brt: lift internal definitions into _impl header

So that zdb (and others!) can get at the BRT on-disk structures.

Reviewed-by: Alexander Motin <[email protected]>
Reviewed-by: Kay Pedersen <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Rob Norris <[email protected]>
Closes #15541

2 files changed, 200 insertions, 0 deletions

diff --git a/include/Makefile.am b/include/Makefile.am
index 569de6dfa..5f38f6ac6 100644
--- a/include/Makefile.am
+++ b/include/Makefile.am
@@ -33,6 +33,7 @@ COMMON_H = \
 	sys/bqueue.h \
 	sys/btree.h \
 	sys/brt.h \
+	sys/brt_impl.h \
 	sys/dataset_kstats.h \
 	sys/dbuf.h \
 	sys/ddt.h \
diff --git a/include/sys/brt_impl.h b/include/sys/brt_impl.h
new file mode 100644
index 000000000..9cc06fbb2
--- /dev/null
+++ b/include/sys/brt_impl.h
@@ -0,0 +1,199 @@
+/*
+ * 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 https://opensource.org/licenses/CDDL-1.0.
+ * 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 (c) 2020, 2021, 2022 by Pawel Jakub Dawidek
+ */
+
+#ifndef _SYS_BRT_IMPL_H
+#define	_SYS_BRT_IMPL_H
+
+#ifdef	__cplusplus
+extern "C" {
+#endif
+
+/*
+ * BRT - Block Reference Table.
+ */
+#define	BRT_OBJECT_VDEV_PREFIX	"com.fudosecurity:brt:vdev:"
+
+/*
+ * We divide each VDEV into 16MB chunks. Each chunk is represented in memory
+ * by a 16bit counter, thus 1TB VDEV requires 128kB of memory: (1TB / 16MB) * 2B
+ * Each element in this array represents how many BRT entries do we have in this
+ * chunk of storage. We always load this entire array into memory and update as
+ * needed. By having it in memory we can quickly tell (during zio_free()) if
+ * there are any BRT entries that we might need to update.
+ *
+ * This value cannot be larger than 16MB, at least as long as we support
+ * 512 byte block sizes. With 512 byte block size we can have exactly
+ * 32768 blocks in 16MB. In 32MB we could have 65536 blocks, which is one too
+ * many for a 16bit counter.
+ */
+#define	BRT_RANGESIZE	(16 * 1024 * 1024)
+_Static_assert(BRT_RANGESIZE / SPA_MINBLOCKSIZE <= UINT16_MAX,
+	"BRT_RANGESIZE is too large.");
+/*
+ * We don't want to update the whole structure every time. Maintain bitmap
+ * of dirty blocks within the regions, so that a single bit represents a
+ * block size of entcounts. For example if we have a 1PB vdev then all
+ * entcounts take 128MB of memory ((64TB / 16MB) * 2B). We can divide this
+ * 128MB array of entcounts into 32kB disk blocks, as we don't want to update
+ * the whole 128MB on disk when we have updated only a single entcount.
+ * We maintain a bitmap where each 32kB disk block within 128MB entcounts array
+ * is represented by a single bit. This gives us 4096 bits. A set bit in the
+ * bitmap means that we had a change in at least one of the 16384 entcounts
+ * that reside on a 32kB disk block (32kB / sizeof (uint16_t)).
+ */
+#define	BRT_BLOCKSIZE	(32 * 1024)
+#define	BRT_RANGESIZE_TO_NBLOCKS(size)					\
+	(((size) - 1) / BRT_BLOCKSIZE / sizeof (uint16_t) + 1)
+
+#define	BRT_LITTLE_ENDIAN	0
+#define	BRT_BIG_ENDIAN		1
+#ifdef _ZFS_LITTLE_ENDIAN
+#define	BRT_NATIVE_BYTEORDER		BRT_LITTLE_ENDIAN
