/*
 * Copyright (C) 2003 Christophe Saout <christophe@saout.de>
 * Copyright (C) 2004 Clemens Fruhwirth <clemens@endorphin.org>
 * Copyright (C) 2006-2008 Red Hat, Inc. All rights reserved.
 *
 * This file is released under the GPL.
 */

#include <linux/completion.h>
#include <linux/err.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/mempool.h>
#include <linux/slab.h>
#include <linux/crypto.h>
#include <linux/workqueue.h>
#include <linux/backing-dev.h>
#include <asm/atomic.h>
#include <linux/scatterlist.h>
#include <asm/page.h>
#include <asm/unaligned.h>

#include <linux/device-mapper.h>

#define DM_MSG_PREFIX "crypt"
#define MESG_STR(x) x, sizeof(x)

/*
 * context holding the current state of a multi-part conversion
 */
struct convert_context {
        struct completion restart;
        struct bio *bio_in;
        struct bio *bio_out;
        unsigned int offset_in;
        unsigned int offset_out;
        unsigned int idx_in;
        unsigned int idx_out;
        sector_t sector;
        atomic_t pending;
};

/*
 * per bio private data
 */
struct dm_crypt_io {
        struct dm_target *target;
        struct bio *base_bio;
        struct work_struct work;

        struct convert_context ctx;

        atomic_t pending;
        int error;
        sector_t sector;
        struct dm_crypt_io *base_io;
};

struct dm_crypt_request {
        struct convert_context *ctx;
        struct scatterlist sg_in;
        struct scatterlist sg_out;
};

struct crypt_config;

struct crypt_iv_operations {
        int (*ctr)(struct crypt_config *cc, struct dm_target *ti,
                   const char *opts);
        void (*dtr)(struct crypt_config *cc);
        const char *(*status)(struct crypt_config *cc);
        int (*generator)(struct crypt_config *cc, u8 *iv, sector_t sector);
};

/*
 * Crypt: maps a linear range of a block device
 * and encrypts / decrypts at the same time.
 */
enum flags { DM_CRYPT_SUSPENDED, DM_CRYPT_KEY_VALID };
struct crypt_config {
        struct dm_dev *dev;
        sector_t start;

        /*
         * pool for per bio private data, crypto requests and
         * encryption requeusts/buffer pages
         */
        mempool_t *io_pool;
        mempool_t *req_pool;
        mempool_t *page_pool;
        struct bio_set *bs;

        struct workqueue_struct *io_queue;
        struct workqueue_struct *crypt_queue;

        /*
         * crypto related data
         */
        struct crypt_iv_operations *iv_gen_ops;
        char *iv_mode;
        union {
                struct crypto_cipher *essiv_tfm;
                int benbi_shift;
        } iv_gen_private;
        sector_t iv_offset;
        unsigned int iv_size;

        /*
         * Layout of each crypto request:
         *
         *   struct ablkcipher_request
         *      context
         *      padding
         *   struct dm_crypt_request
         *      padding
         *   IV
         *
         * The padding is added so that dm_crypt_request and the IV are
         * correctly aligned.
         */
        unsigned int dmreq_start;
        struct ablkcipher_request *req;

        char cipher[CRYPTO_MAX_ALG_NAME];
        char chainmode[CRYPTO_MAX_ALG_NAME];
        struct crypto_ablkcipher *tfm;
        unsigned long flags;
        unsigned int key_size;
        u8 key[0];
};

#define MIN_IOS        16
#define MIN_POOL_PAGES 32
#define MIN_BIO_PAGES  8

static struct kmem_cache *_crypt_io_pool;

static void clone_init(struct dm_crypt_io *, struct bio *);
static void kcryptd_queue_crypt(struct dm_crypt_io *io);

/*
 * Different IV generation algorithms:
 *
 * plain: the initial vector is the 32-bit little-endian version of the sector
 *        number, padded with zeros if necessary.
 *
 * essiv: "encrypted sector|salt initial vector", the sector number is
 *        encrypted with the bulk cipher using a salt as key. The salt
 *        should be derived from the bulk cipher's key via hashing.
 *
 * benbi: the 64-bit "big-endian 'narrow block'-count", starting at 1
 *        (needed for LRW-32-AES and possible other narrow block modes)
 *
 * null: the initial vector is always zero.  Provides compatibility with
 *       obsolete loop_fish2 devices.  Do not use for new devices.
 *
 * plumb: unimplemented, see:
 * http://article.gmane.org/gmane.linux.kernel.device-mapper.dm-crypt/454
 */

static int crypt_iv_plain_gen(struct crypt_config *cc, u8 *iv, sector_t sector)
{
        memset(iv, 0, cc->iv_size);
        *(u32 *)iv = cpu_to_le32(sector & 0xffffffff);

        return 0;
}

static int crypt_iv_essiv_ctr(struct crypt_config *cc, struct dm_target *ti,
                              const char *opts)
{
        struct crypto_cipher *essiv_tfm;
        struct crypto_hash *hash_tfm;
        struct hash_desc desc;
        struct scatterlist sg;
        unsigned int saltsize;
        u8 *salt;
        int err;

        if (opts == NULL) {
                ti->error = "Digest algorithm missing for ESSIV mode";
                return -EINVAL;
        }

