/*
 * bio-integrity.c - bio data integrity extensions
 *
 * Copyright (C) 2007, 2008, 2009 Oracle Corporation
 * Written by: Martin K. Petersen <martin.petersen@oracle.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version
 * 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; see the file COPYING.  If not, write to
 * the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139,
 * USA.
 *
 */

#include <linux/blkdev.h>
#include <linux/mempool.h>
#include <linux/export.h>
#include <linux/bio.h>
#include <linux/workqueue.h>
#include <linux/slab.h>
#include "blk.h"

#define BIP_INLINE_VECS 4

static struct kmem_cache *bip_slab;
static struct workqueue_struct *kintegrityd_wq;

void blk_flush_integrity(void)
{
        flush_workqueue(kintegrityd_wq);
}

/**
 * bio_integrity_alloc - Allocate integrity payload and attach it to bio
 * @bio:        bio to attach integrity metadata to
 * @gfp_mask:   Memory allocation mask
 * @nr_vecs:    Number of integrity metadata scatter-gather elements
 *
 * Description: This function prepares a bio for attaching integrity
 * metadata.  nr_vecs specifies the maximum number of pages containing
 * integrity metadata that can be attached.
 */
struct bio_integrity_payload *bio_integrity_alloc(struct bio *bio,
                                                  gfp_t gfp_mask,
                                                  unsigned int nr_vecs)
{
        struct bio_integrity_payload *bip;
        struct bio_set *bs = bio->bi_pool;
        unsigned inline_vecs;

        if (!bs || !bs->bio_integrity_pool) {
                bip = kmalloc(sizeof(struct bio_integrity_payload) +
                              sizeof(struct bio_vec) * nr_vecs, gfp_mask);
                inline_vecs = nr_vecs;
        } else {
                bip = mempool_alloc(bs->bio_integrity_pool, gfp_mask);
                inline_vecs = BIP_INLINE_VECS;
        }

        if (unlikely(!bip))
                return ERR_PTR(-ENOMEM);

        memset(bip, 0, sizeof(*bip));

        if (nr_vecs > inline_vecs) {
                unsigned long idx = 0;

                bip->bip_vec = bvec_alloc(gfp_mask, nr_vecs, &idx,
                                          bs->bvec_integrity_pool);
                if (!bip->bip_vec)
                        goto err;
                bip->bip_max_vcnt = bvec_nr_vecs(idx);
                bip->bip_slab = idx;
        } else {
                bip->bip_vec = bip->bip_inline_vecs;
                bip->bip_max_vcnt = inline_vecs;
        }

        bip->bip_bio = bio;
        bio->bi_integrity = bip;
        bio->bi_opf |= REQ_INTEGRITY;

        return bip;
err:
        mempool_free(bip, bs->bio_integrity_pool);
        return ERR_PTR(-ENOMEM);
}
EXPORT_SYMBOL(bio_integrity_alloc);

/**
 * bio_integrity_free - Free bio integrity payload
 * @bio:        bio containing bip to be freed
 *
 * Description: Used to free the integrity portion of a bio. Usually
 * called from bio_free().
 */
void bio_integrity_free(struct bio *bio)
{
        struct bio_integrity_payload *bip = bio_integrity(bio);
        struct bio_set *bs = bio->bi_pool;

        if (bip->bip_flags & BIP_BLOCK_INTEGRITY)
                kfree(page_address(bip->bip_vec->bv_page) +
                      bip->bip_vec->bv_offset);

        if (bs && bs->bio_integrity_pool) {
                bvec_free(bs->bvec_integrity_pool, bip->bip_vec, bip->bip_slab);

                mempool_free(bip, bs->bio_integrity_pool);
        } else {
                kfree(bip);
        }

        bio->bi_integrity = NULL;
}
EXPORT_SYMBOL(bio_integrity_free);

