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+/*
+ * 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 (c) 2014 by Chunwei Chen. All rights reserved.
+ * Copyright (c) 2019 by Delphix. All rights reserved.
+ */
+
+/*
+ * ARC buffer data (ABD).
+ *
+ * ABDs are an abstract data structure for the ARC which can use two
+ * different ways of storing the underlying data:
+ *
+ * (a) Linear buffer. In this case, all the data in the ABD is stored in one
+ * contiguous buffer in memory (from a zio_[data_]buf_* kmem cache).
+ *
+ * +-------------------+
+ * | ABD (linear) |
+ * | abd_flags = ... |
+ * | abd_size = ... | +--------------------------------+
+ * | abd_buf ------------->| raw buffer of size abd_size |
+ * +-------------------+ +--------------------------------+
+ * no abd_chunks
+ *
+ * (b) Scattered buffer. In this case, the data in the ABD is split into
+ * equal-sized chunks (from the abd_chunk_cache kmem_cache), with pointers
+ * to the chunks recorded in an array at the end of the ABD structure.
+ *
+ * +-------------------+
+ * | ABD (scattered) |
+ * | abd_flags = ... |
+ * | abd_size = ... |
+ * | abd_offset = 0 | +-----------+
+ * | abd_chunks[0] ----------------------------->| chunk 0 |
+ * | abd_chunks[1] ---------------------+ +-----------+
+ * | ... | | +-----------+
+ * | abd_chunks[N-1] ---------+ +------->| chunk 1 |
+ * +-------------------+ | +-----------+
+ * | ...
+ * | +-----------+
+ * +----------------->| chunk N-1 |
+ * +-----------+
+ *
+ * Linear buffers act exactly like normal buffers and are always mapped into the
+ * kernel's virtual memory space, while scattered ABD data chunks are allocated
+ * as physical pages and then mapped in only while they are actually being
+ * accessed through one of the abd_* library functions. Using scattered ABDs
+ * provides several benefits:
+ *
+ * (1) They avoid use of kmem_*, preventing performance problems where running
+ * kmem_reap on very large memory systems never finishes and causes
+ * constant TLB shootdowns.
+ *
+ * (2) Fragmentation is less of an issue since when we are at the limit of
+ * allocatable space, we won't have to search around for a long free
+ * hole in the VA space for large ARC allocations. Each chunk is mapped in
+ * individually, so even if we are using HIGHMEM (see next point) we
+ * wouldn't need to worry about finding a contiguous address range.
+ *
+ * (3) If we are not using HIGHMEM, then all physical memory is always
+ * mapped into the kernel's address space, so we also avoid the map /
+ * unmap costs on each ABD access.
+ *
+ * If we are not using HIGHMEM, scattered buffers which have only one chunk
+ * can be treated as linear buffers, because they are contiguous in the
+ * kernel's virtual address space. See abd_alloc_pages() for details.
+ *
+ * It is possible to make all ABDs linear by setting zfs_abd_scatter_enabled to
+ * B_FALSE.
+ *
+ * In addition to directly allocating a linear or scattered ABD, it is also
+ * possible to create an ABD by requesting the "sub-ABD" starting at an offset
+ * within an existing ABD. In linear buffers this is simple (set abd_buf of
+ * the new ABD to the starting point within the original raw buffer), but
+ * scattered ABDs are a little more complex. The new ABD makes a copy of the
+ * relevant abd_chunks pointers (but not the underlying data). However, to
+ * provide arbitrary rather than only chunk-aligned starting offsets, it also
+ * tracks an abd_offset field which represents the starting point of the data
+ * within the first chunk in abd_chunks. For both linear and scattered ABDs,
+ * creating an offset ABD marks the original ABD as the offset's parent, and the
+ * original ABD's abd_children refcount is incremented. This data allows us to
+ * ensure the root ABD isn't deleted before its children.
+ *
+ * Most consumers should never need to know what type of ABD they're using --
+ * the ABD public API ensures that it's possible to transparently switch from
+ * using a linear ABD to a scattered one when doing so would be beneficial.
+ *
+ * If you need to use the data within an ABD directly, if you know it's linear
+ * (because you allocated it) you can use abd_to_buf() to access the underlying
+ * raw buffer. Otherwise, you should use one of the abd_borrow_buf* functions
+ * which will allocate a raw buffer if necessary. Use the abd_return_buf*
+ * functions to return any raw buffers that are no longer necessary when you're
+ * done using them.
+ *
+ * There are a variety of ABD APIs that implement basic buffer operations:
+ * compare, copy, read, write, and fill with zeroes. If you need a custom
+ * function which progressively accesses the whole ABD, use the abd_iterate_*
+ * functions.
+ */
+
+#include <sys/abd.h>
+#include <sys/param.h>
+#include <sys/zio.h>
+#include <sys/zfs_context.h>
+#include <sys/zfs_znode.h>
+#ifdef _KERNEL
+#include <linux/scatterlist.h>
+#include <linux/kmap_compat.h>
+#else
+#define MAX_ORDER 1
+#endif
+
+typedef struct abd_stats {
+ kstat_named_t abdstat_struct_size;
+ kstat_named_t abdstat_linear_cnt;
+ kstat_named_t abdstat_linear_data_size;
+ kstat_named_t abdstat_scatter_cnt;
+ kstat_named_t abdstat_scatter_data_size;
+ kstat_named_t abdstat_scatter_chunk_waste;
+ kstat_named_t abdstat_scatter_orders[MAX_ORDER];
+ kstat_named_t abdstat_scatter_page_multi_chunk;
+ kstat_named_t abdstat_scatter_page_multi_zone;
+ kstat_named_t abdstat_scatter_page_alloc_retry;
+ kstat_named_t abdstat_scatter_sg_table_retry;
+} abd_stats_t;
+
+static abd_stats_t abd_stats = {
+ /* Amount of memory occupied by all of the abd_t struct allocations */
+ { "struct_size", KSTAT_DATA_UINT64 },
+ /*
+ * The number of linear ABDs which are currently allocated, excluding
+ * ABDs which don't own their data (for instance the ones which were
+ * allocated through abd_get_offset() and abd_get_from_buf()). If an
+ * ABD takes ownership of its buf then it will become tracked.
+ */
+ { "linear_cnt", KSTAT_DATA_UINT64 },
+ /* Amount of data stored in all linear ABDs tracked by linear_cnt */
+ { "linear_data_size", KSTAT_DATA_UINT64 },
+ /*
+ * The number of scatter ABDs which are currently allocated, excluding
+ * ABDs which don't own their data (for instance the ones which were
+ * allocated through abd_get_offset()).
+ */
+ { "scatter_cnt", KSTAT_DATA_UINT64 },
+ /* Amount of data stored in all scatter ABDs tracked by scatter_cnt */
+ { "scatter_data_size", KSTAT_DATA_UINT64 },
+ /*
+ * The amount of space wasted at the end of the last chunk across all
+ * scatter ABDs tracked by scatter_cnt.
+ */
+ { "scatter_chunk_waste", KSTAT_DATA_UINT64 },
+ /*
+ * The number of compound allocations of a given order. These
+ * allocations are spread over all currently allocated ABDs, and
+ * act as a measure of memory fragmentation.
+ */
+ { { "scatter_order_N", KSTAT_DATA_UINT64 } },
+ /*
+ * The number of scatter ABDs which contain multiple chunks.
+ * ABDs are preferentially allocated from the minimum number of
+ * contiguous multi-page chunks, a single chunk is optimal.
+ */
+ { "scatter_page_multi_chunk", KSTAT_DATA_UINT64 },
+ /*
+ * The number of scatter ABDs which are split across memory zones.
