/*
 * Copyright (C) 2003 Sistina Software
 * Copyright (C) 2006 Red Hat GmbH
 *
 * This file is released under the GPL.
 */

#include "dm-core.h"

#include <linux/device-mapper.h>

#include <linux/bio.h>
#include <linux/completion.h>
#include <linux/mempool.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/dm-io.h>

#define DM_MSG_PREFIX "io"

#define DM_IO_MAX_REGIONS       BITS_PER_LONG

struct dm_io_client {
        mempool_t *pool;
        struct bio_set *bios;
};

/*
 * Aligning 'struct io' reduces the number of bits required to store
 * its address.  Refer to store_io_and_region_in_bio() below.
 */
struct io {
        unsigned long error_bits;
        atomic_t count;
        struct dm_io_client *client;
        io_notify_fn callback;
        void *context;
        void *vma_invalidate_address;
        unsigned long vma_invalidate_size;
} __attribute__((aligned(DM_IO_MAX_REGIONS)));

static struct kmem_cache *_dm_io_cache;

/*
 * Create a client with mempool and bioset.
 */
struct dm_io_client *dm_io_client_create(void)
{
        struct dm_io_client *client;
        unsigned min_ios = dm_get_reserved_bio_based_ios();

        client = kmalloc(sizeof(*client), GFP_KERNEL);
        if (!client)
                return ERR_PTR(-ENOMEM);

        client->pool = mempool_create_slab_pool(min_ios, _dm_io_cache);
        if (!client->pool)
                goto bad;

        client->bios = bioset_create(min_ios, 0, (BIOSET_NEED_BVECS |
                                                  BIOSET_NEED_RESCUER));
        if (!client->bios)
                goto bad;

        return client;

   bad:
        mempool_destroy(client->pool);
        kfree(client);
        return ERR_PTR(-ENOMEM);
}
EXPORT_SYMBOL(dm_io_client_create);

void dm_io_client_destroy(struct dm_io_client *client)
{
        mempool_destroy(client->pool);
        bioset_free(client->bios);
        kfree(client);
}
EXPORT_SYMBOL(dm_io_client_destroy);

/*-----------------------------------------------------------------
 * We need to keep track of which region a bio is doing io for.
 * To avoid a memory allocation to store just 5 or 6 bits, we
 * ensure the 'struct io' pointer is aligned so enough low bits are
 * always zero and then combine it with the region number directly in
 * bi_private.
 *---------------------------------------------------------------*/
static void store_io_and_region_in_bio(struct bio *bio, struct io *io,
                                       unsigned region)
{
        if (unlikely(!IS_ALIGNED((unsigned long)io, DM_IO_MAX_REGIONS))) {
                DMCRIT("Unaligned struct io pointer %p", io);
                BUG();
        }

        bio->bi_private = (void *)((unsigned long)io | region);
}

static void retrieve_io_and_region_from_bio(struct bio *bio, struct io **io,
                                       unsigned *region)
{
        unsigned long val = (unsigned long)bio->bi_private;

        *io = (void *)(val & -(unsigned long)DM_IO_MAX_REGIONS);
        *region = val & (DM_IO_MAX_REGIONS - 1);
}

/*-----------------------------------------------------------------
 * We need an io object to keep track of the number of bios that
 * have been dispatched for a particular io.
 *---------------------------------------------------------------*/
static void complete_io(struct io *io)
{
        unsigned long error_bits = io->error_bits;
        io_notify_fn fn = io->callback;
        void *context = io->context;

        if (io->vma_invalidate_size)
                invalidate_kernel_vmap_range(io->vma_invalidate_address,
                                             io->vma_invalidate_size);

        mempool_free(io, io->client->pool);
        fn(error_bits, context);
}

static void dec_count(struct io *io, unsigned int region, blk_status_t error)
{
        if (error)
                set_bit(region, &io->error_bits);

        if (atomic_dec_and_test(&io->count))
                complete_io(io);
}

static void endio(struct bio *bio)
{
        struct io *io;
        unsigned region;
        blk_status_t error;

        if (bio->bi_status && bio_data_dir(bio) == READ)
                zero_fill_bio(bio);