/**
 * bio_integrity_add_page - Attach integrity metadata
 * @bio:        bio to update
 * @page:       page containing integrity metadata
 * @len:        number of bytes of integrity metadata in page
 * @offset:     start offset within page
 *
 * Description: Attach a page containing integrity metadata to bio.
 */
int bio_integrity_add_page(struct bio *bio, struct page *page,
                           unsigned int len, unsigned int offset)
{
        struct bio_integrity_payload *bip = bio_integrity(bio);
        struct bio_vec *iv;

        if (bip->bip_vcnt >= bip->bip_max_vcnt) {
                printk(KERN_ERR "%s: bip_vec full\n", __func__);
                return 0;
        }

        iv = bip->bip_vec + bip->bip_vcnt;

        if (bip->bip_vcnt &&
            bvec_gap_to_prev(bdev_get_queue(bio->bi_bdev),
                             &bip->bip_vec[bip->bip_vcnt - 1], offset))
                return 0;

        iv->bv_page = page;
        iv->bv_len = len;
        iv->bv_offset = offset;
        bip->bip_vcnt++;

        return len;
}
EXPORT_SYMBOL(bio_integrity_add_page);

/**
 * bio_integrity_enabled - Check whether integrity can be passed
 * @bio:        bio to check
 *
 * Description: Determines whether bio_integrity_prep() can be called
 * on this bio or not.  bio data direction and target device must be
 * set prior to calling.  The functions honors the write_generate and
 * read_verify flags in sysfs.
 */
bool bio_integrity_enabled(struct bio *bio)
{
        struct blk_integrity *bi = bdev_get_integrity(bio->bi_bdev);

        if (!bio_is_rw(bio))
                return false;

        /* Already protected? */
        if (bio_integrity(bio))
                return false;

        if (bi == NULL)
                return false;

        if (bio_data_dir(bio) == READ && bi->profile->verify_fn != NULL &&
            (bi->flags & BLK_INTEGRITY_VERIFY))
                return true;

        if (bio_data_dir(bio) == WRITE && bi->profile->generate_fn != NULL &&
            (bi->flags & BLK_INTEGRITY_GENERATE))
                return true;

        return false;
}
EXPORT_SYMBOL(bio_integrity_enabled);

/**
 * bio_integrity_intervals - Return number of integrity intervals for a bio
 * @bi:         blk_integrity profile for device
 * @sectors:    Size of the bio in 512-byte sectors
 *
 * Description: The block layer calculates everything in 512 byte
 * sectors but integrity metadata is done in terms of the data integrity
 * interval size of the storage device.  Convert the block layer sectors
 * to the appropriate number of integrity intervals.
 */
static inline unsigned int bio_integrity_intervals(struct blk_integrity *bi,
                                                   unsigned int sectors)
{
        return sectors >> (bi->interval_exp - 9);
}

static inline unsigned int bio_integrity_bytes(struct blk_integrity *bi,
                                               unsigned int sectors)
{
        return bio_integrity_intervals(bi, sectors) * bi->tuple_size;
}

/**
 * bio_integrity_process - Process integrity metadata for a bio
 * @bio:        bio to generate/verify integrity metadata for
 * @proc_fn:    Pointer to the relevant processing function
 */
static int bio_integrity_process(struct bio *bio,
                                 integrity_processing_fn *proc_fn)
{
        struct blk_integrity *bi = bdev_get_integrity(bio->bi_bdev);
        struct blk_integrity_iter iter;
        struct bvec_iter bviter;
        struct bio_vec bv;
        struct bio_integrity_payload *bip = bio_integrity(bio);
        unsigned int ret = 0;
        void *prot_buf = page_address(bip->bip_vec->bv_page) +
                bip->bip_vec->bv_offset;

        iter.disk_name = bio->bi_bdev->bd_disk->disk_name;
        iter.interval = 1 << bi->interval_exp;
        iter.seed = bip_get_seed(bip);
        iter.prot_buf = prot_buf;

        bio_for_each_segment(bv, bio, bviter) {
                void *kaddr = kmap_atomic(bv.bv_page);

                iter.data_buf = kaddr + bv.bv_offset;
                iter.data_size = bv.bv_len;

                ret = proc_fn(&iter);
                if (ret) {
                        kunmap_atomic(kaddr);
                        return ret;
                }

                kunmap_atomic(kaddr);
        }
        return ret;
}

/**
 * bio_integrity_prep - Prepare bio for integrity I/O
 * @bio:        bio to prepare
 *
 * Description: Allocates a buffer for integrity metadata, maps the
 * pages and attaches them to a bio.  The bio must have data
 * direction, target device and start sector set priot to calling.  In
 * the WRITE case, integrity metadata will be generated using the
 * block device's integrity function.  In the READ case, the buffer
 * will be prepared for DMA and a suitable end_io handler set up.
 */
int bio_integrity_prep(struct bio *bio)
{
        struct bio_integrity_payload *bip;
        struct blk_integrity *bi;
        struct request_queue *q;
        void *buf;
        unsigned long start, end;
        unsigned int len, nr_pages;
        unsigned int bytes, offset, i;
        unsigned int intervals;

        bi = bdev_get_integrity(bio->bi_bdev);
        q = bdev_get_queue(bio->bi_bdev);
        BUG_ON(bi == NULL);
        BUG_ON(bio_integrity(bio));

        intervals = bio_integrity_intervals(bi, bio_sectors(bio));

