Defer resilver only when progress is above a threshold

[zfs.git] / lib / libzpool / abd_os.c

/*
 * 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) 2014 by Chunwei Chen. All rights reserved.
 * Copyright (c) 2019 by Delphix. All rights reserved.
 * Copyright (c) 2023, 2024, Klara Inc.
 */

#include <sys/abd_impl.h>
#include <sys/param.h>
#include <sys/zio.h>
#include <sys/arc.h>
#include <sys/zfs_context.h>
#include <sys/zfs_znode.h>

/*
 * We're simulating scatter/gather with 4K allocations, since that's more like
 * what a typical kernel does.
 */
#define ABD_PAGESIZE    (4096)
#define ABD_PAGESHIFT   (12)
#define ABD_PAGEMASK    (ABD_PAGESIZE-1)

/*
 * See rationale in module/os/linux/zfs/abd_os.c, but in userspace this is
 * mostly useful to get a mix of linear and scatter ABDs for testing.
 */
#define ABD_SCATTER_MIN_SIZE    (512 * 3)

abd_t *abd_zero_scatter = NULL;

static uint_t
abd_iovcnt_for_bytes(size_t size)
{
        /*
         * Each iovec points to a 4K page. There's no real reason to do this
         * in userspace, but our whole point here is to make it feel a bit
         * more like a real paged memory model.
         */
        return (P2ROUNDUP(size, ABD_PAGESIZE) / ABD_PAGESIZE);
}

abd_t *
abd_alloc_struct_impl(size_t size)
{
        /*
         * Zero-sized means it will be used for a linear or gang abd, so just
         * allocate the abd itself and return.
         */
        if (size == 0)
                return (umem_alloc(sizeof (abd_t), UMEM_NOFAIL));

        /*
         * Allocating for a scatter abd, so compute how many ABD_PAGESIZE
         * iovecs we will need to hold this size. Append that allocation to the
         * end. Note that struct abd_scatter has includes abd_iov[1], so we
         * allocate one less iovec than we need.
         *
         * Note we're not allocating the pages proper, just the iovec pointers.
         * That's down in abd_alloc_chunks. We _could_ do it here in a single
         * allocation, but it's fiddly and harder to read for no real gain.
         */
        uint_t n = abd_iovcnt_for_bytes(size);
        abd_t *abd = umem_alloc(sizeof (abd_t) + (n-1) * sizeof (struct iovec),
            UMEM_NOFAIL);
        ABD_SCATTER(abd).abd_offset = 0;
        ABD_SCATTER(abd).abd_iovcnt = n;
        return (abd);
}

void
abd_free_struct_impl(abd_t *abd)
{
        /* For scatter, compute the extra amount we need to free */
        uint_t iovcnt =
            abd_is_linear(abd) || abd_is_gang(abd) ?
            0 : (ABD_SCATTER(abd).abd_iovcnt - 1);
        umem_free(abd, sizeof (abd_t) + iovcnt * sizeof (struct iovec));
}

void
abd_alloc_chunks(abd_t *abd, size_t size)
{
        /*
         * We've already allocated the iovec array; ensure that the wanted size
         * actually matches, otherwise the caller has made a mistake somewhere.
         */
        uint_t n = ABD_SCATTER(abd).abd_iovcnt;
        ASSERT3U(n, ==, abd_iovcnt_for_bytes(size));

        /*
         * Allocate a ABD_PAGESIZE region for each iovec.
         */
        struct iovec *iov = ABD_SCATTER(abd).abd_iov;
        for (int i = 0; i < n; i++) {
                iov[i].iov_base =
                    umem_alloc_aligned(ABD_PAGESIZE, ABD_PAGESIZE, UMEM_NOFAIL);
                iov[i].iov_len = ABD_PAGESIZE;
        }
}

void
abd_free_chunks(abd_t *abd)
{
        uint_t n = ABD_SCATTER(abd).abd_iovcnt;
        struct iovec *iov = ABD_SCATTER(abd).abd_iov;
        for (int i = 0; i < n; i++)
                umem_free_aligned(iov[i].iov_base, ABD_PAGESIZE);
}

boolean_t
abd_size_alloc_linear(size_t size)
{
        return (size < ABD_SCATTER_MIN_SIZE);
}

