text: // SPDX-License-Identifier: GPL-2.0
  /*
   * Functions related to generic helpers functions
   */
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/bio.h>
  #include <linux/blkdev.h>
  #include <linux/scatterlist.h>
  
  #include "blk.h"
  
  static struct bio *next_bio(struct bio *bio, unsigned int nr_pages,
  		gfp_t gfp)
  {
  	struct bio *new = bio_alloc(gfp, nr_pages);
  
  	if (bio) {
  		bio_chain(bio, new);
  		submit_bio(bio);
  	}
  
  	return new;
  }
  
  int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,
  		sector_t nr_sects, gfp_t gfp_mask, int flags,
  		struct bio **biop)
  {
  	struct request_queue *q = bdev_get_queue(bdev);
  	struct bio *bio = *biop;
  	unsigned int granularity;
  	unsigned int op;
  	int alignment;
  	sector_t bs_mask;
  
  	if (!q)
  		return -ENXIO;
  
  	if (bdev_read_only(bdev))
  		return -EPERM;
  
  	if (flags & BLKDEV_DISCARD_SECURE) {
  		if (!blk_queue_secure_erase(q))
  			return -EOPNOTSUPP;
  		op = REQ_OP_SECURE_ERASE;
  	} else {
  		if (!blk_queue_discard(q))
  			return -EOPNOTSUPP;
  		op = REQ_OP_DISCARD;
  	}
  
  	bs_mask = (bdev_logical_block_size(bdev) >> 9) - 1;
  	if ((sector | nr_sects) & bs_mask)
  		return -EINVAL;
  
  	/* Zero-sector (unknown) and one-sector granularities are the same.  */
  	granularity = max(q->limits.discard_granularity >> 9, 1U);
  	alignment = (bdev_discard_alignment(bdev) >> 9) % granularity;
  
  	while (nr_sects) {
  		unsigned int req_sects;
  		sector_t end_sect, tmp;
  
  		/*
  		 * Issue in chunks of the user defined max discard setting,
  		 * ensuring that bi_size doesn't overflow
  		 */
  		req_sects = min_t(sector_t, nr_sects,
  					q->limits.max_discard_sectors);
  		if (!req_sects)
  			goto fail;
  		if (req_sects > UINT_MAX >> 9)
  			req_sects = UINT_MAX >> 9;
  
  		/*
  		 * If splitting a request, and the next starting sector would be
  		 * misaligned, stop the discard at the previous aligned sector.
  		 */
  		end_sect = sector + req_sects;
  		tmp = end_sect;
  		if (req_sects < nr_sects &&
  		    sector_div(tmp, granularity) != alignment) {
  			end_sect = end_sect - alignment;
  			sector_div(end_sect, granularity);
  			end_sect = end_sect * granularity + alignment;
  			req_sects = end_sect - sector;
  		}
  
  		bio = next_bio(bio, 0, gfp_mask);
  		bio->bi_iter.bi_sector = sector;
  		bio_set_dev(bio, bdev);
  		bio_set_op_attrs(bio, op, 0);
  
  		bio->bi_iter.bi_size = req_sects << 9;
  		nr_sects -= req_sects;
  		sector = end_sect;
  
  		/*
  		 * We can loop for a long time in here, if someone does
  		 * full device discards (like mkfs). Be nice and allow
  		 * us to schedule out to avoid softlocking if preempt
  		 * is disabled.
  		 */
  		cond_resched();
  	}
  
  	*biop = bio;
  	return 0;
  
  fail:
  	if (bio) {
  		submit_bio_wait(bio);
  		bio_put(bio);
  	}
  	*biop = NULL;
  	return -EOPNOTSUPP;
  }
  EXPORT_SYMBOL(__blkdev_issue_discard);
  
