/*
   * 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>
  
  #define BIP_INLINE_VECS	4
  
  static struct kmem_cache *bip_slab;
  static struct workqueue_struct *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 long idx = BIO_POOL_NONE;
  	unsigned inline_vecs;
  
  	if (!bs) {
  		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 NULL;
  
  	memset(bip, 0, sizeof(*bip));
  
  	if (nr_vecs > inline_vecs) {
  		bip->bip_vec = bvec_alloc(gfp_mask, nr_vecs, &idx,
  					  bs->bvec_integrity_pool);
  		if (!bip->bip_vec)
  			goto err;
  	} else {
  		bip->bip_vec = bip->bip_inline_vecs;
  	}
  
  	bip->bip_slab = idx;
  	bip->bip_bio = bio;
  	bio->bi_integrity = bip;
  
  	return bip;
  err:
  	mempool_free(bip, bs->bio_integrity_pool);
  	return NULL;
  }
  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->bi_integrity;
  	struct bio_set *bs = bio->bi_pool;
  
  	if (bip->bip_owns_buf)
  		kfree(bip->bip_buf);
  
  	if (bs) {
  		if (bip->bip_slab != BIO_POOL_NONE)
  			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);
  
  static inline unsigned int bip_integrity_vecs(struct bio_integrity_payload *bip)
  {
  	if (bip->bip_slab == BIO_POOL_NONE)
  		return BIP_INLINE_VECS;
  
  	return bvec_nr_vecs(bip->bip_slab);
  }
  
  /**
   * 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->bi_integrity;
  	struct bio_vec *iv;
  
  	if (bip->bip_vcnt >= bip_integrity_vecs(bip)) {
  		printk(KERN_ERR "%s: bip_vec full
  ", __func__);
  		return 0;
  	}
  
  	iv = bip->bip_vec + bip->bip_vcnt;
  
  	iv->bv_page = page;
  	iv->bv_len = len;
  	iv->bv_offset = offset;
  	bip->bip_vcnt++;
  
  	return len;
  }
  EXPORT_SYMBOL(bio_integrity_add_page);
  
  static int bdev_integrity_enabled(struct block_device *bdev, int rw)
  {
  	struct blk_integrity *bi = bdev_get_integrity(bdev);
  
  	if (bi == NULL)
  		return 0;
  
  	if (rw == READ && bi->verify_fn != NULL &&
  	    (bi->flags & INTEGRITY_FLAG_READ))
  		return 1;
  
  	if (rw == WRITE && bi->generate_fn != NULL &&
  	    (bi->flags & INTEGRITY_FLAG_WRITE))
  		return 1;
  
  	return 0;
  }
  
  /**
   * 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.
   */
  int bio_integrity_enabled(struct bio *bio)
  {
  	/* Already protected? */
  	if (bio_integrity(bio))
  		return 0;
  
  	return bdev_integrity_enabled(bio->bi_bdev, bio_data_dir(bio));
  }
  EXPORT_SYMBOL(bio_integrity_enabled);
  
  /**
   * bio_integrity_hw_sectors - Convert 512b sectors to hardware ditto
   * @bi:		blk_integrity profile for device
   * @sectors:	Number of 512 sectors to convert
   *
   * Description: The block layer calculates everything in 512 byte
   * sectors but integrity metadata is done in terms of the hardware
   * sector size of the storage device.  Convert the block layer sectors
   * to physical sectors.
   */
  static inline unsigned int bio_integrity_hw_sectors(struct blk_integrity *bi,
  						    unsigned int sectors)
  {
  	/* At this point there are only 512b or 4096b DIF/EPP devices */
  	if (bi->sector_size == 4096)
  		return sectors >>= 3;
  
  	return sectors;
  }
  
  static inline unsigned int bio_integrity_bytes(struct blk_integrity *bi,
  					       unsigned int sectors)
  {
  	return bio_integrity_hw_sectors(bi, sectors) * bi->tuple_size;
  }
  
  /**
   * bio_integrity_tag_size - Retrieve integrity tag space
   * @bio:	bio to inspect
   *
   * Description: Returns the maximum number of tag bytes that can be
   * attached to this bio. Filesystems can use this to determine how
   * much metadata to attach to an I/O.
   */
  unsigned int bio_integrity_tag_size(struct bio *bio)
  {
  	struct blk_integrity *bi = bdev_get_integrity(bio->bi_bdev);
  