        /*
         * The bio destructor in bio_put() may use the io object.
         */
        retrieve_io_and_region_from_bio(bio, &io, &region);

        error = bio->bi_status;
        bio_put(bio);

        dec_count(io, region, error);
}

/*-----------------------------------------------------------------
 * These little objects provide an abstraction for getting a new
 * destination page for io.
 *---------------------------------------------------------------*/
struct dpages {
        void (*get_page)(struct dpages *dp,
                         struct page **p, unsigned long *len, unsigned *offset);
        void (*next_page)(struct dpages *dp);

        union {
                unsigned context_u;
                struct bvec_iter context_bi;
        };
        void *context_ptr;

        void *vma_invalidate_address;
        unsigned long vma_invalidate_size;
};

/*
 * Functions for getting the pages from a list.
 */
static void list_get_page(struct dpages *dp,
                  struct page **p, unsigned long *len, unsigned *offset)
{
        unsigned o = dp->context_u;
        struct page_list *pl = (struct page_list *) dp->context_ptr;

        *p = pl->page;
        *len = PAGE_SIZE - o;
        *offset = o;
}

static void list_next_page(struct dpages *dp)
{
        struct page_list *pl = (struct page_list *) dp->context_ptr;
        dp->context_ptr = pl->next;
        dp->context_u = 0;
}

static void list_dp_init(struct dpages *dp, struct page_list *pl, unsigned offset)
{
        dp->get_page = list_get_page;
        dp->next_page = list_next_page;
        dp->context_u = offset;
        dp->context_ptr = pl;
}

/*
 * Functions for getting the pages from a bvec.
 */
static void bio_get_page(struct dpages *dp, struct page **p,
                         unsigned long *len, unsigned *offset)
{
        struct bio_vec bvec = bvec_iter_bvec((struct bio_vec *)dp->context_ptr,
                                             dp->context_bi);

        *p = bvec.bv_page;
        *len = bvec.bv_len;
        *offset = bvec.bv_offset;

        /* avoid figuring it out again in bio_next_page() */
        dp->context_bi.bi_sector = (sector_t)bvec.bv_len;
}

static void bio_next_page(struct dpages *dp)
{
        unsigned int len = (unsigned int)dp->context_bi.bi_sector;

        bvec_iter_advance((struct bio_vec *)dp->context_ptr,
                          &dp->context_bi, len);
}

static void bio_dp_init(struct dpages *dp, struct bio *bio)
{
        dp->get_page = bio_get_page;
        dp->next_page = bio_next_page;

        /*
         * We just use bvec iterator to retrieve pages, so it is ok to
         * access the bvec table directly here
         */
        dp->context_ptr = bio->bi_io_vec;
        dp->context_bi = bio->bi_iter;
}

/*
 * Functions for getting the pages from a VMA.
 */
static void vm_get_page(struct dpages *dp,
                 struct page **p, unsigned long *len, unsigned *offset)
{
        *p = vmalloc_to_page(dp->context_ptr);
        *offset = dp->context_u;
        *len = PAGE_SIZE - dp->context_u;
}

static void vm_next_page(struct dpages *dp)
{
        dp->context_ptr += PAGE_SIZE - dp->context_u;
        dp->context_u = 0;
}

static void vm_dp_init(struct dpages *dp, void *data)
{
        dp->get_page = vm_get_page;
        dp->next_page = vm_next_page;
        dp->context_u = offset_in_page(data);
        dp->context_ptr = data;
}

/*
 * Functions for getting the pages from kernel memory.
 */
static void km_get_page(struct dpages *dp, struct page **p, unsigned long *len,
                        unsigned *offset)
{
        *p = virt_to_page(dp->context_ptr);
        *offset = dp->context_u;
        *len = PAGE_SIZE - dp->context_u;
}

static void km_next_page(struct dpages *dp)
{
        dp->context_ptr += PAGE_SIZE - dp->context_u;
        dp->context_u = 0;
}

static void km_dp_init(struct dpages *dp, void *data)
{
        dp->get_page = km_get_page;
        dp->next_page = km_next_page;
        dp->context_u = offset_in_page(data);
        dp->context_ptr = data;
}

/*-----------------------------------------------------------------
 * IO routines that accept a list of pages.
 *---------------------------------------------------------------*/
static void do_region(int op, int op_flags, unsigned region,
                      struct dm_io_region *where, struct dpages *dp,
                      struct io *io)
{
        struct bio *bio;
        struct page *page;
        unsigned long len;
        unsigned offset;
        unsigned num_bvecs;
        sector_t remaining = where->count;
        struct request_queue *q = bdev_get_queue(where->bdev);
        unsigned short logical_block_size = queue_logical_block_size(q);
        sector_t num_sectors;
        unsigned int uninitialized_var(special_cmd_max_sectors);