  /**
   * blkdev_issue_discard - queue a discard
   * @bdev:	blockdev to issue discard for
   * @sector:	start sector
   * @nr_sects:	number of sectors to discard
   * @gfp_mask:	memory allocation flags (for bio_alloc)
   * @flags:	BLKDEV_DISCARD_* flags to control behaviour
   *
   * Description:
   *    Issue a discard request for the sectors in question.
   */
  int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
  		sector_t nr_sects, gfp_t gfp_mask, unsigned long flags)
  {
  	struct bio *bio = NULL;
  	struct blk_plug plug;
  	int ret;
  
  	blk_start_plug(&plug);
  	ret = __blkdev_issue_discard(bdev, sector, nr_sects, gfp_mask, flags,
  			&bio);
  	if (!ret && bio) {
  		ret = submit_bio_wait(bio);
  		if (ret == -EOPNOTSUPP)
  			ret = 0;
  		bio_put(bio);
  	}
  	blk_finish_plug(&plug);
  
  	return ret;
  }
  EXPORT_SYMBOL(blkdev_issue_discard);
  
  /**
   * __blkdev_issue_write_same - generate number of bios with same page
   * @bdev:	target blockdev
   * @sector:	start sector
   * @nr_sects:	number of sectors to write
   * @gfp_mask:	memory allocation flags (for bio_alloc)
   * @page:	page containing data to write
   * @biop:	pointer to anchor bio
   *
   * Description:
   *  Generate and issue number of bios(REQ_OP_WRITE_SAME) with same page.
   */
  static int __blkdev_issue_write_same(struct block_device *bdev, sector_t sector,
  		sector_t nr_sects, gfp_t gfp_mask, struct page *page,
  		struct bio **biop)
  {
  	struct request_queue *q = bdev_get_queue(bdev);
  	unsigned int max_write_same_sectors;
  	struct bio *bio = *biop;
  	sector_t bs_mask;
  
  	if (!q)
  		return -ENXIO;
  
  	if (bdev_read_only(bdev))
  		return -EPERM;
  
  	bs_mask = (bdev_logical_block_size(bdev) >> 9) - 1;
  	if ((sector | nr_sects) & bs_mask)
  		return -EINVAL;
  
  	if (!bdev_write_same(bdev))
  		return -EOPNOTSUPP;
  
  	/* Ensure that max_write_same_sectors doesn't overflow bi_size */
  	max_write_same_sectors = UINT_MAX >> 9;
  
  	while (nr_sects) {
  		bio = next_bio(bio, 1, gfp_mask);
  		bio->bi_iter.bi_sector = sector;
  		bio_set_dev(bio, bdev);
  		bio->bi_vcnt = 1;
  		bio->bi_io_vec->bv_page = page;
  		bio->bi_io_vec->bv_offset = 0;
  		bio->bi_io_vec->bv_len = bdev_logical_block_size(bdev);
  		bio_set_op_attrs(bio, REQ_OP_WRITE_SAME, 0);
  
  		if (nr_sects > max_write_same_sectors) {
  			bio->bi_iter.bi_size = max_write_same_sectors << 9;
  			nr_sects -= max_write_same_sectors;
  			sector += max_write_same_sectors;
  		} else {
  			bio->bi_iter.bi_size = nr_sects << 9;
  			nr_sects = 0;
  		}
  		cond_resched();
  	}
  
  	*biop = bio;
  	return 0;
  }
  
  /**
   * blkdev_issue_write_same - queue a write same operation
   * @bdev:	target blockdev
   * @sector:	start sector
   * @nr_sects:	number of sectors to write
   * @gfp_mask:	memory allocation flags (for bio_alloc)
   * @page:	page containing data
   *
   * Description:
   *    Issue a write same request for the sectors in question.
   */
  int blkdev_issue_write_same(struct block_device *bdev, sector_t sector,
  				sector_t nr_sects, gfp_t gfp_mask,
  				struct page *page)
  {
  	struct bio *bio = NULL;
  	struct blk_plug plug;
  	int ret;
  