        /* Hash the cipher key with the given hash algorithm */
        hash_tfm = crypto_alloc_hash(opts, 0, CRYPTO_ALG_ASYNC);
        if (IS_ERR(hash_tfm)) {
                ti->error = "Error initializing ESSIV hash";
                return PTR_ERR(hash_tfm);
        }

        saltsize = crypto_hash_digestsize(hash_tfm);
        salt = kmalloc(saltsize, GFP_KERNEL);
        if (salt == NULL) {
                ti->error = "Error kmallocing salt storage in ESSIV";
                crypto_free_hash(hash_tfm);
                return -ENOMEM;
        }

        sg_init_one(&sg, cc->key, cc->key_size);
        desc.tfm = hash_tfm;
        desc.flags = CRYPTO_TFM_REQ_MAY_SLEEP;
        err = crypto_hash_digest(&desc, &sg, cc->key_size, salt);
        crypto_free_hash(hash_tfm);

        if (err) {
                ti->error = "Error calculating hash in ESSIV";
                kfree(salt);
                return err;
        }

        /* Setup the essiv_tfm with the given salt */
        essiv_tfm = crypto_alloc_cipher(cc->cipher, 0, CRYPTO_ALG_ASYNC);
        if (IS_ERR(essiv_tfm)) {
                ti->error = "Error allocating crypto tfm for ESSIV";
                kfree(salt);
                return PTR_ERR(essiv_tfm);
        }
        if (crypto_cipher_blocksize(essiv_tfm) !=
            crypto_ablkcipher_ivsize(cc->tfm)) {
                ti->error = "Block size of ESSIV cipher does "
                            "not match IV size of block cipher";
                crypto_free_cipher(essiv_tfm);
                kfree(salt);
                return -EINVAL;
        }
        err = crypto_cipher_setkey(essiv_tfm, salt, saltsize);
        if (err) {
                ti->error = "Failed to set key for ESSIV cipher";
                crypto_free_cipher(essiv_tfm);
                kfree(salt);
                return err;
        }
        kfree(salt);

        cc->iv_gen_private.essiv_tfm = essiv_tfm;
        return 0;
}

static void crypt_iv_essiv_dtr(struct crypt_config *cc)
{
        crypto_free_cipher(cc->iv_gen_private.essiv_tfm);
        cc->iv_gen_private.essiv_tfm = NULL;
}

static int crypt_iv_essiv_gen(struct crypt_config *cc, u8 *iv, sector_t sector)
{
        memset(iv, 0, cc->iv_size);
        *(u64 *)iv = cpu_to_le64(sector);
        crypto_cipher_encrypt_one(cc->iv_gen_private.essiv_tfm, iv, iv);
        return 0;
}

static int crypt_iv_benbi_ctr(struct crypt_config *cc, struct dm_target *ti,
                              const char *opts)
{
        unsigned bs = crypto_ablkcipher_blocksize(cc->tfm);
        int log = ilog2(bs);

        /* we need to calculate how far we must shift the sector count
         * to get the cipher block count, we use this shift in _gen */

        if (1 << log != bs) {
                ti->error = "cypher blocksize is not a power of 2";
                return -EINVAL;
        }

        if (log > 9) {
                ti->error = "cypher blocksize is > 512";
                return -EINVAL;
        }

        cc->iv_gen_private.benbi_shift = 9 - log;

        return 0;
}

static void crypt_iv_benbi_dtr(struct crypt_config *cc)
{
}

static int crypt_iv_benbi_gen(struct crypt_config *cc, u8 *iv, sector_t sector)
{
        __be64 val;

        memset(iv, 0, cc->iv_size - sizeof(u64)); /* rest is cleared below */

        val = cpu_to_be64(((u64)sector << cc->iv_gen_private.benbi_shift) + 1);
        put_unaligned(val, (__be64 *)(iv + cc->iv_size - sizeof(u64)));

        return 0;
}

static int crypt_iv_null_gen(struct crypt_config *cc, u8 *iv, sector_t sector)
{
        memset(iv, 0, cc->iv_size);

        return 0;
}

static struct crypt_iv_operations crypt_iv_plain_ops = {
        .generator = crypt_iv_plain_gen
};

static struct crypt_iv_operations crypt_iv_essiv_ops = {
        .ctr       = crypt_iv_essiv_ctr,
        .dtr       = crypt_iv_essiv_dtr,
        .generator = crypt_iv_essiv_gen
};

static struct crypt_iv_operations crypt_iv_benbi_ops = {
        .ctr       = crypt_iv_benbi_ctr,
        .dtr       = crypt_iv_benbi_dtr,
        .generator = crypt_iv_benbi_gen
};

static struct crypt_iv_operations crypt_iv_null_ops = {
        .generator = crypt_iv_null_gen
};

static void crypt_convert_init(struct crypt_config *cc,
                               struct convert_context *ctx,
                               struct bio *bio_out, struct bio *bio_in,
                               sector_t sector)
{
        ctx->bio_in = bio_in;
        ctx->bio_out = bio_out;
        ctx->offset_in = 0;
        ctx->offset_out = 0;
        ctx->idx_in = bio_in ? bio_in->bi_idx : 0;
        ctx->idx_out = bio_out ? bio_out->bi_idx : 0;
        ctx->sector = sector + cc->iv_offset;
        init_completion(&ctx->restart);
}