+#define	BRT_NON_NATIVE_BYTEORDER	BRT_BIG_ENDIAN
+#else
+#define	BRT_NATIVE_BYTEORDER		BRT_BIG_ENDIAN
+#define	BRT_NON_NATIVE_BYTEORDER	BRT_LITTLE_ENDIAN
+#endif
+
+typedef struct brt_vdev_phys {
+	uint64_t	bvp_mos_entries;
+	uint64_t	bvp_size;
+	uint64_t	bvp_byteorder;
+	uint64_t	bvp_totalcount;
+	uint64_t	bvp_rangesize;
+	uint64_t	bvp_usedspace;
+	uint64_t	bvp_savedspace;
+} brt_vdev_phys_t;
+
+typedef struct brt_vdev {
+	/*
+	 * VDEV id.
+	 */
+	uint64_t	bv_vdevid;
+	/*
+	 * Is the structure initiated?
+	 * (bv_entcount and bv_bitmap are allocated?)
+	 */
+	boolean_t	bv_initiated;
+	/*
+	 * Object number in the MOS for the entcount array and brt_vdev_phys.
+	 */
+	uint64_t	bv_mos_brtvdev;
+	/*
+	 * Object number in the MOS for the entries table.
+	 */
+	uint64_t	bv_mos_entries;
+	/*
+	 * Entries to sync.
+	 */
+	avl_tree_t	bv_tree;
+	/*
+	 * Does the bv_entcount[] array needs byte swapping?
+	 */
+	boolean_t	bv_need_byteswap;
+	/*
+	 * Number of entries in the bv_entcount[] array.
+	 */
+	uint64_t	bv_size;
+	/*
+	 * This is the array with BRT entry count per BRT_RANGESIZE.
+	 */
+	uint16_t	*bv_entcount;
+	/*
+	 * Sum of all bv_entcount[]s.
+	 */
+	uint64_t	bv_totalcount;
+	/*
+	 * Space on disk occupied by cloned blocks (without compression).
+	 */
+	uint64_t	bv_usedspace;
+	/*
+	 * How much additional space would be occupied without block cloning.
+	 */
+	uint64_t	bv_savedspace;
+	/*
+	 * brt_vdev_phys needs updating on disk.
+	 */
+	boolean_t	bv_meta_dirty;
+	/*
+	 * bv_entcount[] needs updating on disk.
+	 */
+	boolean_t	bv_entcount_dirty;
+	/*
+	 * bv_entcount[] potentially can be a bit too big to sychronize it all
+	 * when we just changed few entcounts. The fields below allow us to
+	 * track updates to bv_entcount[] array since the last sync.
+	 * A single bit in the bv_bitmap represents as many entcounts as can
+	 * fit into a single BRT_BLOCKSIZE.
+	 * For example we have 65536 entcounts in the bv_entcount array
+	 * (so the whole array is 128kB). We updated bv_entcount[2] and
+	 * bv_entcount[5]. In that case only first bit in the bv_bitmap will
+	 * be set and we will write only first BRT_BLOCKSIZE out of 128kB.
+	 */
+	ulong_t		*bv_bitmap;
+	uint64_t	bv_nblocks;
+} brt_vdev_t;
+
+/*
+ * In-core brt
+ */
+typedef struct brt {
+	krwlock_t	brt_lock;
+	spa_t		*brt_spa;
+#define	brt_mos		brt_spa->spa_meta_objset
+	uint64_t	brt_rangesize;
+	uint64_t	brt_usedspace;
+	uint64_t	brt_savedspace;
+	avl_tree_t	brt_pending_tree[TXG_SIZE];
+	kmutex_t	brt_pending_lock[TXG_SIZE];
+	/* Sum of all entries across all bv_trees. */
+	uint64_t	brt_nentries;
+	brt_vdev_t	*brt_vdevs;
+	uint64_t	brt_nvdevs;
+} brt_t;
+
+/* Size of bre_offset / sizeof (uint64_t). */
+#define	BRT_KEY_WORDS	(1)
+
+/*
+ * In-core brt entry.
+ * On-disk we use bre_offset as the key and bre_refcount as the value.
+ */
+typedef struct brt_entry {
+	uint64_t	bre_offset;
+	uint64_t	bre_refcount;
+	avl_node_t	bre_node;
+} brt_entry_t;
+
+typedef struct brt_pending_entry {
+	blkptr_t	bpe_bp;
+	int		bpe_count;
+	avl_node_t	bpe_node;
+} brt_pending_entry_t;
+
+#ifdef	__cplusplus
+}
+#endif
+
+#endif	/* _SYS_BRT_IMPL_H */