  	blk_start_plug(&plug);
  	ret = __blkdev_issue_write_same(bdev, sector, nr_sects, gfp_mask, page,
  			&bio);
  	if (ret == 0 && bio) {
  		ret = submit_bio_wait(bio);
  		bio_put(bio);
  	}
  	blk_finish_plug(&plug);
  	return ret;
  }
  EXPORT_SYMBOL(blkdev_issue_write_same);
  
  static int __blkdev_issue_write_zeroes(struct block_device *bdev,
  		sector_t sector, sector_t nr_sects, gfp_t gfp_mask,
  		struct bio **biop, unsigned flags)
  {
  	struct bio *bio = *biop;
  	unsigned int max_write_zeroes_sectors;
  	struct request_queue *q = bdev_get_queue(bdev);
  
  	if (!q)
  		return -ENXIO;
  
  	if (bdev_read_only(bdev))
  		return -EPERM;
  
  	/* Ensure that max_write_zeroes_sectors doesn't overflow bi_size */
  	max_write_zeroes_sectors = bdev_write_zeroes_sectors(bdev);
  
  	if (max_write_zeroes_sectors == 0)
  		return -EOPNOTSUPP;
  
  	while (nr_sects) {
  		bio = next_bio(bio, 0, gfp_mask);
  		bio->bi_iter.bi_sector = sector;
  		bio_set_dev(bio, bdev);
  		bio->bi_opf = REQ_OP_WRITE_ZEROES;
  		if (flags & BLKDEV_ZERO_NOUNMAP)
  			bio->bi_opf |= REQ_NOUNMAP;
  
  		if (nr_sects > max_write_zeroes_sectors) {
  			bio->bi_iter.bi_size = max_write_zeroes_sectors << 9;
  			nr_sects -= max_write_zeroes_sectors;
  			sector += max_write_zeroes_sectors;
  		} else {
  			bio->bi_iter.bi_size = nr_sects << 9;
  			nr_sects = 0;
  		}
  		cond_resched();
  	}
  
  	*biop = bio;
  	return 0;
  }
  
  /*
   * Convert a number of 512B sectors to a number of pages.
   * The result is limited to a number of pages that can fit into a BIO.
   * Also make sure that the result is always at least 1 (page) for the cases
   * where nr_sects is lower than the number of sectors in a page.
   */
  static unsigned int __blkdev_sectors_to_bio_pages(sector_t nr_sects)
  {
  	sector_t pages = DIV_ROUND_UP_SECTOR_T(nr_sects, PAGE_SIZE / 512);
  
  	return min(pages, (sector_t)BIO_MAX_PAGES);
  }
  
  static int __blkdev_issue_zero_pages(struct block_device *bdev,
  		sector_t sector, sector_t nr_sects, gfp_t gfp_mask,
  		struct bio **biop)
  {
  	struct request_queue *q = bdev_get_queue(bdev);
  	struct bio *bio = *biop;
  	int bi_size = 0;
  	unsigned int sz;
  
  	if (!q)
  		return -ENXIO;
  
  	if (bdev_read_only(bdev))
  		return -EPERM;
  
  	while (nr_sects != 0) {
  		bio = next_bio(bio, __blkdev_sectors_to_bio_pages(nr_sects),
  			       gfp_mask);
  		bio->bi_iter.bi_sector = sector;
  		bio_set_dev(bio, bdev);
  		bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
  
  		while (nr_sects != 0) {
  			sz = min((sector_t) PAGE_SIZE, nr_sects << 9);
  			bi_size = bio_add_page(bio, ZERO_PAGE(0), sz, 0);
  			nr_sects -= bi_size >> 9;
  			sector += bi_size >> 9;
  			if (bi_size < sz)
  				break;
  		}
  		cond_resched();
  	}
  