static struct dm_crypt_request *dmreq_of_req(struct crypt_config *cc,
                                             struct ablkcipher_request *req)
{
        return (struct dm_crypt_request *)((char *)req + cc->dmreq_start);
}

static struct ablkcipher_request *req_of_dmreq(struct crypt_config *cc,
                                               struct dm_crypt_request *dmreq)
{
        return (struct ablkcipher_request *)((char *)dmreq - cc->dmreq_start);
}

static int crypt_convert_block(struct crypt_config *cc,
                               struct convert_context *ctx,
                               struct ablkcipher_request *req)
{
        struct bio_vec *bv_in = bio_iovec_idx(ctx->bio_in, ctx->idx_in);
        struct bio_vec *bv_out = bio_iovec_idx(ctx->bio_out, ctx->idx_out);
        struct dm_crypt_request *dmreq;
        u8 *iv;
        int r = 0;

        dmreq = dmreq_of_req(cc, req);
        iv = (u8 *)ALIGN((unsigned long)(dmreq + 1),
                         crypto_ablkcipher_alignmask(cc->tfm) + 1);

        dmreq->ctx = ctx;
        sg_init_table(&dmreq->sg_in, 1);
        sg_set_page(&dmreq->sg_in, bv_in->bv_page, 1 << SECTOR_SHIFT,
                    bv_in->bv_offset + ctx->offset_in);

        sg_init_table(&dmreq->sg_out, 1);
        sg_set_page(&dmreq->sg_out, bv_out->bv_page, 1 << SECTOR_SHIFT,
                    bv_out->bv_offset + ctx->offset_out);

        ctx->offset_in += 1 << SECTOR_SHIFT;
        if (ctx->offset_in >= bv_in->bv_len) {
                ctx->offset_in = 0;
                ctx->idx_in++;
        }

        ctx->offset_out += 1 << SECTOR_SHIFT;
        if (ctx->offset_out >= bv_out->bv_len) {
                ctx->offset_out = 0;
                ctx->idx_out++;
        }

        if (cc->iv_gen_ops) {
                r = cc->iv_gen_ops->generator(cc, iv, ctx->sector);
                if (r < 0)
                        return r;
        }

        ablkcipher_request_set_crypt(req, &dmreq->sg_in, &dmreq->sg_out,
                                     1 << SECTOR_SHIFT, iv);

        if (bio_data_dir(ctx->bio_in) == WRITE)
                r = crypto_ablkcipher_encrypt(req);
        else
                r = crypto_ablkcipher_decrypt(req);

        return r;
}

static void kcryptd_async_done(struct crypto_async_request *async_req,
                               int error);
static void crypt_alloc_req(struct crypt_config *cc,
                            struct convert_context *ctx)
{
        if (!cc->req)
                cc->req = mempool_alloc(cc->req_pool, GFP_NOIO);
        ablkcipher_request_set_tfm(cc->req, cc->tfm);
        ablkcipher_request_set_callback(cc->req, CRYPTO_TFM_REQ_MAY_BACKLOG |
                                        CRYPTO_TFM_REQ_MAY_SLEEP,
                                        kcryptd_async_done,
                                        dmreq_of_req(cc, cc->req));
}

/*
 * Encrypt / decrypt data from one bio to another one (can be the same one)
 */
static int crypt_convert(struct crypt_config *cc,
                         struct convert_context *ctx)
{
        int r;

        atomic_set(&ctx->pending, 1);

        while(ctx->idx_in < ctx->bio_in->bi_vcnt &&
              ctx->idx_out < ctx->bio_out->bi_vcnt) {

                crypt_alloc_req(cc, ctx);

                atomic_inc(&ctx->pending);

                r = crypt_convert_block(cc, ctx, cc->req);

                switch (r) {
                /* async */
                case -EBUSY:
                        wait_for_completion(&ctx->restart);
                        INIT_COMPLETION(ctx->restart);
                        /* fall through*/
                case -EINPROGRESS:
                        cc->req = NULL;
                        ctx->sector++;
                        continue;

                /* sync */
                case 0:
                        atomic_dec(&ctx->pending);
                        ctx->sector++;
                        cond_resched();
                        continue;

                /* error */
                default:
                        atomic_dec(&ctx->pending);
                        return r;
                }
        }

        return 0;
}

static void dm_crypt_bio_destructor(struct bio *bio)
{
        struct dm_crypt_io *io = bio->bi_private;
        struct crypt_config *cc = io->target->private;

        bio_free(bio, cc->bs);
}

/*
 * Generate a new unfragmented bio with the given size
 * This should never violate the device limitations
 * May return a smaller bio when running out of pages, indicated by
 * *out_of_pages set to 1.
 */
static struct bio *crypt_alloc_buffer(struct dm_crypt_io *io, unsigned size,
                                      unsigned *out_of_pages)
{
        struct crypt_config *cc = io->target->private;
        struct bio *clone;
        unsigned int nr_iovecs = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
        gfp_t gfp_mask = GFP_NOIO | __GFP_HIGHMEM;
        unsigned i, len;
        struct page *page;

        clone = bio_alloc_bioset(GFP_NOIO, nr_iovecs, cc->bs);
        if (!clone)
                return NULL;

        clone_init(io, clone);
        *out_of_pages = 0;

        for (i = 0; i < nr_iovecs; i++) {
                page = mempool_alloc(cc->page_pool, gfp_mask);
                if (!page) {
                        *out_of_pages = 1;
                        break;
                }