void
abd_update_scatter_stats(abd_t *abd, abd_stats_op_t op)
{
        ASSERT(op == ABDSTAT_INCR || op == ABDSTAT_DECR);
        int waste = P2ROUNDUP(abd->abd_size, ABD_PAGESIZE) - abd->abd_size;
        if (op == ABDSTAT_INCR) {
                arc_space_consume(waste, ARC_SPACE_ABD_CHUNK_WASTE);
        } else {
                arc_space_return(waste, ARC_SPACE_ABD_CHUNK_WASTE);
        }
}

void
abd_update_linear_stats(abd_t *abd, abd_stats_op_t op)
{
        (void) abd;
        (void) op;
        ASSERT(op == ABDSTAT_INCR || op == ABDSTAT_DECR);
}

void
abd_verify_scatter(abd_t *abd)
{
#ifdef ZFS_DEBUG
        /*
         * scatter abds shall have:
         * - at least one iovec
         * - all iov_base point somewhere
         * - all iov_len are ABD_PAGESIZE
         * - offset set within the abd pages somewhere
         */
        uint_t n = ABD_SCATTER(abd).abd_iovcnt;
        ASSERT3U(n, >, 0);

        uint_t len = 0;
        for (int i = 0; i < n; i++) {
                ASSERT3P(ABD_SCATTER(abd).abd_iov[i].iov_base, !=, NULL);
                ASSERT3U(ABD_SCATTER(abd).abd_iov[i].iov_len, ==, ABD_PAGESIZE);
                len += ABD_PAGESIZE;
        }

        ASSERT3U(ABD_SCATTER(abd).abd_offset, <, len);
#endif
}

void
abd_init(void)
{
        /*
         * Create the "zero" scatter abd. This is always the size of the
         * largest possible block, but only actually has a single allocated
         * page, which all iovecs in the abd point to.
         */
        abd_zero_scatter = abd_alloc_struct(SPA_MAXBLOCKSIZE);
        abd_zero_scatter->abd_flags |= ABD_FLAG_OWNER;
        abd_zero_scatter->abd_size = SPA_MAXBLOCKSIZE;

        void *zero =
            umem_alloc_aligned(ABD_PAGESIZE, ABD_PAGESIZE, UMEM_NOFAIL);
        memset(zero, 0, ABD_PAGESIZE);

        uint_t n = abd_iovcnt_for_bytes(SPA_MAXBLOCKSIZE);
        struct iovec *iov = ABD_SCATTER(abd_zero_scatter).abd_iov;
        for (int i = 0; i < n; i++) {
                iov[i].iov_base = zero;
                iov[i].iov_len = ABD_PAGESIZE;
        }
}

void
abd_fini(void)
{
        umem_free_aligned(
            ABD_SCATTER(abd_zero_scatter).abd_iov[0].iov_base, ABD_PAGESIZE);
        abd_free_struct(abd_zero_scatter);
        abd_zero_scatter = NULL;
}

void
abd_free_linear_page(abd_t *abd)
{
        /*
         * LINEAR_PAGE is specific to the Linux kernel; we never set this
         * flag, so this will never be called.
         */
        (void) abd;
        PANIC("unreachable");
}

abd_t *
abd_alloc_for_io(size_t size, boolean_t is_metadata)
{
        return (abd_alloc(size, is_metadata));
}

abd_t *
abd_get_offset_scatter(abd_t *dabd, abd_t *sabd, size_t off, size_t size)
{

        /*
         * Create a new scatter dabd by borrowing data pages from sabd to cover
         * off+size.
         *
         * sabd is an existing scatter abd with a set of iovecs, each covering
         * an ABD_PAGESIZE (4K) allocation. It's "zero" is at abd_offset.
         *
         *   [........][........][........][........]
         *      ^- sabd_offset
         *
         * We want to produce a new abd, referencing those allocations at the
         * given offset.
         *
         *   [........][........][........][........]
         *                    ^- dabd_offset = sabd_offset + off
         *                                        ^- dabd_offset + size
         *
         * In this example, dabd needs three iovecs. The first iovec is offset
         * 0, so the final dabd_offset is masked back into the first iovec.
         *
         *             [........][........][........]
         *                    ^- dabd_offset
         */
        size_t soff = ABD_SCATTER(sabd).abd_offset + off;
        size_t doff = soff & ABD_PAGEMASK;
        size_t iovcnt = abd_iovcnt_for_bytes(doff + size);