+ * ABDs are preferentially allocated using pages from a single zone.
+ */
+ { "scatter_page_multi_zone", KSTAT_DATA_UINT64 },
+ /*
+ * The total number of retries encountered when attempting to
+ * allocate the pages to populate the scatter ABD.
+ */
+ { "scatter_page_alloc_retry", KSTAT_DATA_UINT64 },
+ /*
+ * The total number of retries encountered when attempting to
+ * allocate the sg table for an ABD.
+ */
+ { "scatter_sg_table_retry", KSTAT_DATA_UINT64 },
+};
+
+#define ABDSTAT(stat) (abd_stats.stat.value.ui64)
+#define ABDSTAT_INCR(stat, val) \
+ atomic_add_64(&abd_stats.stat.value.ui64, (val))
+#define ABDSTAT_BUMP(stat) ABDSTAT_INCR(stat, 1)
+#define ABDSTAT_BUMPDOWN(stat) ABDSTAT_INCR(stat, -1)
+
+#define ABD_SCATTER(abd) (abd->abd_u.abd_scatter)
+#define ABD_BUF(abd) (abd->abd_u.abd_linear.abd_buf)
+#define abd_for_each_sg(abd, sg, n, i) \
+ for_each_sg(ABD_SCATTER(abd).abd_sgl, sg, n, i)
+
+/* see block comment above for description */
+int zfs_abd_scatter_enabled = B_TRUE;
+unsigned zfs_abd_scatter_max_order = MAX_ORDER - 1;
+
+/*
+ * zfs_abd_scatter_min_size is the minimum allocation size to use scatter
+ * ABD's. Smaller allocations will use linear ABD's which uses
+ * zio_[data_]buf_alloc().
+ *
+ * Scatter ABD's use at least one page each, so sub-page allocations waste
+ * some space when allocated as scatter (e.g. 2KB scatter allocation wastes
+ * half of each page). Using linear ABD's for small allocations means that
+ * they will be put on slabs which contain many allocations. This can
+ * improve memory efficiency, but it also makes it much harder for ARC
+ * evictions to actually free pages, because all the buffers on one slab need
+ * to be freed in order for the slab (and underlying pages) to be freed.
+ * Typically, 512B and 1KB kmem caches have 16 buffers per slab, so it's
+ * possible for them to actually waste more memory than scatter (one page per
+ * buf = wasting 3/4 or 7/8th; one buf per slab = wasting 15/16th).
+ *
+ * Spill blocks are typically 512B and are heavily used on systems running
+ * selinux with the default dnode size and the `xattr=sa` property set.
+ *
+ * By default we use linear allocations for 512B and 1KB, and scatter
+ * allocations for larger (1.5KB and up).
+ */
+int zfs_abd_scatter_min_size = 512 * 3;
+
+static kmem_cache_t *abd_cache = NULL;
+static kstat_t *abd_ksp;
+
+static inline size_t
+abd_chunkcnt_for_bytes(size_t size)
+{
+ return (P2ROUNDUP(size, PAGESIZE) / PAGESIZE);
+}
+
+#ifdef _KERNEL
+/*
+ * Mark zfs data pages so they can be excluded from kernel crash dumps
+ */
+#ifdef _LP64
+#define ABD_FILE_CACHE_PAGE 0x2F5ABDF11ECAC4E
+
+static inline void
+abd_mark_zfs_page(struct page *page)
+{
+ get_page(page);
+ SetPagePrivate(page);
+ set_page_private(page, ABD_FILE_CACHE_PAGE);
+}
+
+static inline void
+abd_unmark_zfs_page(struct page *page)
+{
+ set_page_private(page, 0UL);
+ ClearPagePrivate(page);
+ put_page(page);
+}
+#else
+#define abd_mark_zfs_page(page)
+#define abd_unmark_zfs_page(page)
+#endif /* _LP64 */
+
+#ifndef CONFIG_HIGHMEM
+
+#ifndef __GFP_RECLAIM
+#define __GFP_RECLAIM __GFP_WAIT
+#endif
+
+/*
+ * The goal is to minimize fragmentation by preferentially populating ABDs
+ * with higher order compound pages from a single zone. Allocation size is
+ * progressively decreased until it can be satisfied without performing
+ * reclaim or compaction. When necessary this function will degenerate to
+ * allocating individual pages and allowing reclaim to satisfy allocations.
+ */
+static void
+abd_alloc_pages(abd_t *abd, size_t size)
+{
+ struct list_head pages;
+ struct sg_table table;
+ struct scatterlist *sg;
+ struct page *page, *tmp_page = NULL;
+ gfp_t gfp = __GFP_NOWARN | GFP_NOIO;
+ gfp_t gfp_comp = (gfp | __GFP_NORETRY | __GFP_COMP) & ~__GFP_RECLAIM;
+ int max_order = MIN(zfs_abd_scatter_max_order, MAX_ORDER - 1);
+ int nr_pages = abd_chunkcnt_for_bytes(size);
+ int chunks = 0, zones = 0;
+ size_t remaining_size;
+ int nid = NUMA_NO_NODE;
+ int alloc_pages = 0;
+
+ INIT_LIST_HEAD(&pages);
+
+ while (alloc_pages < nr_pages) {
+ unsigned chunk_pages;
+ int order;
+
+ order = MIN(highbit64(nr_pages - alloc_pages) - 1, max_order);
+ chunk_pages = (1U << order);
+
+ page = alloc_pages_node(nid, order ? gfp_comp : gfp, order);
+ if (page == NULL) {
+ if (order == 0) {
+ ABDSTAT_BUMP(abdstat_scatter_page_alloc_retry);
+ schedule_timeout_interruptible(1);
+ } else {
+ max_order = MAX(0, order - 1);
+ }
+ continue;
+ }
+
+ list_add_tail(&page->lru, &pages);
+
+ if ((nid != NUMA_NO_NODE) && (page_to_nid(page) != nid))
+ zones++;
+
+ nid = page_to_nid(page);
+ ABDSTAT_BUMP(abdstat_scatter_orders[order]);
+ chunks++;
+ alloc_pages += chunk_pages;
+ }
+
+ ASSERT3S(alloc_pages, ==, nr_pages);
+
+ while (sg_alloc_table(&table, chunks, gfp)) {
+ ABDSTAT_BUMP(abdstat_scatter_sg_table_retry);
+ schedule_timeout_interruptible(1);
+ }
+
+ sg = table.sgl;
+ remaining_size = size;
+ list_for_each_entry_safe(page, tmp_page, &pages, lru) {
+ size_t sg_size = MIN(PAGESIZE << compound_order(page),
+ remaining_size);
+ sg_set_page(sg, page, sg_size, 0);
+ abd_mark_zfs_page(page);
+ remaining_size -= sg_size;
+
+ sg = sg_next(sg);
+ list_del(&page->lru);
+ }
+
+ /*
+ * These conditions ensure that a possible transformation to a linear
+ * ABD would be valid.
+ */
+ ASSERT(!PageHighMem(sg_page(table.sgl)));
+ ASSERT0(ABD_SCATTER(abd).abd_offset);
+
+ if (table.nents == 1) {
+ /*
+ * Since there is only one entry, this ABD can be represented
+ * as a linear buffer. All single-page (4K) ABD's can be
+ * represented this way. Some multi-page ABD's can also be
+ * represented this way, if we were able to allocate a single
+ * "chunk" (higher-order "page" which represents a power-of-2
+ * series of physically-contiguous pages). This is often the
+ * case for 2-page (8K) ABD's.
