// SPDX-License-Identifier: GPL-2.0
/* bounce buffer handling for block devices
 *
 * - Split from highmem.c
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/mm.h>
#include <linux/export.h>
#include <linux/swap.h>
#include <linux/gfp.h>
#include <linux/bio.h>
#include <linux/pagemap.h>
#include <linux/mempool.h>
#include <linux/blkdev.h>
#include <linux/backing-dev.h>
#include <linux/init.h>
#include <linux/hash.h>
#include <linux/highmem.h>
#include <linux/printk.h>
#include <asm/tlbflush.h>

#include <trace/events/block.h>
#include "blk.h"

#define POOL_SIZE       64
#define ISA_POOL_SIZE   16

static struct bio_set bounce_bio_set, bounce_bio_split;
static mempool_t page_pool;

static void init_bounce_bioset(void)
{
        static bool bounce_bs_setup;
        int ret;

        if (bounce_bs_setup)
                return;

        ret = bioset_init(&bounce_bio_set, BIO_POOL_SIZE, 0, BIOSET_NEED_BVECS);
        BUG_ON(ret);
        if (bioset_integrity_create(&bounce_bio_set, BIO_POOL_SIZE))
                BUG_ON(1);

        ret = bioset_init(&bounce_bio_split, BIO_POOL_SIZE, 0, 0);
        BUG_ON(ret);
        bounce_bs_setup = true;
}

static __init int init_emergency_pool(void)
{
        int ret;

#ifndef CONFIG_MEMORY_HOTPLUG
        if (max_pfn <= max_low_pfn)
                return 0;
#endif

        ret = mempool_init_page_pool(&page_pool, POOL_SIZE, 0);
        BUG_ON(ret);
        pr_info("pool size: %d pages\n", POOL_SIZE);

        init_bounce_bioset();
        return 0;
}

__initcall(init_emergency_pool);

/*
 * Simple bounce buffer support for highmem pages. Depending on the
 * queue gfp mask set, *to may or may not be a highmem page. kmap it
 * always, it will do the Right Thing
 */
static void copy_to_high_bio_irq(struct bio *to, struct bio *from)
{
        struct bio_vec tovec, fromvec;
        struct bvec_iter iter;
        /*
         * The bio of @from is created by bounce, so we can iterate
         * its bvec from start to end, but the @from->bi_iter can't be
         * trusted because it might be changed by splitting.
         */
        struct bvec_iter from_iter = BVEC_ITER_ALL_INIT;

        bio_for_each_segment(tovec, to, iter) {
                fromvec = bio_iter_iovec(from, from_iter);
                if (tovec.bv_page != fromvec.bv_page) {
                        /*
                         * fromvec->bv_offset and fromvec->bv_len might have
                         * been modified by the block layer, so use the original
                         * copy, bounce_copy_vec already uses tovec->bv_len
                         */
                        memcpy_to_bvec(&tovec, page_address(fromvec.bv_page) +
                                       tovec.bv_offset);
                }
                bio_advance_iter(from, &from_iter, tovec.bv_len);
        }
}

static void bounce_end_io(struct bio *bio)
{
        struct bio *bio_orig = bio->bi_private;
        struct bio_vec *bvec, orig_vec;
        struct bvec_iter orig_iter = bio_orig->bi_iter;
        struct bvec_iter_all iter_all;

        /*
         * free up bounce indirect pages used
         */
        bio_for_each_segment_all(bvec, bio, iter_all) {
                orig_vec = bio_iter_iovec(bio_orig, orig_iter);
                if (bvec->bv_page != orig_vec.bv_page) {
                        dec_zone_page_state(bvec->bv_page, NR_BOUNCE);
                        mempool_free(bvec->bv_page, &page_pool);
                }
                bio_advance_iter(bio_orig, &orig_iter, orig_vec.bv_len);
        }

        bio_orig->bi_status = bio->bi_status;
        bio_endio(bio_orig);
        bio_put(bio);
}

static void bounce_end_io_write(struct bio *bio)
{
        bounce_end_io(bio);
}

static void bounce_end_io_read(struct bio *bio)
{
        struct bio *bio_orig = bio->bi_private;

        if (!bio->bi_status)
                copy_to_high_bio_irq(bio_orig, bio);

        bounce_end_io(bio);
}

static struct bio *bounce_clone_bio(struct bio *bio_src)
{
        struct bvec_iter iter;
        struct bio_vec bv;
        struct bio *bio;