        /*
         * If the passed-in abd has enough allocated iovecs already, reuse it.
         * Otherwise, make a new one. The caller will free the original if the
         * one it gets back is not the same.
         *
         * Note that it's ok if we reuse an abd with more iovecs than we need.
         * abd_size has the usable amount of data, and the abd does not own the
         * pages referenced by the iovecs. At worst, they're holding dangling
         * pointers that we'll never use anyway.
         */
        if (dabd == NULL || ABD_SCATTER(dabd).abd_iovcnt < iovcnt)
                dabd = abd_alloc_struct(iovcnt << ABD_PAGESHIFT);

        /* Set offset into first page in view */
        ABD_SCATTER(dabd).abd_offset = doff;

        /* Copy the wanted iovecs from the source to the dest */
        memcpy(&ABD_SCATTER(dabd).abd_iov[0],
            &ABD_SCATTER(sabd).abd_iov[soff >> ABD_PAGESHIFT],
            iovcnt * sizeof (struct iovec));

        return (dabd);
}

void
abd_iter_init(struct abd_iter *aiter, abd_t *abd)
{
        ASSERT(!abd_is_gang(abd));
        abd_verify(abd);
        memset(aiter, 0, sizeof (struct abd_iter));
        aiter->iter_abd = abd;
}

boolean_t
abd_iter_at_end(struct abd_iter *aiter)
{
        ASSERT3U(aiter->iter_pos, <=, aiter->iter_abd->abd_size);
        return (aiter->iter_pos == aiter->iter_abd->abd_size);
}

void
abd_iter_advance(struct abd_iter *aiter, size_t amount)
{
        ASSERT3P(aiter->iter_mapaddr, ==, NULL);
        ASSERT0(aiter->iter_mapsize);

        if (abd_iter_at_end(aiter))
                return;

        aiter->iter_pos += amount;
        ASSERT3U(aiter->iter_pos, <=, aiter->iter_abd->abd_size);
}

void
abd_iter_map(struct abd_iter *aiter)
{
        ASSERT3P(aiter->iter_mapaddr, ==, NULL);
        ASSERT0(aiter->iter_mapsize);

        if (abd_iter_at_end(aiter))
                return;

        if (abd_is_linear(aiter->iter_abd)) {
                aiter->iter_mapaddr =
                    ABD_LINEAR_BUF(aiter->iter_abd) + aiter->iter_pos;
                aiter->iter_mapsize =
                    aiter->iter_abd->abd_size - aiter->iter_pos;
                return;
        }

        /*
         * For scatter, we index into the appropriate iovec, and return the
         * smaller of the amount requested, or up to the end of the page.
         */
        size_t poff = aiter->iter_pos + ABD_SCATTER(aiter->iter_abd).abd_offset;

        ASSERT3U(poff >> ABD_PAGESHIFT, <=,
            ABD_SCATTER(aiter->iter_abd).abd_iovcnt);
        struct iovec *iov = &ABD_SCATTER(aiter->iter_abd).
            abd_iov[poff >> ABD_PAGESHIFT];

        aiter->iter_mapsize = MIN(ABD_PAGESIZE - (poff & ABD_PAGEMASK),
            aiter->iter_abd->abd_size - aiter->iter_pos);
        ASSERT3U(aiter->iter_mapsize, <=, ABD_PAGESIZE);

        aiter->iter_mapaddr = iov->iov_base + (poff & ABD_PAGEMASK);
}

void
abd_iter_unmap(struct abd_iter *aiter)
{
        if (abd_iter_at_end(aiter))
                return;

        ASSERT3P(aiter->iter_mapaddr, !=, NULL);
        ASSERT3U(aiter->iter_mapsize, >, 0);

        aiter->iter_mapaddr = NULL;
        aiter->iter_mapsize = 0;
}

void
abd_cache_reap_now(void)
{
}

/*
 * Borrow a raw buffer from an ABD without copying the contents of the ABD
 * into the buffer. If the ABD is scattered, this will alloate 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, >=, 0);
        if (abd_is_linear(abd)) {
                buf = abd_to_buf(abd);
        } else {
                buf = zio_buf_alloc(n);
        }
#ifdef ZFS_DEBUG
        (void) zfs_refcount_add_many(&abd->abd_children, n, buf);
#endif
        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
 * no 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);
#ifdef ZFS_DEBUG
        (void) zfs_refcount_remove_many(&abd->abd_children, n, buf);
#endif
        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
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);
}