+ *
+ * Representing a single-entry scatter ABD as a linear ABD
+ * has the performance advantage of avoiding the copy (and
+ * allocation) in abd_borrow_buf_copy / abd_return_buf_copy.
+ * A performance increase of around 5% has been observed for
+ * ARC-cached reads (of small blocks which can take advantage
+ * of this).
+ *
+ * Note that this optimization is only possible because the
+ * pages are always mapped into the kernel's address space.
+ * This is not the case for highmem pages, so the
+ * optimization can not be made there.
+ */
+ abd->abd_flags |= ABD_FLAG_LINEAR;
+ abd->abd_flags |= ABD_FLAG_LINEAR_PAGE;
+ abd->abd_u.abd_linear.abd_sgl = table.sgl;
+ abd->abd_u.abd_linear.abd_buf =
+ page_address(sg_page(table.sgl));
+ } else if (table.nents > 1) {
+ ABDSTAT_BUMP(abdstat_scatter_page_multi_chunk);
+ abd->abd_flags |= ABD_FLAG_MULTI_CHUNK;
+
+ if (zones) {
+ ABDSTAT_BUMP(abdstat_scatter_page_multi_zone);
+ abd->abd_flags |= ABD_FLAG_MULTI_ZONE;
+ }
+
+ ABD_SCATTER(abd).abd_sgl = table.sgl;
+ ABD_SCATTER(abd).abd_nents = table.nents;
+ }
+}
+#else
+/*
+ * Allocate N individual pages to construct a scatter ABD. This function
+ * makes no attempt to request contiguous pages and requires the minimal
+ * number of kernel interfaces. It's designed for maximum compatibility.
+ */
+static void
+abd_alloc_pages(abd_t *abd, size_t size)
+{
+ struct scatterlist *sg = NULL;
+ struct sg_table table;
+ struct page *page;
+ gfp_t gfp = __GFP_NOWARN | GFP_NOIO;
+ int nr_pages = abd_chunkcnt_for_bytes(size);
+ int i = 0;
+
+ while (sg_alloc_table(&table, nr_pages, gfp)) {
+ ABDSTAT_BUMP(abdstat_scatter_sg_table_retry);
+ schedule_timeout_interruptible(1);
+ }
+
+ ASSERT3U(table.nents, ==, nr_pages);
+ ABD_SCATTER(abd).abd_sgl = table.sgl;
+ ABD_SCATTER(abd).abd_nents = nr_pages;
+
+ abd_for_each_sg(abd, sg, nr_pages, i) {
+ while ((page = __page_cache_alloc(gfp)) == NULL) {
+ ABDSTAT_BUMP(abdstat_scatter_page_alloc_retry);
+ schedule_timeout_interruptible(1);
+ }
+
+ ABDSTAT_BUMP(abdstat_scatter_orders[0]);
+ sg_set_page(sg, page, PAGESIZE, 0);
+ abd_mark_zfs_page(page);
+ }
+
+ if (nr_pages > 1) {
+ ABDSTAT_BUMP(abdstat_scatter_page_multi_chunk);
+ abd->abd_flags |= ABD_FLAG_MULTI_CHUNK;
+ }
+}
+#endif /* !CONFIG_HIGHMEM */
+
+static void
+abd_free_pages(abd_t *abd)
+{
+ struct scatterlist *sg = NULL;
+ struct sg_table table;
+ struct page *page;
+ int nr_pages = ABD_SCATTER(abd).abd_nents;
+ int order, i = 0;
+
+ if (abd->abd_flags & ABD_FLAG_MULTI_ZONE)
+ ABDSTAT_BUMPDOWN(abdstat_scatter_page_multi_zone);
+
+ if (abd->abd_flags & ABD_FLAG_MULTI_CHUNK)
+ ABDSTAT_BUMPDOWN(abdstat_scatter_page_multi_chunk);
+
+ abd_for_each_sg(abd, sg, nr_pages, i) {
+ page = sg_page(sg);
+ abd_unmark_zfs_page(page);
+ order = compound_order(page);
+ __free_pages(page, order);
+ ASSERT3U(sg->length, <=, PAGE_SIZE << order);
+ ABDSTAT_BUMPDOWN(abdstat_scatter_orders[order]);
+ }
+
+ table.sgl = ABD_SCATTER(abd).abd_sgl;
+ table.nents = table.orig_nents = nr_pages;
+ sg_free_table(&table);
+}
+
+#else /* _KERNEL */
+
+#ifndef PAGE_SHIFT
+#define PAGE_SHIFT (highbit64(PAGESIZE)-1)
+#endif
+
+struct page;
+
+#define zfs_kmap_atomic(chunk, km) ((void *)chunk)
+#define zfs_kunmap_atomic(addr, km) do { (void)(addr); } while (0)
+#define local_irq_save(flags) do { (void)(flags); } while (0)
+#define local_irq_restore(flags) do { (void)(flags); } while (0)
+#define nth_page(pg, i) \
+ ((struct page *)((void *)(pg) + (i) * PAGESIZE))
+
+struct scatterlist {
+ struct page *page;
+ int length;
+ int end;
+};
+
+static void
+sg_init_table(struct scatterlist *sg, int nr)
+{
+ memset(sg, 0, nr * sizeof (struct scatterlist));
+ sg[nr - 1].end = 1;
+}
+
+#define for_each_sg(sgl, sg, nr, i) \
+ for ((i) = 0, (sg) = (sgl); (i) < (nr); (i)++, (sg) = sg_next(sg))
+
+static inline void
+sg_set_page(struct scatterlist *sg, struct page *page, unsigned int len,
+ unsigned int offset)
+{
+ /* currently we don't use offset */
+ ASSERT(offset == 0);
+ sg->page = page;
+ sg->length = len;
+}
+
+static inline struct page *
+sg_page(struct scatterlist *sg)
+{
+ return (sg->page);
+}
+
+static inline struct scatterlist *
+sg_next(struct scatterlist *sg)
+{
+ if (sg->end)
+ return (NULL);
+
+ return (sg + 1);
+}
+
+static void
+abd_alloc_pages(abd_t *abd, size_t size)
+{
+ unsigned nr_pages = abd_chunkcnt_for_bytes(size);
+ struct scatterlist *sg;
+ int i;
+
+ ABD_SCATTER(abd).abd_sgl = vmem_alloc(nr_pages *
+ sizeof (struct scatterlist), KM_SLEEP);
+ sg_init_table(ABD_SCATTER(abd).abd_sgl, nr_pages);
+
+ abd_for_each_sg(abd, sg, nr_pages, i) {
+ struct page *p = umem_alloc_aligned(PAGESIZE, 64, KM_SLEEP);
+ sg_set_page(sg, p, PAGESIZE, 0);
+ }
+ ABD_SCATTER(abd).abd_nents = nr_pages;
+}
+
+static void
+abd_free_pages(abd_t *abd)
+{
+ int i, n = ABD_SCATTER(abd).abd_nents;
+ struct scatterlist *sg;
+
+ abd_for_each_sg(abd, sg, n, i) {
+ for (int j = 0; j < sg->length; j += PAGESIZE) {
+ struct page *p = nth_page(sg_page(sg), j >> PAGE_SHIFT);
+ umem_free(p, PAGESIZE);
+ }