        /*
         * Reject unsupported discard and write same requests.
         */
        if (op == REQ_OP_DISCARD)
                special_cmd_max_sectors = q->limits.max_discard_sectors;
        else if (op == REQ_OP_WRITE_ZEROES)
                special_cmd_max_sectors = q->limits.max_write_zeroes_sectors;
        else if (op == REQ_OP_WRITE_SAME)
                special_cmd_max_sectors = q->limits.max_write_same_sectors;
        if ((op == REQ_OP_DISCARD || op == REQ_OP_WRITE_ZEROES ||
             op == REQ_OP_WRITE_SAME) && special_cmd_max_sectors == 0) {
                atomic_inc(&io->count);
                dec_count(io, region, BLK_STS_NOTSUPP);
                return;
        }

        /*
         * where->count may be zero if op holds a flush and we need to
         * send a zero-sized flush.
         */
        do {
                /*
                 * Allocate a suitably sized-bio.
                 */
                switch (op) {
                case REQ_OP_DISCARD:
                case REQ_OP_WRITE_ZEROES:
                        num_bvecs = 0;
                        break;
                case REQ_OP_WRITE_SAME:
                        num_bvecs = 1;
                        break;
                default:
                        num_bvecs = min_t(int, BIO_MAX_PAGES,
                                          dm_sector_div_up(remaining, (PAGE_SIZE >> SECTOR_SHIFT)));
                }

                bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, io->client->bios);
                bio->bi_iter.bi_sector = where->sector + (where->count - remaining);
                bio_set_dev(bio, where->bdev);
                bio->bi_end_io = endio;
                bio_set_op_attrs(bio, op, op_flags);
                store_io_and_region_in_bio(bio, io, region);

                if (op == REQ_OP_DISCARD || op == REQ_OP_WRITE_ZEROES) {
                        num_sectors = min_t(sector_t, special_cmd_max_sectors, remaining);
                        bio->bi_iter.bi_size = num_sectors << SECTOR_SHIFT;
                        remaining -= num_sectors;
                } else if (op == REQ_OP_WRITE_SAME) {
                        /*
                         * WRITE SAME only uses a single page.
                         */
                        dp->get_page(dp, &page, &len, &offset);
                        bio_add_page(bio, page, logical_block_size, offset);
                        num_sectors = min_t(sector_t, special_cmd_max_sectors, remaining);
                        bio->bi_iter.bi_size = num_sectors << SECTOR_SHIFT;

                        offset = 0;
                        remaining -= num_sectors;
                        dp->next_page(dp);
                } else while (remaining) {
                        /*
                         * Try and add as many pages as possible.
                         */
                        dp->get_page(dp, &page, &len, &offset);
                        len = min(len, to_bytes(remaining));
                        if (!bio_add_page(bio, page, len, offset))
                                break;

                        offset = 0;
                        remaining -= to_sector(len);
                        dp->next_page(dp);
                }

                atomic_inc(&io->count);
                submit_bio(bio);
        } while (remaining);
}

static void dispatch_io(int op, int op_flags, unsigned int num_regions,
                        struct dm_io_region *where, struct dpages *dp,
                        struct io *io, int sync)
{
        int i;
        struct dpages old_pages = *dp;

        BUG_ON(num_regions > DM_IO_MAX_REGIONS);

        if (sync)
                op_flags |= REQ_SYNC;

        /*
         * For multiple regions we need to be careful to rewind
         * the dp object for each call to do_region.
         */
        for (i = 0; i < num_regions; i++) {
                *dp = old_pages;
                if (where[i].count || (op_flags & REQ_PREFLUSH))
                        do_region(op, op_flags, i, where + i, dp, io);
        }