        /* Allocate kernel buffer for protection data */
        len = intervals * bi->tuple_size;
        buf = kmalloc(len, GFP_NOIO | q->bounce_gfp);
        if (unlikely(buf == NULL)) {
                printk(KERN_ERR "could not allocate integrity buffer\n");
                return -ENOMEM;
        }

        end = (((unsigned long) buf) + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
        start = ((unsigned long) buf) >> PAGE_SHIFT;
        nr_pages = end - start;

        /* Allocate bio integrity payload and integrity vectors */
        bip = bio_integrity_alloc(bio, GFP_NOIO, nr_pages);
        if (IS_ERR(bip)) {
                printk(KERN_ERR "could not allocate data integrity bioset\n");
                kfree(buf);
                return PTR_ERR(bip);
        }

        bip->bip_flags |= BIP_BLOCK_INTEGRITY;
        bip->bip_iter.bi_size = len;
        bip_set_seed(bip, bio->bi_iter.bi_sector);

        if (bi->flags & BLK_INTEGRITY_IP_CHECKSUM)
                bip->bip_flags |= BIP_IP_CHECKSUM;

        /* Map it */
        offset = offset_in_page(buf);
        for (i = 0 ; i < nr_pages ; i++) {
                int ret;
                bytes = PAGE_SIZE - offset;

                if (len <= 0)
                        break;

                if (bytes > len)
                        bytes = len;

                ret = bio_integrity_add_page(bio, virt_to_page(buf),
                                             bytes, offset);

                if (ret == 0)
                        return 0;

                if (ret < bytes)
                        break;

                buf += bytes;
                len -= bytes;
                offset = 0;
        }

        /* Install custom I/O completion handler if read verify is enabled */
        if (bio_data_dir(bio) == READ) {
                bip->bip_end_io = bio->bi_end_io;
                bio->bi_end_io = bio_integrity_endio;
        }

        /* Auto-generate integrity metadata if this is a write */
        if (bio_data_dir(bio) == WRITE)
                bio_integrity_process(bio, bi->profile->generate_fn);

        return 0;
}
EXPORT_SYMBOL(bio_integrity_prep);

/**
 * bio_integrity_verify_fn - Integrity I/O completion worker
 * @work:       Work struct stored in bio to be verified
 *
 * Description: This workqueue function is called to complete a READ
 * request.  The function verifies the transferred integrity metadata
 * and then calls the original bio end_io function.
 */
static void bio_integrity_verify_fn(struct work_struct *work)
{
        struct bio_integrity_payload *bip =
                container_of(work, struct bio_integrity_payload, bip_work);
        struct bio *bio = bip->bip_bio;
        struct blk_integrity *bi = bdev_get_integrity(bio->bi_bdev);

        bio->bi_error = bio_integrity_process(bio, bi->profile->verify_fn);

        /* Restore original bio completion handler */
        bio->bi_end_io = bip->bip_end_io;
        bio_endio(bio);
}

/**
 * bio_integrity_endio - Integrity I/O completion function
 * @bio:        Protected bio
 * @error:      Pointer to errno
 *
 * Description: Completion for integrity I/O
 *
 * Normally I/O completion is done in interrupt context.  However,
 * verifying I/O integrity is a time-consuming task which must be run
 * in process context.  This function postpones completion
 * accordingly.
 */
void bio_integrity_endio(struct bio *bio)
{
        struct bio_integrity_payload *bip = bio_integrity(bio);

        BUG_ON(bip->bip_bio != bio);

        /* In case of an I/O error there is no point in verifying the
         * integrity metadata.  Restore original bio end_io handler
         * and run it.
         */
        if (bio->bi_error) {
                bio->bi_end_io = bip->bip_end_io;
                bio_endio(bio);

                return;
        }

        INIT_WORK(&bip->bip_work, bio_integrity_verify_fn);
        queue_work(kintegrityd_wq, &bip->bip_work);
}
EXPORT_SYMBOL(bio_integrity_endio);