+ }
+
+ vmem_free(ABD_SCATTER(abd).abd_sgl, n * sizeof (struct scatterlist));
+}
+
+#endif /* _KERNEL */
+
+void
+abd_init(void)
+{
+ int i;
+
+ abd_cache = kmem_cache_create("abd_t", sizeof (abd_t),
+ 0, NULL, NULL, NULL, NULL, NULL, 0);
+
+ abd_ksp = kstat_create("zfs", 0, "abdstats", "misc", KSTAT_TYPE_NAMED,
+ sizeof (abd_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL);
+ if (abd_ksp != NULL) {
+ abd_ksp->ks_data = &abd_stats;
+ kstat_install(abd_ksp);
+
+ for (i = 0; i < MAX_ORDER; i++) {
+ snprintf(abd_stats.abdstat_scatter_orders[i].name,
+ KSTAT_STRLEN, "scatter_order_%d", i);
+ abd_stats.abdstat_scatter_orders[i].data_type =
+ KSTAT_DATA_UINT64;
+ }
+ }
+}
+
+void
+abd_fini(void)
+{
+ if (abd_ksp != NULL) {
+ kstat_delete(abd_ksp);
+ abd_ksp = NULL;
+ }
+
+ if (abd_cache) {
+ kmem_cache_destroy(abd_cache);
+ abd_cache = NULL;
+ }
+}
+
+static inline void
+abd_verify(abd_t *abd)
+{
+ ASSERT3U(abd->abd_size, >, 0);
+ ASSERT3U(abd->abd_size, <=, SPA_MAXBLOCKSIZE);
+ ASSERT3U(abd->abd_flags, ==, abd->abd_flags & (ABD_FLAG_LINEAR |
+ ABD_FLAG_OWNER | ABD_FLAG_META | ABD_FLAG_MULTI_ZONE |
+ ABD_FLAG_MULTI_CHUNK | ABD_FLAG_LINEAR_PAGE));
+ IMPLY(abd->abd_parent != NULL, !(abd->abd_flags & ABD_FLAG_OWNER));
+ IMPLY(abd->abd_flags & ABD_FLAG_META, abd->abd_flags & ABD_FLAG_OWNER);
+ if (abd_is_linear(abd)) {
+ ASSERT3P(abd->abd_u.abd_linear.abd_buf, !=, NULL);
+ } else {
+ size_t n;
+ int i = 0;
+ struct scatterlist *sg = NULL;
+
+ ASSERT3U(ABD_SCATTER(abd).abd_nents, >, 0);
+ ASSERT3U(ABD_SCATTER(abd).abd_offset, <,
+ ABD_SCATTER(abd).abd_sgl->length);
+ n = ABD_SCATTER(abd).abd_nents;
+ abd_for_each_sg(abd, sg, n, i) {
+ ASSERT3P(sg_page(sg), !=, NULL);
+ }
+ }
+}
+
+static inline abd_t *
+abd_alloc_struct(void)
+{
+ abd_t *abd = kmem_cache_alloc(abd_cache, KM_PUSHPAGE);
+
+ ASSERT3P(abd, !=, NULL);
+ ABDSTAT_INCR(abdstat_struct_size, sizeof (abd_t));
+
+ return (abd);
+}
+
+static inline void
+abd_free_struct(abd_t *abd)
+{
+ kmem_cache_free(abd_cache, abd);
+ ABDSTAT_INCR(abdstat_struct_size, -(int)sizeof (abd_t));
+}
+
+/*
+ * Allocate an ABD, along with its own underlying data buffers. Use this if you
+ * don't care whether the ABD is linear or not.
+ */
+abd_t *
+abd_alloc(size_t size, boolean_t is_metadata)
+{
+ /* see the comment above zfs_abd_scatter_min_size */
+ if (!zfs_abd_scatter_enabled || size < zfs_abd_scatter_min_size)
+ return (abd_alloc_linear(size, is_metadata));
+
+ VERIFY3U(size, <=, SPA_MAXBLOCKSIZE);
+
+ abd_t *abd = abd_alloc_struct();
+ abd->abd_flags = ABD_FLAG_OWNER;
+ abd->abd_u.abd_scatter.abd_offset = 0;
+ abd_alloc_pages(abd, size);
+
+ if (is_metadata) {
+ abd->abd_flags |= ABD_FLAG_META;
+ }
+ abd->abd_size = size;
+ abd->abd_parent = NULL;
+ zfs_refcount_create(&abd->abd_children);
+
+ ABDSTAT_BUMP(abdstat_scatter_cnt);
+ ABDSTAT_INCR(abdstat_scatter_data_size, size);
+ ABDSTAT_INCR(abdstat_scatter_chunk_waste,
+ P2ROUNDUP(size, PAGESIZE) - size);
+
+ return (abd);
+}
+
+static void
+abd_free_scatter(abd_t *abd)
+{
+ abd_free_pages(abd);
+
+ zfs_refcount_destroy(&abd->abd_children);
+ ABDSTAT_BUMPDOWN(abdstat_scatter_cnt);
+ ABDSTAT_INCR(abdstat_scatter_data_size, -(int)abd->abd_size);
+ ABDSTAT_INCR(abdstat_scatter_chunk_waste,
+ (int)abd->abd_size - (int)P2ROUNDUP(abd->abd_size, PAGESIZE));
+
+ abd_free_struct(abd);
+}
+
+/*
+ * Allocate an ABD that must be linear, along with its own underlying data
+ * buffer. Only use this when it would be very annoying to write your ABD
+ * consumer with a scattered ABD.
+ */
+abd_t *
+abd_alloc_linear(size_t size, boolean_t is_metadata)
+{
+ abd_t *abd = abd_alloc_struct();
+
+ VERIFY3U(size, <=, SPA_MAXBLOCKSIZE);
+
+ abd->abd_flags = ABD_FLAG_LINEAR | ABD_FLAG_OWNER;
+ if (is_metadata) {
+ abd->abd_flags |= ABD_FLAG_META;
+ }
+ abd->abd_size = size;
+ abd->abd_parent = NULL;
+ zfs_refcount_create(&abd->abd_children);
+
+ if (is_metadata) {
+ abd->abd_u.abd_linear.abd_buf = zio_buf_alloc(size);
+ } else {
+ abd->abd_u.abd_linear.abd_buf = zio_data_buf_alloc(size);
+ }
+
+ ABDSTAT_BUMP(abdstat_linear_cnt);
+ ABDSTAT_INCR(abdstat_linear_data_size, size);
+
+ return (abd);
+}
+
+static void
+abd_free_linear(abd_t *abd)
+{
+ if (abd_is_linear_page(abd)) {
+ /* Transform it back into a scatter ABD for freeing */
+ struct scatterlist *sg = abd->abd_u.abd_linear.abd_sgl;
+ abd->abd_flags &= ~ABD_FLAG_LINEAR;
+ abd->abd_flags &= ~ABD_FLAG_LINEAR_PAGE;
+ ABD_SCATTER(abd).abd_nents = 1;
+ ABD_SCATTER(abd).abd_offset = 0;
+ ABD_SCATTER(abd).abd_sgl = sg;
+ abd_free_scatter(abd);
+ return;
+ }
+ if (abd->abd_flags & ABD_FLAG_META) {
+ zio_buf_free(abd->abd_u.abd_linear.abd_buf, abd->abd_size);
+ } else {
+ zio_data_buf_free(abd->abd_u.abd_linear.abd_buf, abd->abd_size);
+ }
+
+ zfs_refcount_destroy(&abd->abd_children);
+ ABDSTAT_BUMPDOWN(abdstat_linear_cnt);
+ ABDSTAT_INCR(abdstat_linear_data_size, -(int)abd->abd_size);
+
+ abd_free_struct(abd);
+}
+
+/*
+ * Free an ABD. Only use this on ABDs allocated with abd_alloc() or
+ * abd_alloc_linear().