        /*
         * Drop the extra reference that we were holding to avoid
         * the io being completed too early.
         */
        dec_count(io, 0, 0);
}

struct sync_io {
        unsigned long error_bits;
        struct completion wait;
};

static void sync_io_complete(unsigned long error, void *context)
{
        struct sync_io *sio = context;

        sio->error_bits = error;
        complete(&sio->wait);
}

static int sync_io(struct dm_io_client *client, unsigned int num_regions,
                   struct dm_io_region *where, int op, int op_flags,
                   struct dpages *dp, unsigned long *error_bits)
{
        struct io *io;
        struct sync_io sio;

        if (num_regions > 1 && !op_is_write(op)) {
                WARN_ON(1);
                return -EIO;
        }

        init_completion(&sio.wait);

        io = mempool_alloc(client->pool, GFP_NOIO);
        io->error_bits = 0;
        atomic_set(&io->count, 1); /* see dispatch_io() */
        io->client = client;
        io->callback = sync_io_complete;
        io->context = &sio;

        io->vma_invalidate_address = dp->vma_invalidate_address;
        io->vma_invalidate_size = dp->vma_invalidate_size;

        dispatch_io(op, op_flags, num_regions, where, dp, io, 1);

        wait_for_completion_io(&sio.wait);

        if (error_bits)
                *error_bits = sio.error_bits;

        return sio.error_bits ? -EIO : 0;
}

static int async_io(struct dm_io_client *client, unsigned int num_regions,
                    struct dm_io_region *where, int op, int op_flags,
                    struct dpages *dp, io_notify_fn fn, void *context)
{
        struct io *io;

        if (num_regions > 1 && !op_is_write(op)) {
                WARN_ON(1);
                fn(1, context);
                return -EIO;
        }

        io = mempool_alloc(client->pool, GFP_NOIO);
        io->error_bits = 0;
        atomic_set(&io->count, 1); /* see dispatch_io() */
        io->client = client;
        io->callback = fn;
        io->context = context;

        io->vma_invalidate_address = dp->vma_invalidate_address;
        io->vma_invalidate_size = dp->vma_invalidate_size;

        dispatch_io(op, op_flags, num_regions, where, dp, io, 0);
        return 0;
}

static int dp_init(struct dm_io_request *io_req, struct dpages *dp,
                   unsigned long size)
{
        /* Set up dpages based on memory type */

        dp->vma_invalidate_address = NULL;
        dp->vma_invalidate_size = 0;

        switch (io_req->mem.type) {
        case DM_IO_PAGE_LIST:
                list_dp_init(dp, io_req->mem.ptr.pl, io_req->mem.offset);
                break;

        case DM_IO_BIO:
                bio_dp_init(dp, io_req->mem.ptr.bio);
                break;

        case DM_IO_VMA:
                flush_kernel_vmap_range(io_req->mem.ptr.vma, size);
                if (io_req->bi_op == REQ_OP_READ) {
                        dp->vma_invalidate_address = io_req->mem.ptr.vma;
                        dp->vma_invalidate_size = size;
                }
                vm_dp_init(dp, io_req->mem.ptr.vma);
                break;

        case DM_IO_KMEM:
                km_dp_init(dp, io_req->mem.ptr.addr);
                break;

        default:
                return -EINVAL;
        }

        return 0;
}

/*
 * New collapsed (a)synchronous interface.
 *
 * If the IO is asynchronous (i.e. it has notify.fn), you must either unplug
 * the queue with blk_unplug() some time later or set REQ_SYNC in
 * io_req->bi_opf. If you fail to do one of these, the IO will be submitted to
 * the disk after q->unplug_delay, which defaults to 3ms in blk-settings.c.
 */
int dm_io(struct dm_io_request *io_req, unsigned num_regions,
          struct dm_io_region *where, unsigned long *sync_error_bits)
{
        int r;
        struct dpages dp;

        r = dp_init(io_req, &dp, (unsigned long)where->count << SECTOR_SHIFT);
        if (r)
                return r;

        if (!io_req->notify.fn)
                return sync_io(io_req->client, num_regions, where,
                               io_req->bi_op, io_req->bi_op_flags, &dp,
                               sync_error_bits);

        return async_io(io_req->client, num_regions, where, io_req->bi_op,
                        io_req->bi_op_flags, &dp, io_req->notify.fn,
                        io_req->notify.context);
}
EXPORT_SYMBOL(dm_io);

int __init dm_io_init(void)
{
        _dm_io_cache = KMEM_CACHE(io, 0);
        if (!_dm_io_cache)
                return -ENOMEM;

        return 0;
}

void dm_io_exit(void)
{
        kmem_cache_destroy(_dm_io_cache);
        _dm_io_cache = NULL;
}