                /*
                 * if additional pages cannot be allocated without waiting,
                 * return a partially allocated bio, the caller will then try
                 * to allocate additional bios while submitting this partial bio
                 */
                if (i == (MIN_BIO_PAGES - 1))
                        gfp_mask = (gfp_mask | __GFP_NOWARN) & ~__GFP_WAIT;

                len = (size > PAGE_SIZE) ? PAGE_SIZE : size;

                if (!bio_add_page(clone, page, len, 0)) {
                        mempool_free(page, cc->page_pool);
                        break;
                }

                size -= len;
        }

        if (!clone->bi_size) {
                bio_put(clone);
                return NULL;
        }

        return clone;
}

static void crypt_free_buffer_pages(struct crypt_config *cc, struct bio *clone)
{
        unsigned int i;
        struct bio_vec *bv;

        for (i = 0; i < clone->bi_vcnt; i++) {
                bv = bio_iovec_idx(clone, i);
                BUG_ON(!bv->bv_page);
                mempool_free(bv->bv_page, cc->page_pool);
                bv->bv_page = NULL;
        }
}

static struct dm_crypt_io *crypt_io_alloc(struct dm_target *ti,
                                          struct bio *bio, sector_t sector)
{
        struct crypt_config *cc = ti->private;
        struct dm_crypt_io *io;

        io = mempool_alloc(cc->io_pool, GFP_NOIO);
        io->target = ti;
        io->base_bio = bio;
        io->sector = sector;
        io->error = 0;
        io->base_io = NULL;
        atomic_set(&io->pending, 0);

        return io;
}

static void crypt_inc_pending(struct dm_crypt_io *io)
{
        atomic_inc(&io->pending);
}

/*
 * One of the bios was finished. Check for completion of
 * the whole request and correctly clean up the buffer.
 * If base_io is set, wait for the last fragment to complete.
 */
static void crypt_dec_pending(struct dm_crypt_io *io)
{
        struct crypt_config *cc = io->target->private;
        struct bio *base_bio = io->base_bio;
        struct dm_crypt_io *base_io = io->base_io;
        int error = io->error;

        if (!atomic_dec_and_test(&io->pending))
                return;

        mempool_free(io, cc->io_pool);

        if (likely(!base_io))
                bio_endio(base_bio, error);
        else {
                if (error && !base_io->error)
                        base_io->error = error;
                crypt_dec_pending(base_io);
        }
}

/*
 * kcryptd/kcryptd_io:
 *
 * Needed because it would be very unwise to do decryption in an
 * interrupt context.
 *
 * kcryptd performs the actual encryption or decryption.
 *
 * kcryptd_io performs the IO submission.
 *
 * They must be separated as otherwise the final stages could be
 * starved by new requests which can block in the first stages due
 * to memory allocation.
 */
static void crypt_endio(struct bio *clone, int error)
{
        struct dm_crypt_io *io = clone->bi_private;
        struct crypt_config *cc = io->target->private;
        unsigned rw = bio_data_dir(clone);

        if (unlikely(!bio_flagged(clone, BIO_UPTODATE) && !error))
                error = -EIO;

        /*
         * free the processed pages
         */
        if (rw == WRITE)
                crypt_free_buffer_pages(cc, clone);

        bio_put(clone);

        if (rw == READ && !error) {
                kcryptd_queue_crypt(io);
                return;
        }

        if (unlikely(error))
                io->error = error;

        crypt_dec_pending(io);
}

static void clone_init(struct dm_crypt_io *io, struct bio *clone)
{
        struct crypt_config *cc = io->target->private;

        clone->bi_private = io;
        clone->bi_end_io  = crypt_endio;
        clone->bi_bdev    = cc->dev->bdev;
        clone->bi_rw      = io->base_bio->bi_rw;
        clone->bi_destructor = dm_crypt_bio_destructor;
}

static void kcryptd_io_read(struct dm_crypt_io *io)
{
        struct crypt_config *cc = io->target->private;
        struct bio *base_bio = io->base_bio;
        struct bio *clone;

        crypt_inc_pending(io);

        /*
         * The block layer might modify the bvec array, so always
         * copy the required bvecs because we need the original
         * one in order to decrypt the whole bio data *afterwards*.
         */
        clone = bio_alloc_bioset(GFP_NOIO, bio_segments(base_bio), cc->bs);
        if (unlikely(!clone)) {
                io->error = -ENOMEM;
                crypt_dec_pending(io);
                return;
        }

        clone_init(io, clone);
        clone->bi_idx = 0;
        clone->bi_vcnt = bio_segments(base_bio);
        clone->bi_size = base_bio->bi_size;
        clone->bi_sector = cc->start + io->sector;
        memcpy(clone->bi_io_vec, bio_iovec(base_bio),
               sizeof(struct bio_vec) * clone->bi_vcnt);

        generic_make_request(clone);
}

static void kcryptd_io_write(struct dm_crypt_io *io)
{
        struct bio *clone = io->ctx.bio_out;
        generic_make_request(clone);
}

static void kcryptd_io(struct work_struct *work)
{
        struct dm_crypt_io *io = container_of(work, struct dm_crypt_io, work);

        if (bio_data_dir(io->base_bio) == READ)
                kcryptd_io_read(io);
        else
                kcryptd_io_write(io);
}

static void kcryptd_queue_io(struct dm_crypt_io *io)
{
        struct crypt_config *cc = io->target->private;