+ */
+void
+abd_free(abd_t *abd)
+{
+ abd_verify(abd);
+ ASSERT3P(abd->abd_parent, ==, NULL);
+ ASSERT(abd->abd_flags & ABD_FLAG_OWNER);
+ if (abd_is_linear(abd))
+ abd_free_linear(abd);
+ else
+ abd_free_scatter(abd);
+}
+
+/*
+ * Allocate an ABD of the same format (same metadata flag, same scatterize
+ * setting) as another ABD.
+ */
+abd_t *
+abd_alloc_sametype(abd_t *sabd, size_t size)
+{
+ boolean_t is_metadata = (sabd->abd_flags & ABD_FLAG_META) != 0;
+ if (abd_is_linear(sabd) &&
+ !abd_is_linear_page(sabd)) {
+ return (abd_alloc_linear(size, is_metadata));
+ } else {
+ return (abd_alloc(size, is_metadata));
+ }
+}
+
+/*
+ * If we're going to use this ABD for doing I/O using the block layer, the
+ * consumer of the ABD data doesn't care if it's scattered or not, and we don't
+ * plan to store this ABD in memory for a long period of time, we should
+ * allocate the ABD type that requires the least data copying to do the I/O.
+ *
+ * On Illumos this is linear ABDs, however if ldi_strategy() can ever issue I/Os
+ * using a scatter/gather list we should switch to that and replace this call
+ * with vanilla abd_alloc().
+ *
+ * On Linux the optimal thing to do would be to use abd_get_offset() and
+ * construct a new ABD which shares the original pages thereby eliminating
+ * the copy. But for the moment a new linear ABD is allocated until this
+ * performance optimization can be implemented.
+ */
+abd_t *
+abd_alloc_for_io(size_t size, boolean_t is_metadata)
+{
+ return (abd_alloc(size, is_metadata));
+}
+
+/*
+ * Allocate a new ABD to point to offset off of sabd. It shares the underlying
+ * buffer data with sabd. Use abd_put() to free. sabd must not be freed while
+ * any derived ABDs exist.
+ */
+static inline abd_t *
+abd_get_offset_impl(abd_t *sabd, size_t off, size_t size)
+{
+ abd_t *abd;
+
+ abd_verify(sabd);
+ ASSERT3U(off, <=, sabd->abd_size);
+
+ if (abd_is_linear(sabd)) {
+ abd = abd_alloc_struct();
+
+ /*
+ * Even if this buf is filesystem metadata, we only track that
+ * if we own the underlying data buffer, which is not true in
+ * this case. Therefore, we don't ever use ABD_FLAG_META here.
+ */
+ abd->abd_flags = ABD_FLAG_LINEAR;
+
+ abd->abd_u.abd_linear.abd_buf =
+ (char *)sabd->abd_u.abd_linear.abd_buf + off;
+ } else {
+ int i = 0;
+ struct scatterlist *sg = NULL;
+ size_t new_offset = sabd->abd_u.abd_scatter.abd_offset + off;
+
+ abd = abd_alloc_struct();
+
+ /*
+ * Even if this buf is filesystem metadata, we only track that
+ * if we own the underlying data buffer, which is not true in
+ * this case. Therefore, we don't ever use ABD_FLAG_META here.
+ */
+ abd->abd_flags = 0;
+
+ abd_for_each_sg(sabd, sg, ABD_SCATTER(sabd).abd_nents, i) {
+ if (new_offset < sg->length)
+ break;
+ new_offset -= sg->length;
+ }
+
+ ABD_SCATTER(abd).abd_sgl = sg;
+ ABD_SCATTER(abd).abd_offset = new_offset;
+ ABD_SCATTER(abd).abd_nents = ABD_SCATTER(sabd).abd_nents - i;
+ }
+
+ abd->abd_size = size;
+ abd->abd_parent = sabd;
+ zfs_refcount_create(&abd->abd_children);
+ (void) zfs_refcount_add_many(&sabd->abd_children, abd->abd_size, abd);
+
+ return (abd);
+}
+
+abd_t *
+abd_get_offset(abd_t *sabd, size_t off)
+{
+ size_t size = sabd->abd_size > off ? sabd->abd_size - off : 0;
+
+ VERIFY3U(size, >, 0);
+
+ return (abd_get_offset_impl(sabd, off, size));
+}
+
+abd_t *
+abd_get_offset_size(abd_t *sabd, size_t off, size_t size)
+{
+ ASSERT3U(off + size, <=, sabd->abd_size);
+
+ return (abd_get_offset_impl(sabd, off, size));
+}
+
+/*
+ * Allocate a linear ABD structure for buf. You must free this with abd_put()
+ * since the resulting ABD doesn't own its own buffer.
+ */
+abd_t *
+abd_get_from_buf(void *buf, size_t size)
+{
+ abd_t *abd = abd_alloc_struct();
+
+ VERIFY3U(size, <=, SPA_MAXBLOCKSIZE);
+
+ /*
+ * Even if this buf is filesystem metadata, we only track that if we
+ * own the underlying data buffer, which is not true in this case.
+ * Therefore, we don't ever use ABD_FLAG_META here.
+ */
+ abd->abd_flags = ABD_FLAG_LINEAR;
+ abd->abd_size = size;
+ abd->abd_parent = NULL;
+ zfs_refcount_create(&abd->abd_children);
+
+ abd->abd_u.abd_linear.abd_buf = buf;
+
+ return (abd);
+}
+
+/*
+ * Free an ABD allocated from abd_get_offset() or abd_get_from_buf(). Will not
+ * free the underlying scatterlist or buffer.
+ */
+void
+abd_put(abd_t *abd)
+{
+ abd_verify(abd);
+ ASSERT(!(abd->abd_flags & ABD_FLAG_OWNER));
+
+ if (abd->abd_parent != NULL) {
+ (void) zfs_refcount_remove_many(&abd->abd_parent->abd_children,
+ abd->abd_size, abd);
+ }
+
+ zfs_refcount_destroy(&abd->abd_children);
+ abd_free_struct(abd);
+}
+
+/*
+ * Get the raw buffer associated with a linear ABD.
+ */
+void *
+abd_to_buf(abd_t *abd)
+{
+ ASSERT(abd_is_linear(abd));
+ abd_verify(abd);
+ return (abd->abd_u.abd_linear.abd_buf);
+}
+
+/*
+ * Borrow a raw buffer from an ABD without copying the contents of the ABD
+ * into the buffer. If the ABD is scattered, this will allocate a raw buffer
+ * whose contents are undefined. To copy over the existing data in the ABD, use
+ * abd_borrow_buf_copy() instead.
+ */
+void *
+abd_borrow_buf(abd_t *abd, size_t n)
+{
+ void *buf;
+ abd_verify(abd);
+ ASSERT3U(abd->abd_size, >=, n);
+ if (abd_is_linear(abd)) {
+ buf = abd_to_buf(abd);
+ } else {
+ buf = zio_buf_alloc(n);
+ }
+ (void) zfs_refcount_add_many(&abd->abd_children, n, buf);
+
+ return (buf);
+}
+
+void *
+abd_borrow_buf_copy(abd_t *abd, size_t n)
+{
+ void *buf = abd_borrow_buf(abd, n);
+ if (!abd_is_linear(abd)) {
+ abd_copy_to_buf(buf, abd, n);
+ }
+ return (buf);
+}
+
+/*
+ * Return a borrowed raw buffer to an ABD. If the ABD is scattered, this will
+ * not change the contents of the ABD and will ASSERT that you didn't modify
+ * the buffer since it was borrowed. If you want any changes you made to buf to
+ * be copied back to abd, use abd_return_buf_copy() instead.