/**
 * bio_integrity_advance - Advance integrity vector
 * @bio:        bio whose integrity vector to update
 * @bytes_done: number of data bytes that have been completed
 *
 * Description: This function calculates how many integrity bytes the
 * number of completed data bytes correspond to and advances the
 * integrity vector accordingly.
 */
void bio_integrity_advance(struct bio *bio, unsigned int bytes_done)
{
        struct bio_integrity_payload *bip = bio_integrity(bio);
        struct blk_integrity *bi = bdev_get_integrity(bio->bi_bdev);
        unsigned bytes = bio_integrity_bytes(bi, bytes_done >> 9);

        bvec_iter_advance(bip->bip_vec, &bip->bip_iter, bytes);
}
EXPORT_SYMBOL(bio_integrity_advance);

/**
 * bio_integrity_trim - Trim integrity vector
 * @bio:        bio whose integrity vector to update
 * @offset:     offset to first data sector
 * @sectors:    number of data sectors
 *
 * Description: Used to trim the integrity vector in a cloned bio.
 * The ivec will be advanced corresponding to 'offset' data sectors
 * and the length will be truncated corresponding to 'len' data
 * sectors.
 */
void bio_integrity_trim(struct bio *bio, unsigned int offset,
                        unsigned int sectors)
{
        struct bio_integrity_payload *bip = bio_integrity(bio);
        struct blk_integrity *bi = bdev_get_integrity(bio->bi_bdev);

        bio_integrity_advance(bio, offset << 9);
        bip->bip_iter.bi_size = bio_integrity_bytes(bi, sectors);
}
EXPORT_SYMBOL(bio_integrity_trim);

/**
 * bio_integrity_clone - Callback for cloning bios with integrity metadata
 * @bio:        New bio
 * @bio_src:    Original bio
 * @gfp_mask:   Memory allocation mask
 *
 * Description: Called to allocate a bip when cloning a bio
 */
int bio_integrity_clone(struct bio *bio, struct bio *bio_src,
                        gfp_t gfp_mask)
{
        struct bio_integrity_payload *bip_src = bio_integrity(bio_src);
        struct bio_integrity_payload *bip;

        BUG_ON(bip_src == NULL);

        bip = bio_integrity_alloc(bio, gfp_mask, bip_src->bip_vcnt);
        if (IS_ERR(bip))
                return PTR_ERR(bip);

        memcpy(bip->bip_vec, bip_src->bip_vec,
               bip_src->bip_vcnt * sizeof(struct bio_vec));

        bip->bip_vcnt = bip_src->bip_vcnt;
        bip->bip_iter = bip_src->bip_iter;

        return 0;
}
EXPORT_SYMBOL(bio_integrity_clone);

int bioset_integrity_create(struct bio_set *bs, int pool_size)
{
        if (bs->bio_integrity_pool)
                return 0;

        bs->bio_integrity_pool = mempool_create_slab_pool(pool_size, bip_slab);
        if (!bs->bio_integrity_pool)
                return -1;

        bs->bvec_integrity_pool = biovec_create_pool(pool_size);
        if (!bs->bvec_integrity_pool) {
                mempool_destroy(bs->bio_integrity_pool);
                return -1;
        }

        return 0;
}
EXPORT_SYMBOL(bioset_integrity_create);

void bioset_integrity_free(struct bio_set *bs)
{
        if (bs->bio_integrity_pool)
                mempool_destroy(bs->bio_integrity_pool);

        if (bs->bvec_integrity_pool)
                mempool_destroy(bs->bvec_integrity_pool);
}
EXPORT_SYMBOL(bioset_integrity_free);

void __init bio_integrity_init(void)
{
        /*
         * kintegrityd won't block much but may burn a lot of CPU cycles.
         * Make it highpri CPU intensive wq with max concurrency of 1.
         */
        kintegrityd_wq = alloc_workqueue("kintegrityd", WQ_MEM_RECLAIM |
                                         WQ_HIGHPRI | WQ_CPU_INTENSIVE, 1);
        if (!kintegrityd_wq)
                panic("Failed to create kintegrityd\n");

        bip_slab = kmem_cache_create("bio_integrity_payload",
                                     sizeof(struct bio_integrity_payload) +
                                     sizeof(struct bio_vec) * BIP_INLINE_VECS,
                                     0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
}