        INIT_WORK(&io->work, kcryptd_io);
        queue_work(cc->io_queue, &io->work);
}

static void kcryptd_crypt_write_io_submit(struct dm_crypt_io *io,
                                          int error, int async)
{
        struct bio *clone = io->ctx.bio_out;
        struct crypt_config *cc = io->target->private;

        if (unlikely(error < 0)) {
                crypt_free_buffer_pages(cc, clone);
                bio_put(clone);
                io->error = -EIO;
                crypt_dec_pending(io);
                return;
        }

        /* crypt_convert should have filled the clone bio */
        BUG_ON(io->ctx.idx_out < clone->bi_vcnt);

        clone->bi_sector = cc->start + io->sector;

        if (async)
                kcryptd_queue_io(io);
        else
                generic_make_request(clone);
}

static void kcryptd_crypt_write_convert(struct dm_crypt_io *io)
{
        struct crypt_config *cc = io->target->private;
        struct bio *clone;
        struct dm_crypt_io *new_io;
        int crypt_finished;
        unsigned out_of_pages = 0;
        unsigned remaining = io->base_bio->bi_size;
        sector_t sector = io->sector;
        int r;

        /*
         * Prevent io from disappearing until this function completes.
         */
        crypt_inc_pending(io);
        crypt_convert_init(cc, &io->ctx, NULL, io->base_bio, sector);

        /*
         * The allocated buffers can be smaller than the whole bio,
         * so repeat the whole process until all the data can be handled.
         */
        while (remaining) {
                clone = crypt_alloc_buffer(io, remaining, &out_of_pages);
                if (unlikely(!clone)) {
                        io->error = -ENOMEM;
                        break;
                }

                io->ctx.bio_out = clone;
                io->ctx.idx_out = 0;

                remaining -= clone->bi_size;
                sector += bio_sectors(clone);

                crypt_inc_pending(io);
                r = crypt_convert(cc, &io->ctx);
                crypt_finished = atomic_dec_and_test(&io->ctx.pending);

                /* Encryption was already finished, submit io now */
                if (crypt_finished) {
                        kcryptd_crypt_write_io_submit(io, r, 0);

                        /*
                         * If there was an error, do not try next fragments.
                         * For async, error is processed in async handler.
                         */
                        if (unlikely(r < 0))
                                break;

                        io->sector = sector;
                }

                /*
                 * Out of memory -> run queues
                 * But don't wait if split was due to the io size restriction
                 */
                if (unlikely(out_of_pages))
                        congestion_wait(BLK_RW_ASYNC, HZ/100);

                /*
                 * With async crypto it is unsafe to share the crypto context
                 * between fragments, so switch to a new dm_crypt_io structure.
                 */
                if (unlikely(!crypt_finished && remaining)) {
                        new_io = crypt_io_alloc(io->target, io->base_bio,
                                                sector);
                        crypt_inc_pending(new_io);
                        crypt_convert_init(cc, &new_io->ctx, NULL,
                                           io->base_bio, sector);
                        new_io->ctx.idx_in = io->ctx.idx_in;
                        new_io->ctx.offset_in = io->ctx.offset_in;

                        /*
                         * Fragments after the first use the base_io
                         * pending count.
                         */
                        if (!io->base_io)
                                new_io->base_io = io;
                        else {
                                new_io->base_io = io->base_io;
                                crypt_inc_pending(io->base_io);
                                crypt_dec_pending(io);
                        }

                        io = new_io;
                }
        }

        crypt_dec_pending(io);
}

static void kcryptd_crypt_read_done(struct dm_crypt_io *io, int error)
{
        if (unlikely(error < 0))
                io->error = -EIO;

        crypt_dec_pending(io);
}

static void kcryptd_crypt_read_convert(struct dm_crypt_io *io)
{
        struct crypt_config *cc = io->target->private;
        int r = 0;

        crypt_inc_pending(io);

        crypt_convert_init(cc, &io->ctx, io->base_bio, io->base_bio,
                           io->sector);

        r = crypt_convert(cc, &io->ctx);

        if (atomic_dec_and_test(&io->ctx.pending))
                kcryptd_crypt_read_done(io, r);

        crypt_dec_pending(io);
}

static void kcryptd_async_done(struct crypto_async_request *async_req,
                               int error)
{
        struct dm_crypt_request *dmreq = async_req->data;
        struct convert_context *ctx = dmreq->ctx;
        struct dm_crypt_io *io = container_of(ctx, struct dm_crypt_io, ctx);
        struct crypt_config *cc = io->target->private;

        if (error == -EINPROGRESS) {
                complete(&ctx->restart);
                return;
        }

        mempool_free(req_of_dmreq(cc, dmreq), cc->req_pool);

        if (!atomic_dec_and_test(&ctx->pending))
                return;

        if (bio_data_dir(io->base_bio) == READ)
                kcryptd_crypt_read_done(io, error);
        else
                kcryptd_crypt_write_io_submit(io, error, 1);
}

static void kcryptd_crypt(struct work_struct *work)
{
        struct dm_crypt_io *io = container_of(work, struct dm_crypt_io, work);

        if (bio_data_dir(io->base_bio) == READ)
                kcryptd_crypt_read_convert(io);
        else
                kcryptd_crypt_write_convert(io);
}

static void kcryptd_queue_crypt(struct dm_crypt_io *io)
{
        struct crypt_config *cc = io->target->private;

