	ASSERT(RW_WRITE_HELD(&zf->zf_rwlock));
+
+	for (zs_walk = list_head(&zf->zf_stream); zs_walk; zs_walk = zs_next) {
+		zs_next = list_next(&zf->zf_stream, zs_walk);
+
+		if (dmu_zfetch_streams_equal(zs_walk, zs)) {
+		    return (0);
+		}
+	}
+
+	list_insert_head(&zf->zf_stream, zs);
+	zf->zf_stream_cnt++;
+
+	return (1);
+}
+
+
+/*
+ * Walk the list of zstreams in the given zfetch, find an old one (by time), and
+ * reclaim it for use by the caller.
+ */
+static zstream_t *
+dmu_zfetch_stream_reclaim(zfetch_t *zf)
+{
+	zstream_t	*zs;
+
+	if (! rw_tryenter(&zf->zf_rwlock, RW_WRITER))
+		return (0);
+
+	for (zs = list_head(&zf->zf_stream); zs;
+	    zs = list_next(&zf->zf_stream, zs)) {
+
+		if (((lbolt - zs->zst_last) / hz) > zfetch_min_sec_reap)
+			break;
+	}
+
+	if (zs) {
+		dmu_zfetch_stream_remove(zf, zs);
+		mutex_destroy(&zs->zst_lock);
+		bzero(zs, sizeof (zstream_t));
+	} else {
+		zf->zf_alloc_fail++;
+	}
+	rw_exit(&zf->zf_rwlock);
+
+	return (zs);
+}
+
+/*
+ * Given a zfetch and zstream structure, remove the zstream structure from its
+ * container in the zfetch structure.  Perform the appropriate book-keeping.
+ */
+static void
+dmu_zfetch_stream_remove(zfetch_t *zf, zstream_t *zs)
+{
+	ASSERT(RW_WRITE_HELD(&zf->zf_rwlock));
+
+	list_remove(&zf->zf_stream, zs);
+	zf->zf_stream_cnt--;
+}
+
+static int
+dmu_zfetch_streams_equal(zstream_t *zs1, zstream_t *zs2)
+{
+	if (zs1->zst_offset != zs2->zst_offset)
+		return (0);
+
+	if (zs1->zst_len != zs2->zst_len)
+		return (0);
+
+	if (zs1->zst_stride != zs2->zst_stride)
+		return (0);
+
+	if (zs1->zst_ph_offset != zs2->zst_ph_offset)
+		return (0);
+
+	if (zs1->zst_cap != zs2->zst_cap)
+		return (0);
+
+	if (zs1->zst_direction != zs2->zst_direction)
+		return (0);
+
+	return (1);
+}
+
+/*
+ * This is the prefetch entry point.  It calls all of the other dmu_zfetch
+ * routines to create, delete, find, or operate upon prefetch streams.
+ */
+void
+dmu_zfetch(zfetch_t *zf, uint64_t offset, uint64_t size, int prefetched)
+{
+	zstream_t	zst;
+	zstream_t	*newstream;
+	int		fetched;
+	int		inserted;
+	unsigned int	blkshft;
+	uint64_t	blksz;
+
+	if (zfs_prefetch_disable)
+		return;
+
+	/* files that aren't ln2 blocksz are only one block -- nothing to do */
+	if (!zf->zf_dnode->dn_datablkshift)
+		return;
+
+	/* convert offset and size, into blockid and nblocks */
+	blkshft = zf->zf_dnode->dn_datablkshift;
+	blksz = (1 << blkshft);
+
+	bzero(&zst, sizeof (zstream_t));
+	zst.zst_offset = offset >> blkshft;
+	zst.zst_len = (P2ROUNDUP(offset + size, blksz) -
+	    P2ALIGN(offset, blksz)) >> blkshft;
+
+	fetched = dmu_zfetch_find(zf, &zst, prefetched);
+	if (!fetched) {
+		fetched = dmu_zfetch_colinear(zf, &zst);
+	}
+
+	if (!fetched) {
+		newstream = dmu_zfetch_stream_reclaim(zf);
+
+		/*
+		 * we still couldn't find a stream, drop the lock, and allocate
+		 * one if possible.  Otherwise, give up and go home.
+		 */
+		if (newstream == NULL) {
+			uint64_t	maxblocks;
+			uint32_t	max_streams;
+			uint32_t	cur_streams;
+
+			cur_streams = zf->zf_stream_cnt;
+			maxblocks = zf->zf_dnode->dn_maxblkid;
+
+			max_streams = MIN(zfetch_max_streams,
+			    (maxblocks / zfetch_block_cap));
+			if (max_streams == 0) {
+				max_streams++;
+			}
+
+			if (cur_streams >= max_streams) {
+				return;
+			}
+
+			newstream = kmem_zalloc(sizeof (zstream_t), KM_SLEEP);
+		}
+
+		newstream->zst_offset = zst.zst_offset;
+		newstream->zst_len = zst.zst_len;
+		newstream->zst_stride = zst.zst_len;
+		newstream->zst_ph_offset = zst.zst_len + zst.zst_offset;
+		newstream->zst_cap = zst.zst_len;
+		newstream->zst_direction = ZFETCH_FORWARD;
+		newstream->zst_last = lbolt;
+
+		mutex_init(&newstream->zst_lock, NULL, MUTEX_DEFAULT, NULL);
+
+		rw_enter(&zf->zf_rwlock, RW_WRITER);
+		inserted = dmu_zfetch_stream_insert(zf, newstream);
+		rw_exit(&zf->zf_rwlock);
+
+		if (!inserted) {
+			mutex_destroy(&newstream->zst_lock);
+			kmem_free(newstream, sizeof (zstream_t));
+		}
+	}
+}