  	BUG_ON(bio->bi_iter.bi_size == 0);
  
  	return bi->tag_size * (bio->bi_iter.bi_size / bi->sector_size);
  }
  EXPORT_SYMBOL(bio_integrity_tag_size);
  
  static int bio_integrity_tag(struct bio *bio, void *tag_buf, unsigned int len,
  			     int set)
  {
  	struct bio_integrity_payload *bip = bio->bi_integrity;
  	struct blk_integrity *bi = bdev_get_integrity(bio->bi_bdev);
  	unsigned int nr_sectors;
  
  	BUG_ON(bip->bip_buf == NULL);
  
  	if (bi->tag_size == 0)
  		return -1;
  
  	nr_sectors = bio_integrity_hw_sectors(bi,
  					DIV_ROUND_UP(len, bi->tag_size));
  
  	if (nr_sectors * bi->tuple_size > bip->bip_iter.bi_size) {
  		printk(KERN_ERR "%s: tag too big for bio: %u > %u
  ", __func__,
  		       nr_sectors * bi->tuple_size, bip->bip_iter.bi_size);
  		return -1;
  	}
  
  	if (set)
  		bi->set_tag_fn(bip->bip_buf, tag_buf, nr_sectors);
  	else
  		bi->get_tag_fn(bip->bip_buf, tag_buf, nr_sectors);
  
  	return 0;
  }
  
  /**
   * bio_integrity_set_tag - Attach a tag buffer to a bio
   * @bio:	bio to attach buffer to
   * @tag_buf:	Pointer to a buffer containing tag data
   * @len:	Length of the included buffer
   *
   * Description: Use this function to tag a bio by leveraging the extra
   * space provided by devices formatted with integrity protection.  The
   * size of the integrity buffer must be <= to the size reported by
   * bio_integrity_tag_size().
   */
  int bio_integrity_set_tag(struct bio *bio, void *tag_buf, unsigned int len)
  {
  	BUG_ON(bio_data_dir(bio) != WRITE);
  
  	return bio_integrity_tag(bio, tag_buf, len, 1);
  }
  EXPORT_SYMBOL(bio_integrity_set_tag);
  
  /**
   * bio_integrity_get_tag - Retrieve a tag buffer from a bio
   * @bio:	bio to retrieve buffer from
   * @tag_buf:	Pointer to a buffer for the tag data
   * @len:	Length of the target buffer
   *
   * Description: Use this function to retrieve the tag buffer from a
   * completed I/O. The size of the integrity buffer must be <= to the
   * size reported by bio_integrity_tag_size().
   */
  int bio_integrity_get_tag(struct bio *bio, void *tag_buf, unsigned int len)
  {
  	BUG_ON(bio_data_dir(bio) != READ);
  
  	return bio_integrity_tag(bio, tag_buf, len, 0);
  }
  EXPORT_SYMBOL(bio_integrity_get_tag);
  
  /**
   * bio_integrity_generate - Generate integrity metadata for a bio
   * @bio:	bio to generate integrity metadata for
   *
   * Description: Generates integrity metadata for a bio by calling the
   * block device's generation callback function.  The bio must have a
   * bip attached with enough room to accommodate the generated
   * integrity metadata.
   */
  static void bio_integrity_generate(struct bio *bio)
  {
  	struct blk_integrity *bi = bdev_get_integrity(bio->bi_bdev);
  	struct blk_integrity_exchg bix;
  	struct bio_vec bv;
  	struct bvec_iter iter;
  	sector_t sector = bio->bi_iter.bi_sector;
  	unsigned int sectors, total;
  	void *prot_buf = bio->bi_integrity->bip_buf;
  
  	total = 0;
  	bix.disk_name = bio->bi_bdev->bd_disk->disk_name;
  	bix.sector_size = bi->sector_size;
  
  	bio_for_each_segment(bv, bio, iter) {
  		void *kaddr = kmap_atomic(bv.bv_page);
  		bix.data_buf = kaddr + bv.bv_offset;
  		bix.data_size = bv.bv_len;
  		bix.prot_buf = prot_buf;
  		bix.sector = sector;
  
  		bi->generate_fn(&bix);
  