        INIT_WORK(&io->work, kcryptd_crypt);
        queue_work(cc->crypt_queue, &io->work);
}

/*
 * Decode key from its hex representation
 */
static int crypt_decode_key(u8 *key, char *hex, unsigned int size)
{
        char buffer[3];
        char *endp;
        unsigned int i;

        buffer[2] = '\0';

        for (i = 0; i < size; i++) {
                buffer[0] = *hex++;
                buffer[1] = *hex++;

                key[i] = (u8)simple_strtoul(buffer, &endp, 16);

                if (endp != &buffer[2])
                        return -EINVAL;
        }

        if (*hex != '\0')
                return -EINVAL;

        return 0;
}

/*
 * Encode key into its hex representation
 */
static void crypt_encode_key(char *hex, u8 *key, unsigned int size)
{
        unsigned int i;

        for (i = 0; i < size; i++) {
                sprintf(hex, "%02x", *key);
                hex += 2;
                key++;
        }
}

static int crypt_set_key(struct crypt_config *cc, char *key)
{
        unsigned key_size = strlen(key) >> 1;

        if (cc->key_size && cc->key_size != key_size)
                return -EINVAL;

        cc->key_size = key_size; /* initial settings */

        if ((!key_size && strcmp(key, "-")) ||
           (key_size && crypt_decode_key(cc->key, key, key_size) < 0))
                return -EINVAL;

        set_bit(DM_CRYPT_KEY_VALID, &cc->flags);

        return 0;
}

static int crypt_wipe_key(struct crypt_config *cc)
{
        clear_bit(DM_CRYPT_KEY_VALID, &cc->flags);
        memset(&cc->key, 0, cc->key_size * sizeof(u8));
        return 0;
}

/*
 * Construct an encryption mapping:
 * <cipher> <key> <iv_offset> <dev_path> <start>
 */
static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
{
        struct crypt_config *cc;
        struct crypto_ablkcipher *tfm;
        char *tmp;
        char *cipher;
        char *chainmode;
        char *ivmode;
        char *ivopts;
        unsigned int key_size;
        unsigned long long tmpll;

        if (argc != 5) {
                ti->error = "Not enough arguments";
                return -EINVAL;
        }

        tmp = argv[0];
        cipher = strsep(&tmp, "-");
        chainmode = strsep(&tmp, "-");
        ivopts = strsep(&tmp, "-");
        ivmode = strsep(&ivopts, ":");

        if (tmp)
                DMWARN("Unexpected additional cipher options");

        key_size = strlen(argv[1]) >> 1;

        cc = kzalloc(sizeof(*cc) + key_size * sizeof(u8), GFP_KERNEL);
        if (cc == NULL) {
                ti->error =
                        "Cannot allocate transparent encryption context";
                return -ENOMEM;
        }

        if (crypt_set_key(cc, argv[1])) {
                ti->error = "Error decoding key";
                goto bad_cipher;
        }

        /* Compatiblity mode for old dm-crypt cipher strings */
        if (!chainmode || (strcmp(chainmode, "plain") == 0 && !ivmode)) {
                chainmode = "cbc";
                ivmode = "plain";
        }

        if (strcmp(chainmode, "ecb") && !ivmode) {
                ti->error = "This chaining mode requires an IV mechanism";
                goto bad_cipher;
        }

        if (snprintf(cc->cipher, CRYPTO_MAX_ALG_NAME, "%s(%s)",
                     chainmode, cipher) >= CRYPTO_MAX_ALG_NAME) {
                ti->error = "Chain mode + cipher name is too long";
                goto bad_cipher;
        }

        tfm = crypto_alloc_ablkcipher(cc->cipher, 0, 0);
        if (IS_ERR(tfm)) {
                ti->error = "Error allocating crypto tfm";
                goto bad_cipher;
        }

        strcpy(cc->cipher, cipher);
        strcpy(cc->chainmode, chainmode);
        cc->tfm = tfm;

        /*
         * Choose ivmode. Valid modes: "plain", "essiv:<esshash>", "benbi".
         * See comments at iv code
         */

        if (ivmode == NULL)
                cc->iv_gen_ops = NULL;
        else if (strcmp(ivmode, "plain") == 0)
                cc->iv_gen_ops = &crypt_iv_plain_ops;
        else if (strcmp(ivmode, "essiv") == 0)
                cc->iv_gen_ops = &crypt_iv_essiv_ops;
        else if (strcmp(ivmode, "benbi") == 0)
                cc->iv_gen_ops = &crypt_iv_benbi_ops;
        else if (strcmp(ivmode, "null") == 0)
                cc->iv_gen_ops = &crypt_iv_null_ops;
        else {
                ti->error = "Invalid IV mode";
                goto bad_ivmode;
        }

        if (cc->iv_gen_ops && cc->iv_gen_ops->ctr &&
            cc->iv_gen_ops->ctr(cc, ti, ivopts) < 0)
                goto bad_ivmode;