+ */
+void
+abd_return_buf(abd_t *abd, void *buf, size_t n)
+{
+ abd_verify(abd);
+ ASSERT3U(abd->abd_size, >=, n);
+ if (abd_is_linear(abd)) {
+ ASSERT3P(buf, ==, abd_to_buf(abd));
+ } else {
+ ASSERT0(abd_cmp_buf(abd, buf, n));
+ zio_buf_free(buf, n);
+ }
+ (void) zfs_refcount_remove_many(&abd->abd_children, n, buf);
+}
+
+void
+abd_return_buf_copy(abd_t *abd, void *buf, size_t n)
+{
+ if (!abd_is_linear(abd)) {
+ abd_copy_from_buf(abd, buf, n);
+ }
+ abd_return_buf(abd, buf, n);
+}
+
+/*
+ * Give this ABD ownership of the buffer that it's storing. Can only be used on
+ * linear ABDs which were allocated via abd_get_from_buf(), or ones allocated
+ * with abd_alloc_linear() which subsequently released ownership of their buf
+ * with abd_release_ownership_of_buf().
+ */
+void
+abd_take_ownership_of_buf(abd_t *abd, boolean_t is_metadata)
+{
+ ASSERT(abd_is_linear(abd));
+ ASSERT(!(abd->abd_flags & ABD_FLAG_OWNER));
+ abd_verify(abd);
+
+ abd->abd_flags |= ABD_FLAG_OWNER;
+ if (is_metadata) {
+ abd->abd_flags |= ABD_FLAG_META;
+ }
+
+ ABDSTAT_BUMP(abdstat_linear_cnt);
+ ABDSTAT_INCR(abdstat_linear_data_size, abd->abd_size);
+}
+
+void
+abd_release_ownership_of_buf(abd_t *abd)
+{
+ ASSERT(abd_is_linear(abd));
+ ASSERT(abd->abd_flags & ABD_FLAG_OWNER);
+
+ /*
+ * abd_free() needs to handle LINEAR_PAGE ABD's specially.
+ * Since that flag does not survive the
+ * abd_release_ownership_of_buf() -> abd_get_from_buf() ->
+ * abd_take_ownership_of_buf() sequence, we don't allow releasing
+ * these "linear but not zio_[data_]buf_alloc()'ed" ABD's.
+ */
+ ASSERT(!abd_is_linear_page(abd));
+
+ abd_verify(abd);
+
+ abd->abd_flags &= ~ABD_FLAG_OWNER;
+ /* Disable this flag since we no longer own the data buffer */
+ abd->abd_flags &= ~ABD_FLAG_META;
+
+ ABDSTAT_BUMPDOWN(abdstat_linear_cnt);
+ ABDSTAT_INCR(abdstat_linear_data_size, -(int)abd->abd_size);
+}
+
+#ifndef HAVE_1ARG_KMAP_ATOMIC
+#define NR_KM_TYPE (6)
+#ifdef _KERNEL
+int km_table[NR_KM_TYPE] = {
+ KM_USER0,
+ KM_USER1,
+ KM_BIO_SRC_IRQ,
+ KM_BIO_DST_IRQ,
+ KM_PTE0,
+ KM_PTE1,
+};
+#endif
+#endif
+
+struct abd_iter {
+ /* public interface */
+ void *iter_mapaddr; /* addr corresponding to iter_pos */
+ size_t iter_mapsize; /* length of data valid at mapaddr */
+
+ /* private */
+ abd_t *iter_abd; /* ABD being iterated through */
+ size_t iter_pos;
+ size_t iter_offset; /* offset in current sg/abd_buf, */
+ /* abd_offset included */
+ struct scatterlist *iter_sg; /* current sg */
+#ifndef HAVE_1ARG_KMAP_ATOMIC
+ int iter_km; /* KM_* for kmap_atomic */
+#endif
+};
+
+/*
+ * Initialize the abd_iter.
+ */
+static void
+abd_iter_init(struct abd_iter *aiter, abd_t *abd, int km_type)
+{
+ abd_verify(abd);
+ aiter->iter_abd = abd;
+ aiter->iter_mapaddr = NULL;
+ aiter->iter_mapsize = 0;
+ aiter->iter_pos = 0;
+ if (abd_is_linear(abd)) {
+ aiter->iter_offset = 0;
+ aiter->iter_sg = NULL;
+ } else {
+ aiter->iter_offset = ABD_SCATTER(abd).abd_offset;
+ aiter->iter_sg = ABD_SCATTER(abd).abd_sgl;
+ }
+#ifndef HAVE_1ARG_KMAP_ATOMIC
+ ASSERT3U(km_type, <, NR_KM_TYPE);
+ aiter->iter_km = km_type;
+#endif
+}
+
+/*
+ * Advance the iterator by a certain amount. Cannot be called when a chunk is
+ * in use. This can be safely called when the aiter has already exhausted, in
+ * which case this does nothing.
+ */
+static void
+abd_iter_advance(struct abd_iter *aiter, size_t amount)
+{
+ ASSERT3P(aiter->iter_mapaddr, ==, NULL);
+ ASSERT0(aiter->iter_mapsize);
+
+ /* There's nothing left to advance to, so do nothing */
+ if (aiter->iter_pos == aiter->iter_abd->abd_size)
+ return;
+
+ aiter->iter_pos += amount;
+ aiter->iter_offset += amount;
+ if (!abd_is_linear(aiter->iter_abd)) {
+ while (aiter->iter_offset >= aiter->iter_sg->length) {
+ aiter->iter_offset -= aiter->iter_sg->length;
+ aiter->iter_sg = sg_next(aiter->iter_sg);
+ if (aiter->iter_sg == NULL) {
+ ASSERT0(aiter->iter_offset);
+ break;
+ }
+ }
+ }
+}
+
+/*
+ * Map the current chunk into aiter. This can be safely called when the aiter
+ * has already exhausted, in which case this does nothing.
+ */
+static void
+abd_iter_map(struct abd_iter *aiter)
+{
+ void *paddr;
+ size_t offset = 0;
+
+ ASSERT3P(aiter->iter_mapaddr, ==, NULL);
+ ASSERT0(aiter->iter_mapsize);
+
+ /* There's nothing left to iterate over, so do nothing */
+ if (aiter->iter_pos == aiter->iter_abd->abd_size)
+ return;
+
+ if (abd_is_linear(aiter->iter_abd)) {
+ ASSERT3U(aiter->iter_pos, ==, aiter->iter_offset);
+ offset = aiter->iter_offset;
+ aiter->iter_mapsize = aiter->iter_abd->abd_size - offset;
+ paddr = aiter->iter_abd->abd_u.abd_linear.abd_buf;
+ } else {
+ offset = aiter->iter_offset;
+ aiter->iter_mapsize = MIN(aiter->iter_sg->length - offset,
+ aiter->iter_abd->abd_size - aiter->iter_pos);
+
+ paddr = zfs_kmap_atomic(sg_page(aiter->iter_sg),
+ km_table[aiter->iter_km]);
+ }
+
+ aiter->iter_mapaddr = (char *)paddr + offset;
+}
+
+/*
+ * Unmap the current chunk from aiter. This can be safely called when the aiter
+ * has already exhausted, in which case this does nothing.