  	*biop = bio;
  	return 0;
  }
  
  /**
   * __blkdev_issue_zeroout - generate number of zero filed write bios
   * @bdev:	blockdev to issue
   * @sector:	start sector
   * @nr_sects:	number of sectors to write
   * @gfp_mask:	memory allocation flags (for bio_alloc)
   * @biop:	pointer to anchor bio
   * @flags:	controls detailed behavior
   *
   * Description:
   *  Zero-fill a block range, either using hardware offload or by explicitly
   *  writing zeroes to the device.
   *
   *  If a device is using logical block provisioning, the underlying space will
   *  not be released if %flags contains BLKDEV_ZERO_NOUNMAP.
   *
   *  If %flags contains BLKDEV_ZERO_NOFALLBACK, the function will return
   *  -EOPNOTSUPP if no explicit hardware offload for zeroing is provided.
   */
  int __blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
  		sector_t nr_sects, gfp_t gfp_mask, struct bio **biop,
  		unsigned flags)
  {
  	int ret;
  	sector_t bs_mask;
  
  	bs_mask = (bdev_logical_block_size(bdev) >> 9) - 1;
  	if ((sector | nr_sects) & bs_mask)
  		return -EINVAL;
  
  	ret = __blkdev_issue_write_zeroes(bdev, sector, nr_sects, gfp_mask,
  			biop, flags);
  	if (ret != -EOPNOTSUPP || (flags & BLKDEV_ZERO_NOFALLBACK))
  		return ret;
  
  	return __blkdev_issue_zero_pages(bdev, sector, nr_sects, gfp_mask,
  					 biop);
  }
  EXPORT_SYMBOL(__blkdev_issue_zeroout);
  
  /**
   * blkdev_issue_zeroout - zero-fill a block range
   * @bdev:	blockdev to write
   * @sector:	start sector
   * @nr_sects:	number of sectors to write
   * @gfp_mask:	memory allocation flags (for bio_alloc)
   * @flags:	controls detailed behavior
   *
   * Description:
   *  Zero-fill a block range, either using hardware offload or by explicitly
   *  writing zeroes to the device.  See __blkdev_issue_zeroout() for the
   *  valid values for %flags.
   */
  int blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
  		sector_t nr_sects, gfp_t gfp_mask, unsigned flags)
  {
  	int ret = 0;
  	sector_t bs_mask;
  	struct bio *bio;
  	struct blk_plug plug;
  	bool try_write_zeroes = !!bdev_write_zeroes_sectors(bdev);
  
  	bs_mask = (bdev_logical_block_size(bdev) >> 9) - 1;
  	if ((sector | nr_sects) & bs_mask)
  		return -EINVAL;
  
  retry:
  	bio = NULL;
  	blk_start_plug(&plug);
  	if (try_write_zeroes) {
  		ret = __blkdev_issue_write_zeroes(bdev, sector, nr_sects,
  						  gfp_mask, &bio, flags);
  	} else if (!(flags & BLKDEV_ZERO_NOFALLBACK)) {
  		ret = __blkdev_issue_zero_pages(bdev, sector, nr_sects,
  						gfp_mask, &bio);
  	} else {
  		/* No zeroing offload support */
  		ret = -EOPNOTSUPP;
  	}
  	if (ret == 0 && bio) {
  		ret = submit_bio_wait(bio);
  		bio_put(bio);
  	}
  	blk_finish_plug(&plug);
  	if (ret && try_write_zeroes) {
  		if (!(flags & BLKDEV_ZERO_NOFALLBACK)) {
  			try_write_zeroes = false;
  			goto retry;
  		}
  		if (!bdev_write_zeroes_sectors(bdev)) {
  			/*
  			 * Zeroing offload support was indicated, but the
  			 * device reported ILLEGAL REQUEST (for some devices
  			 * there is no non-destructive way to verify whether
  			 * WRITE ZEROES is actually supported).
  			 */
  			ret = -EOPNOTSUPP;
  		}
  	}
  
  	return ret;
  }
  EXPORT_SYMBOL(blkdev_issue_zeroout);
  