        cc->iv_size = crypto_ablkcipher_ivsize(tfm);
        if (cc->iv_size)
                /* at least a 64 bit sector number should fit in our buffer */
                cc->iv_size = max(cc->iv_size,
                                  (unsigned int)(sizeof(u64) / sizeof(u8)));
        else {
                if (cc->iv_gen_ops) {
                        DMWARN("Selected cipher does not support IVs");
                        if (cc->iv_gen_ops->dtr)
                                cc->iv_gen_ops->dtr(cc);
                        cc->iv_gen_ops = NULL;
                }
        }

        cc->io_pool = mempool_create_slab_pool(MIN_IOS, _crypt_io_pool);
        if (!cc->io_pool) {
                ti->error = "Cannot allocate crypt io mempool";
                goto bad_slab_pool;
        }

        cc->dmreq_start = sizeof(struct ablkcipher_request);
        cc->dmreq_start += crypto_ablkcipher_reqsize(tfm);
        cc->dmreq_start = ALIGN(cc->dmreq_start, crypto_tfm_ctx_alignment());
        cc->dmreq_start += crypto_ablkcipher_alignmask(tfm) &
                           ~(crypto_tfm_ctx_alignment() - 1);

        cc->req_pool = mempool_create_kmalloc_pool(MIN_IOS, cc->dmreq_start +
                        sizeof(struct dm_crypt_request) + cc->iv_size);
        if (!cc->req_pool) {
                ti->error = "Cannot allocate crypt request mempool";
                goto bad_req_pool;
        }
        cc->req = NULL;

        cc->page_pool = mempool_create_page_pool(MIN_POOL_PAGES, 0);
        if (!cc->page_pool) {
                ti->error = "Cannot allocate page mempool";
                goto bad_page_pool;
        }

        cc->bs = bioset_create(MIN_IOS, 0);
        if (!cc->bs) {
                ti->error = "Cannot allocate crypt bioset";
                goto bad_bs;
        }

        if (crypto_ablkcipher_setkey(tfm, cc->key, key_size) < 0) {
                ti->error = "Error setting key";
                goto bad_device;
        }

        if (sscanf(argv[2], "%llu", &tmpll) != 1) {
                ti->error = "Invalid iv_offset sector";
                goto bad_device;
        }
        cc->iv_offset = tmpll;

        if (sscanf(argv[4], "%llu", &tmpll) != 1) {
                ti->error = "Invalid device sector";
                goto bad_device;
        }
        cc->start = tmpll;

        if (dm_get_device(ti, argv[3], cc->start, ti->len,
                          dm_table_get_mode(ti->table), &cc->dev)) {
                ti->error = "Device lookup failed";
                goto bad_device;
        }

        if (ivmode && cc->iv_gen_ops) {
                if (ivopts)
                        *(ivopts - 1) = ':';
                cc->iv_mode = kmalloc(strlen(ivmode) + 1, GFP_KERNEL);
                if (!cc->iv_mode) {
                        ti->error = "Error kmallocing iv_mode string";
                        goto bad_ivmode_string;
                }
                strcpy(cc->iv_mode, ivmode);
        } else
                cc->iv_mode = NULL;

        cc->io_queue = create_singlethread_workqueue("kcryptd_io");
        if (!cc->io_queue) {
                ti->error = "Couldn't create kcryptd io queue";
                goto bad_io_queue;
        }

        cc->crypt_queue = create_singlethread_workqueue("kcryptd");
        if (!cc->crypt_queue) {
                ti->error = "Couldn't create kcryptd queue";
                goto bad_crypt_queue;
        }

        ti->num_flush_requests = 1;
        ti->private = cc;
        return 0;

bad_crypt_queue:
        destroy_workqueue(cc->io_queue);
bad_io_queue:
        kfree(cc->iv_mode);
bad_ivmode_string:
        dm_put_device(ti, cc->dev);
bad_device:
        bioset_free(cc->bs);
bad_bs:
        mempool_destroy(cc->page_pool);
bad_page_pool:
        mempool_destroy(cc->req_pool);
bad_req_pool:
        mempool_destroy(cc->io_pool);
bad_slab_pool:
        if (cc->iv_gen_ops && cc->iv_gen_ops->dtr)
                cc->iv_gen_ops->dtr(cc);
bad_ivmode:
        crypto_free_ablkcipher(tfm);
bad_cipher:
        /* Must zero key material before freeing */
        kzfree(cc);
        return -EINVAL;
}

static void crypt_dtr(struct dm_target *ti)
{
        struct crypt_config *cc = (struct crypt_config *) ti->private;

        destroy_workqueue(cc->io_queue);
        destroy_workqueue(cc->crypt_queue);

        if (cc->req)
                mempool_free(cc->req, cc->req_pool);

        bioset_free(cc->bs);
        mempool_destroy(cc->page_pool);
        mempool_destroy(cc->req_pool);
        mempool_destroy(cc->io_pool);

        kfree(cc->iv_mode);
        if (cc->iv_gen_ops && cc->iv_gen_ops->dtr)
                cc->iv_gen_ops->dtr(cc);
        crypto_free_ablkcipher(cc->tfm);
        dm_put_device(ti, cc->dev);