  		sectors = bv.bv_len / bi->sector_size;
  		sector += sectors;
  		prot_buf += sectors * bi->tuple_size;
  		total += sectors * bi->tuple_size;
  		BUG_ON(total > bio->bi_integrity->bip_iter.bi_size);
  
  		kunmap_atomic(kaddr);
  	}
  }
  
  static inline unsigned short blk_integrity_tuple_size(struct blk_integrity *bi)
  {
  	if (bi)
  		return bi->tuple_size;
  
  	return 0;
  }
  
  /**
   * 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 sectors;
  
  	bi = bdev_get_integrity(bio->bi_bdev);
  	q = bdev_get_queue(bio->bi_bdev);
  	BUG_ON(bi == NULL);
  	BUG_ON(bio_integrity(bio));
  
  	sectors = bio_integrity_hw_sectors(bi, bio_sectors(bio));
  
  	/* Allocate kernel buffer for protection data */
  	len = sectors * blk_integrity_tuple_size(bi);
  	buf = kmalloc(len, GFP_NOIO | q->bounce_gfp);
  	if (unlikely(buf == NULL)) {
  		printk(KERN_ERR "could not allocate integrity buffer
  ");
  		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 (unlikely(bip == NULL)) {
  		printk(KERN_ERR "could not allocate data integrity bioset
  ");
  		kfree(buf);
  		return -EIO;
  	}
  
  	bip->bip_owns_buf = 1;
  	bip->bip_buf = buf;
  	bip->bip_iter.bi_size = len;
  	bip->bip_iter.bi_sector = bio->bi_iter.bi_sector;
  
  	/* 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_generate(bio);
  
  	return 0;
  }
  EXPORT_SYMBOL(bio_integrity_prep);
  
  /**
   * bio_integrity_verify - Verify integrity metadata for a bio
   * @bio:	bio to verify
   *
   * Description: This function is called to verify the integrity of a
   * bio.	 The data in the bio io_vec is compared to the integrity
   * metadata returned by the HBA.
   */
  static int bio_integrity_verify(struct bio *bio)
  {
  	struct blk_integrity *bi = bdev_get_integrity(bio->bi_bdev);
  	struct blk_integrity_exchg bix;
  	struct bio_vec *bv;
  	sector_t sector = bio->bi_integrity->bip_iter.bi_sector;
  	unsigned int sectors, ret = 0;
  	void *prot_buf = bio->bi_integrity->bip_buf;
  	int i;
  
  	bix.disk_name = bio->bi_bdev->bd_disk->disk_name;
  	bix.sector_size = bi->sector_size;
  
  	bio_for_each_segment_all(bv, bio, i) {
  		void *kaddr = kmap_atomic(bv->bv_page);
  
  		bix.data_buf = kaddr + bv->bv_offset;
  		bix.data_size = bv->bv_len;
  		bix.prot_buf = prot_buf;
  		bix.sector = sector;
  
  		ret = bi->verify_fn(&bix);
  
  		if (ret) {
  			kunmap_atomic(kaddr);
  			return ret;
  		}
  
  		sectors = bv->bv_len / bi->sector_size;
  		sector += sectors;
  		prot_buf += sectors * bi->tuple_size;
  
  		kunmap_atomic(kaddr);
  	}
  
  	return ret;
  }
  
  /**
   * 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;
  	int error;
  
  	error = bio_integrity_verify(bio);
  
  	/* Restore original bio completion handler */
  	bio->bi_end_io = bip->bip_end_io;
  	bio_endio_nodec(bio, error);
  }
  
  /**
   * 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, int error)
  {
  	struct bio_integrity_payload *bip = bio->bi_integrity;
  
  	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 (error) {
  		bio->bi_end_io = bip->bip_end_io;
  		bio_endio(bio, error);
  
  		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->bi_integrity;
  	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->bi_integrity;
  	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_src->bi_integrity;
  	struct bio_integrity_payload *bip;
  
  	BUG_ON(bip_src == NULL);
  
  	bip = bio_integrity_alloc(bio, gfp_mask, bip_src->bip_vcnt);
  
  	if (bip == NULL)
  		return -EIO;
  
  	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(bs, 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
  ");
  
  	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);
  	if (!bip_slab)
  		panic("Failed to create slab
  ");
  }