        /*
         * Pre immutable biovecs, __bio_clone() used to just do a memcpy from
         * bio_src->bi_io_vec to bio->bi_io_vec.
         *
         * We can't do that anymore, because:
         *
         *  - The point of cloning the biovec is to produce a bio with a biovec
         *    the caller can modify: bi_idx and bi_bvec_done should be 0.
         *
         *  - The original bio could've had more than BIO_MAX_VECS biovecs; if
         *    we tried to clone the whole thing bio_alloc_bioset() would fail.
         *    But the clone should succeed as long as the number of biovecs we
         *    actually need to allocate is fewer than BIO_MAX_VECS.
         *
         *  - Lastly, bi_vcnt should not be looked at or relied upon by code
         *    that does not own the bio - reason being drivers don't use it for
         *    iterating over the biovec anymore, so expecting it to be kept up
         *    to date (i.e. for clones that share the parent biovec) is just
         *    asking for trouble and would force extra work on
         *    __bio_clone_fast() anyways.
         */
        bio = bio_alloc_bioset(GFP_NOIO, bio_segments(bio_src),
                               &bounce_bio_set);
        bio->bi_bdev            = bio_src->bi_bdev;
        if (bio_flagged(bio_src, BIO_REMAPPED))
                bio_set_flag(bio, BIO_REMAPPED);
        bio->bi_opf             = bio_src->bi_opf;
        bio->bi_ioprio          = bio_src->bi_ioprio;
        bio->bi_write_hint      = bio_src->bi_write_hint;
        bio->bi_iter.bi_sector  = bio_src->bi_iter.bi_sector;
        bio->bi_iter.bi_size    = bio_src->bi_iter.bi_size;

        switch (bio_op(bio)) {
        case REQ_OP_DISCARD:
        case REQ_OP_SECURE_ERASE:
        case REQ_OP_WRITE_ZEROES:
                break;
        case REQ_OP_WRITE_SAME:
                bio->bi_io_vec[bio->bi_vcnt++] = bio_src->bi_io_vec[0];
                break;
        default:
                bio_for_each_segment(bv, bio_src, iter)
                        bio->bi_io_vec[bio->bi_vcnt++] = bv;
                break;
        }

        if (bio_crypt_clone(bio, bio_src, GFP_NOIO) < 0)
                goto err_put;

        if (bio_integrity(bio_src) &&
            bio_integrity_clone(bio, bio_src, GFP_NOIO) < 0)
                goto err_put;

        bio_clone_blkg_association(bio, bio_src);
        blkcg_bio_issue_init(bio);

        return bio;

err_put:
        bio_put(bio);
        return NULL;
}

void __blk_queue_bounce(struct request_queue *q, struct bio **bio_orig)
{
        struct bio *bio;
        int rw = bio_data_dir(*bio_orig);
        struct bio_vec *to, from;
        struct bvec_iter iter;
        unsigned i = 0;
        bool bounce = false;
        int sectors = 0;

        bio_for_each_segment(from, *bio_orig, iter) {
                if (i++ < BIO_MAX_VECS)
                        sectors += from.bv_len >> 9;
                if (PageHighMem(from.bv_page))
                        bounce = true;
        }
        if (!bounce)
                return;

        if (sectors < bio_sectors(*bio_orig)) {
                bio = bio_split(*bio_orig, sectors, GFP_NOIO, &bounce_bio_split);
                bio_chain(bio, *bio_orig);
                submit_bio_noacct(*bio_orig);
                *bio_orig = bio;
        }
        bio = bounce_clone_bio(*bio_orig);

        /*
         * Bvec table can't be updated by bio_for_each_segment_all(),
         * so retrieve bvec from the table directly. This way is safe
         * because the 'bio' is single-page bvec.
         */
        for (i = 0, to = bio->bi_io_vec; i < bio->bi_vcnt; to++, i++) {
                struct page *bounce_page;

                if (!PageHighMem(to->bv_page))
                        continue;

                bounce_page = mempool_alloc(&page_pool, GFP_NOIO);
                inc_zone_page_state(bounce_page, NR_BOUNCE);

                if (rw == WRITE) {
                        flush_dcache_page(to->bv_page);
                        memcpy_from_bvec(page_address(bounce_page), to);
                }
                to->bv_page = bounce_page;
        }

        trace_block_bio_bounce(*bio_orig);

        bio->bi_flags |= (1 << BIO_BOUNCED);

        if (rw == READ)
                bio->bi_end_io = bounce_end_io_read;
        else
                bio->bi_end_io = bounce_end_io_write;

        bio->bi_private = *bio_orig;
        *bio_orig = bio;
}