+ */
+static void
+abd_iter_unmap(struct abd_iter *aiter)
+{
+ /* There's nothing left to unmap, so do nothing */
+ if (aiter->iter_pos == aiter->iter_abd->abd_size)
+ return;
+
+ if (!abd_is_linear(aiter->iter_abd)) {
+ /* LINTED E_FUNC_SET_NOT_USED */
+ zfs_kunmap_atomic(aiter->iter_mapaddr - aiter->iter_offset,
+ km_table[aiter->iter_km]);
+ }
+
+ ASSERT3P(aiter->iter_mapaddr, !=, NULL);
+ ASSERT3U(aiter->iter_mapsize, >, 0);
+
+ aiter->iter_mapaddr = NULL;
+ aiter->iter_mapsize = 0;
+}
+
+int
+abd_iterate_func(abd_t *abd, size_t off, size_t size,
+ abd_iter_func_t *func, void *private)
+{
+ int ret = 0;
+ struct abd_iter aiter;
+
+ abd_verify(abd);
+ ASSERT3U(off + size, <=, abd->abd_size);
+
+ abd_iter_init(&aiter, abd, 0);
+ abd_iter_advance(&aiter, off);
+
+ while (size > 0) {
+ abd_iter_map(&aiter);
+
+ size_t len = MIN(aiter.iter_mapsize, size);
+ ASSERT3U(len, >, 0);
+
+ ret = func(aiter.iter_mapaddr, len, private);
+
+ abd_iter_unmap(&aiter);
+
+ if (ret != 0)
+ break;
+
+ size -= len;
+ abd_iter_advance(&aiter, len);
+ }
+
+ return (ret);
+}
+
+struct buf_arg {
+ void *arg_buf;
+};
+
+static int
+abd_copy_to_buf_off_cb(void *buf, size_t size, void *private)
+{
+ struct buf_arg *ba_ptr = private;
+
+ (void) memcpy(ba_ptr->arg_buf, buf, size);
+ ba_ptr->arg_buf = (char *)ba_ptr->arg_buf + size;
+
+ return (0);
+}
+
+/*
+ * Copy abd to buf. (off is the offset in abd.)
+ */
+void
+abd_copy_to_buf_off(void *buf, abd_t *abd, size_t off, size_t size)
+{
+ struct buf_arg ba_ptr = { buf };
+
+ (void) abd_iterate_func(abd, off, size, abd_copy_to_buf_off_cb,
+ &ba_ptr);
+}
+
+static int
+abd_cmp_buf_off_cb(void *buf, size_t size, void *private)
+{
+ int ret;
+ struct buf_arg *ba_ptr = private;
+
+ ret = memcmp(buf, ba_ptr->arg_buf, size);
+ ba_ptr->arg_buf = (char *)ba_ptr->arg_buf + size;
+
+ return (ret);
+}
+
+/*
+ * Compare the contents of abd to buf. (off is the offset in abd.)
+ */
+int
+abd_cmp_buf_off(abd_t *abd, const void *buf, size_t off, size_t size)
+{
+ struct buf_arg ba_ptr = { (void *) buf };
+
+ return (abd_iterate_func(abd, off, size, abd_cmp_buf_off_cb, &ba_ptr));
+}
+
+static int
+abd_copy_from_buf_off_cb(void *buf, size_t size, void *private)
+{
+ struct buf_arg *ba_ptr = private;
+
+ (void) memcpy(buf, ba_ptr->arg_buf, size);
+ ba_ptr->arg_buf = (char *)ba_ptr->arg_buf + size;
+
+ return (0);
+}
+
+/*
+ * Copy from buf to abd. (off is the offset in abd.)
+ */
+void
+abd_copy_from_buf_off(abd_t *abd, const void *buf, size_t off, size_t size)
+{
+ struct buf_arg ba_ptr = { (void *) buf };
+
+ (void) abd_iterate_func(abd, off, size, abd_copy_from_buf_off_cb,
+ &ba_ptr);
+}
+
+/*ARGSUSED*/
+static int
+abd_zero_off_cb(void *buf, size_t size, void *private)
+{
+ (void) memset(buf, 0, size);
+ return (0);
+}
+
+/*
+ * Zero out the abd from a particular offset to the end.
+ */
+void
+abd_zero_off(abd_t *abd, size_t off, size_t size)
+{
+ (void) abd_iterate_func(abd, off, size, abd_zero_off_cb, NULL);
+}
+
+/*
+ * Iterate over two ABDs and call func incrementally on the two ABDs' data in
+ * equal-sized chunks (passed to func as raw buffers). func could be called many
+ * times during this iteration.
+ */
+int
+abd_iterate_func2(abd_t *dabd, abd_t *sabd, size_t doff, size_t soff,
+ size_t size, abd_iter_func2_t *func, void *private)
+{
+ int ret = 0;
+ struct abd_iter daiter, saiter;
+
+ abd_verify(dabd);
+ abd_verify(sabd);
+
+ ASSERT3U(doff + size, <=, dabd->abd_size);
+ ASSERT3U(soff + size, <=, sabd->abd_size);
+
+ abd_iter_init(&daiter, dabd, 0);
+ abd_iter_init(&saiter, sabd, 1);
+ abd_iter_advance(&daiter, doff);
+ abd_iter_advance(&saiter, soff);
+
+ while (size > 0) {
+ abd_iter_map(&daiter);
+ abd_iter_map(&saiter);
+
+ size_t dlen = MIN(daiter.iter_mapsize, size);
+ size_t slen = MIN(saiter.iter_mapsize, size);
+ size_t len = MIN(dlen, slen);
+ ASSERT(dlen > 0 || slen > 0);
+
+ ret = func(daiter.iter_mapaddr, saiter.iter_mapaddr, len,
+ private);
+
+ abd_iter_unmap(&saiter);
+ abd_iter_unmap(&daiter);
+
+ if (ret != 0)
+ break;
+
+ size -= len;
+ abd_iter_advance(&daiter, len);
+ abd_iter_advance(&saiter, len);
+ }
+
+ return (ret);
+}
+
+/*ARGSUSED*/
+static int
+abd_copy_off_cb(void *dbuf, void *sbuf, size_t size, void *private)
+{
+ (void) memcpy(dbuf, sbuf, size);
+ return (0);
+}
+
+/*
+ * Copy from sabd to dabd starting from soff and doff.
+ */
+void
+abd_copy_off(abd_t *dabd, abd_t *sabd, size_t doff, size_t soff, size_t size)
+{
+ (void) abd_iterate_func2(dabd, sabd, doff, soff, size,
+ abd_copy_off_cb, NULL);
+}
+
+/*ARGSUSED*/
+static int
+abd_cmp_cb(void *bufa, void *bufb, size_t size, void *private)
+{
+ return (memcmp(bufa, bufb, size));
+}
+
+/*
+ * Compares the contents of two ABDs.
+ */
+int
+abd_cmp(abd_t *dabd, abd_t *sabd)
+{
+ ASSERT3U(dabd->abd_size, ==, sabd->abd_size);
+ return (abd_iterate_func2(dabd, sabd, 0, 0, dabd->abd_size,
+ abd_cmp_cb, NULL));
+}
+
+/*
+ * Iterate over code ABDs and a data ABD and call @func_raidz_gen.