        /* Must zero key material before freeing */
        kzfree(cc);
}

static int crypt_map(struct dm_target *ti, struct bio *bio,
                     union map_info *map_context)
{
        struct dm_crypt_io *io;
        struct crypt_config *cc;

        if (unlikely(bio_empty_barrier(bio))) {
                cc = ti->private;
                bio->bi_bdev = cc->dev->bdev;
                return DM_MAPIO_REMAPPED;
        }

        io = crypt_io_alloc(ti, bio, bio->bi_sector - ti->begin);

        if (bio_data_dir(io->base_bio) == READ)
                kcryptd_queue_io(io);
        else
                kcryptd_queue_crypt(io);

        return DM_MAPIO_SUBMITTED;
}

static int crypt_status(struct dm_target *ti, status_type_t type,
                        char *result, unsigned int maxlen)
{
        struct crypt_config *cc = (struct crypt_config *) ti->private;
        unsigned int sz = 0;

        switch (type) {
        case STATUSTYPE_INFO:
                result[0] = '\0';
                break;

        case STATUSTYPE_TABLE:
                if (cc->iv_mode)
                        DMEMIT("%s-%s-%s ", cc->cipher, cc->chainmode,
                               cc->iv_mode);
                else
                        DMEMIT("%s-%s ", cc->cipher, cc->chainmode);

                if (cc->key_size > 0) {
                        if ((maxlen - sz) < ((cc->key_size << 1) + 1))
                                return -ENOMEM;

                        crypt_encode_key(result + sz, cc->key, cc->key_size);
                        sz += cc->key_size << 1;
                } else {
                        if (sz >= maxlen)
                                return -ENOMEM;
                        result[sz++] = '-';
                }

                DMEMIT(" %llu %s %llu", (unsigned long long)cc->iv_offset,
                                cc->dev->name, (unsigned long long)cc->start);
                break;
        }
        return 0;
}

static void crypt_postsuspend(struct dm_target *ti)
{
        struct crypt_config *cc = ti->private;

        set_bit(DM_CRYPT_SUSPENDED, &cc->flags);
}

static int crypt_preresume(struct dm_target *ti)
{
        struct crypt_config *cc = ti->private;

        if (!test_bit(DM_CRYPT_KEY_VALID, &cc->flags)) {
                DMERR("aborting resume - crypt key is not set.");
                return -EAGAIN;
        }

        return 0;
}

static void crypt_resume(struct dm_target *ti)
{
        struct crypt_config *cc = ti->private;

        clear_bit(DM_CRYPT_SUSPENDED, &cc->flags);
}

/* Message interface
 *      key set <key>
 *      key wipe
 */
static int crypt_message(struct dm_target *ti, unsigned argc, char **argv)
{
        struct crypt_config *cc = ti->private;

        if (argc < 2)
                goto error;

        if (!strnicmp(argv[0], MESG_STR("key"))) {
                if (!test_bit(DM_CRYPT_SUSPENDED, &cc->flags)) {
                        DMWARN("not suspended during key manipulation.");
                        return -EINVAL;
                }
                if (argc == 3 && !strnicmp(argv[1], MESG_STR("set")))
                        return crypt_set_key(cc, argv[2]);
                if (argc == 2 && !strnicmp(argv[1], MESG_STR("wipe")))
                        return crypt_wipe_key(cc);
        }

error:
        DMWARN("unrecognised message received.");
        return -EINVAL;
}

static int crypt_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
                       struct bio_vec *biovec, int max_size)
{
        struct crypt_config *cc = ti->private;
        struct request_queue *q = bdev_get_queue(cc->dev->bdev);

        if (!q->merge_bvec_fn)
                return max_size;

        bvm->bi_bdev = cc->dev->bdev;
        bvm->bi_sector = cc->start + bvm->bi_sector - ti->begin;

        return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
}

static int crypt_iterate_devices(struct dm_target *ti,
                                 iterate_devices_callout_fn fn, void *data)
{
        struct crypt_config *cc = ti->private;

        return fn(ti, cc->dev, cc->start, ti->len, data);
}

static struct target_type crypt_target = {
        .name   = "crypt",
        .version = {1, 7, 0},
        .module = THIS_MODULE,
        .ctr    = crypt_ctr,
        .dtr    = crypt_dtr,
        .map    = crypt_map,
        .status = crypt_status,
        .postsuspend = crypt_postsuspend,
        .preresume = crypt_preresume,
        .resume = crypt_resume,
        .message = crypt_message,
        .merge  = crypt_merge,
        .iterate_devices = crypt_iterate_devices,
};

static int __init dm_crypt_init(void)
{
        int r;

        _crypt_io_pool = KMEM_CACHE(dm_crypt_io, 0);
        if (!_crypt_io_pool)
                return -ENOMEM;

        r = dm_register_target(&crypt_target);
        if (r < 0) {
                DMERR("register failed %d", r);
                kmem_cache_destroy(_crypt_io_pool);
        }

        return r;
}

static void __exit dm_crypt_exit(void)
{
        dm_unregister_target(&crypt_target);
        kmem_cache_destroy(_crypt_io_pool);
}

module_init(dm_crypt_init);
module_exit(dm_crypt_exit);

MODULE_AUTHOR("Christophe Saout <christophe@saout.de>");
MODULE_DESCRIPTION(DM_NAME " target for transparent encryption / decryption");
MODULE_LICENSE("GPL");