+ *
+ * @cabds parity ABDs, must have equal size
+ * @dabd data ABD. Can be NULL (in this case @dsize = 0)
+ * @func_raidz_gen should be implemented so that its behaviour
+ * is the same when taking linear and when taking scatter
+ */
+void
+abd_raidz_gen_iterate(abd_t **cabds, abd_t *dabd,
+ ssize_t csize, ssize_t dsize, const unsigned parity,
+ void (*func_raidz_gen)(void **, const void *, size_t, size_t))
+{
+ int i;
+ ssize_t len, dlen;
+ struct abd_iter caiters[3];
+ struct abd_iter daiter = {0};
+ void *caddrs[3];
+ unsigned long flags;
+
+ ASSERT3U(parity, <=, 3);
+
+ for (i = 0; i < parity; i++)
+ abd_iter_init(&caiters[i], cabds[i], i);
+
+ if (dabd)
+ abd_iter_init(&daiter, dabd, i);
+
+ ASSERT3S(dsize, >=, 0);
+
+ local_irq_save(flags);
+ while (csize > 0) {
+ len = csize;
+
+ if (dabd && dsize > 0)
+ abd_iter_map(&daiter);
+
+ for (i = 0; i < parity; i++) {
+ abd_iter_map(&caiters[i]);
+ caddrs[i] = caiters[i].iter_mapaddr;
+ }
+
+ switch (parity) {
+ case 3:
+ len = MIN(caiters[2].iter_mapsize, len);
+ /* falls through */
+ case 2:
+ len = MIN(caiters[1].iter_mapsize, len);
+ /* falls through */
+ case 1:
+ len = MIN(caiters[0].iter_mapsize, len);
+ }
+
+ /* must be progressive */
+ ASSERT3S(len, >, 0);
+
+ if (dabd && dsize > 0) {
+ /* this needs precise iter.length */
+ len = MIN(daiter.iter_mapsize, len);
+ dlen = len;
+ } else
+ dlen = 0;
+
+ /* must be progressive */
+ ASSERT3S(len, >, 0);
+ /*
+ * The iterated function likely will not do well if each
+ * segment except the last one is not multiple of 512 (raidz).
+ */
+ ASSERT3U(((uint64_t)len & 511ULL), ==, 0);
+
+ func_raidz_gen(caddrs, daiter.iter_mapaddr, len, dlen);
+
+ for (i = parity-1; i >= 0; i--) {
+ abd_iter_unmap(&caiters[i]);
+ abd_iter_advance(&caiters[i], len);
+ }
+
+ if (dabd && dsize > 0) {
+ abd_iter_unmap(&daiter);
+ abd_iter_advance(&daiter, dlen);
+ dsize -= dlen;
+ }
+
+ csize -= len;
+
+ ASSERT3S(dsize, >=, 0);
+ ASSERT3S(csize, >=, 0);
+ }
+ local_irq_restore(flags);
+}
+
+/*
+ * Iterate over code ABDs and data reconstruction target ABDs and call
+ * @func_raidz_rec. Function maps at most 6 pages atomically.
+ *
+ * @cabds parity ABDs, must have equal size
+ * @tabds rec target ABDs, at most 3
+ * @tsize size of data target columns
+ * @func_raidz_rec expects syndrome data in target columns. Function
+ * reconstructs data and overwrites target columns.
+ */
+void
+abd_raidz_rec_iterate(abd_t **cabds, abd_t **tabds,
+ ssize_t tsize, const unsigned parity,
+ void (*func_raidz_rec)(void **t, const size_t tsize, void **c,
+ const unsigned *mul),
+ const unsigned *mul)
+{
+ int i;
+ ssize_t len;
+ struct abd_iter citers[3];
+ struct abd_iter xiters[3];
+ void *caddrs[3], *xaddrs[3];
+ unsigned long flags;
+
+ ASSERT3U(parity, <=, 3);
+
+ for (i = 0; i < parity; i++) {
+ abd_iter_init(&citers[i], cabds[i], 2*i);
+ abd_iter_init(&xiters[i], tabds[i], 2*i+1);
+ }
+
+ local_irq_save(flags);
+ while (tsize > 0) {
+
+ for (i = 0; i < parity; i++) {
+ abd_iter_map(&citers[i]);
+ abd_iter_map(&xiters[i]);
+ caddrs[i] = citers[i].iter_mapaddr;
+ xaddrs[i] = xiters[i].iter_mapaddr;
+ }
+
+ len = tsize;
+ switch (parity) {
+ case 3:
+ len = MIN(xiters[2].iter_mapsize, len);
+ len = MIN(citers[2].iter_mapsize, len);
+ /* falls through */
+ case 2:
+ len = MIN(xiters[1].iter_mapsize, len);
+ len = MIN(citers[1].iter_mapsize, len);
+ /* falls through */
+ case 1:
+ len = MIN(xiters[0].iter_mapsize, len);
+ len = MIN(citers[0].iter_mapsize, len);
+ }
+ /* must be progressive */
+ ASSERT3S(len, >, 0);
+ /*
+ * The iterated function likely will not do well if each
+ * segment except the last one is not multiple of 512 (raidz).
+ */
+ ASSERT3U(((uint64_t)len & 511ULL), ==, 0);
+
+ func_raidz_rec(xaddrs, len, caddrs, mul);
+
+ for (i = parity-1; i >= 0; i--) {
+ abd_iter_unmap(&xiters[i]);
+ abd_iter_unmap(&citers[i]);
+ abd_iter_advance(&xiters[i], len);
+ abd_iter_advance(&citers[i], len);
+ }
+
+ tsize -= len;
+ ASSERT3S(tsize, >=, 0);
+ }
+ local_irq_restore(flags);
+}
+
+#if defined(_KERNEL)
+/*
+ * bio_nr_pages for ABD.
+ * @off is the offset in @abd
+ */
+unsigned long
+abd_nr_pages_off(abd_t *abd, unsigned int size, size_t off)
+{
+ unsigned long pos;
+
+ if (abd_is_linear(abd))
+ pos = (unsigned long)abd_to_buf(abd) + off;
+ else
+ pos = abd->abd_u.abd_scatter.abd_offset + off;
+
+ return ((pos + size + PAGESIZE - 1) >> PAGE_SHIFT) -
+ (pos >> PAGE_SHIFT);
+}
+
+/*
+ * bio_map for scatter ABD.
+ * @off is the offset in @abd
+ * Remaining IO size is returned
+ */
+unsigned int
+abd_scatter_bio_map_off(struct bio *bio, abd_t *abd,
+ unsigned int io_size, size_t off)
+{
+ int i;
+ struct abd_iter aiter;
+
+ ASSERT(!abd_is_linear(abd));
+ ASSERT3U(io_size, <=, abd->abd_size - off);
+
+ abd_iter_init(&aiter, abd, 0);
+ abd_iter_advance(&aiter, off);
+
+ for (i = 0; i < bio->bi_max_vecs; i++) {
+ struct page *pg;
+ size_t len, sgoff, pgoff;
+ struct scatterlist *sg;
+
+ if (io_size <= 0)
+ break;
+
+ sg = aiter.iter_sg;
+ sgoff = aiter.iter_offset;
+ pgoff = sgoff & (PAGESIZE - 1);
+ len = MIN(io_size, PAGESIZE - pgoff);
+ ASSERT(len > 0);
+
+ pg = nth_page(sg_page(sg), sgoff >> PAGE_SHIFT);
+ if (bio_add_page(bio, pg, len, pgoff) != len)
+ break;
+
+ io_size -= len;
+ abd_iter_advance(&aiter, len);
+ }
+
+ return (io_size);
+}
+
+/* Tunable Parameters */
+module_param(zfs_abd_scatter_enabled, int, 0644);
+MODULE_PARM_DESC(zfs_abd_scatter_enabled,
+ "Toggle whether ABD allocations must be linear.");
+module_param(zfs_abd_scatter_min_size, int, 0644);
+MODULE_PARM_DESC(zfs_abd_scatter_min_size,
+ "Minimum size of scatter allocations.");
+/* CSTYLED */
+module_param(zfs_abd_scatter_max_order, uint, 0644);
+MODULE_PARM_DESC(zfs_abd_scatter_max_order,
+ "Maximum order allocation used for a scatter ABD.");
+#endif