fs/iomap/bio.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2010 Red Hat, Inc.
 * Copyright (C) 2016-2023 Christoph Hellwig.
 */
#include <linux/iomap.h>
#include <linux/pagemap.h>
#include "internal.h"
#include "trace.h"

static void iomap_read_end_io(struct bio *bio)
{
	int error = blk_status_to_errno(bio->bi_status);
	struct folio_iter fi;

	bio_for_each_folio_all(fi, bio)
		iomap_finish_folio_read(fi.folio, fi.offset, fi.length, error);
	bio_put(bio);
}

static void iomap_bio_submit_read(struct iomap_read_folio_ctx *ctx)
{
	struct bio *bio = ctx->read_ctx;

	if (bio)
		submit_bio(bio);
}

static int iomap_bio_read_folio_range(const struct iomap_iter *iter,
		struct iomap_read_folio_ctx *ctx, size_t plen)
{
	struct folio *folio = ctx->cur_folio;
	const struct iomap *iomap = &iter->iomap;
	loff_t pos = iter->pos;
	size_t poff = offset_in_folio(folio, pos);
	loff_t length = iomap_length(iter);
	sector_t sector;
	struct bio *bio = ctx->read_ctx;

	sector = iomap_sector(iomap, pos);
	if (!bio || bio_end_sector(bio) != sector ||
	    !bio_add_folio(bio, folio, plen, poff)) {
		gfp_t gfp = mapping_gfp_constraint(folio->mapping, GFP_KERNEL);
		gfp_t orig_gfp = gfp;
		unsigned int nr_vecs = DIV_ROUND_UP(length, PAGE_SIZE);

		if (bio)
			submit_bio(bio);

		if (ctx->rac) /* same as readahead_gfp_mask */
			gfp |= __GFP_NORETRY | __GFP_NOWARN;
		bio = bio_alloc(iomap->bdev, bio_max_segs(nr_vecs), REQ_OP_READ,
				     gfp);
		/*
		 * If the bio_alloc fails, try it again for a single page to
		 * avoid having to deal with partial page reads.  This emulates
		 * what do_mpage_read_folio does.
		 */
		if (!bio)
			bio = bio_alloc(iomap->bdev, 1, REQ_OP_READ, orig_gfp);
		if (ctx->rac)
			bio->bi_opf |= REQ_RAHEAD;
		bio->bi_iter.bi_sector = sector;
		bio->bi_end_io = iomap_read_end_io;
		bio_add_folio_nofail(bio, folio, plen, poff);
		ctx->read_ctx = bio;
	}
	return 0;
}

const struct iomap_read_ops iomap_bio_read_ops = {
	.read_folio_range = iomap_bio_read_folio_range,
	.submit_read = iomap_bio_submit_read,
};
EXPORT_SYMBOL_GPL(iomap_bio_read_ops);

int iomap_bio_read_folio_range_sync(const struct iomap_iter *iter,
		struct folio *folio, loff_t pos, size_t len)
{
	const struct iomap *srcmap = iomap_iter_srcmap(iter);
	struct bio_vec bvec;
	struct bio bio;

	bio_init(&bio, srcmap->bdev, &bvec, 1, REQ_OP_READ);
	bio.bi_iter.bi_sector = iomap_sector(srcmap, pos);
	bio_add_folio_nofail(&bio, folio, len, offset_in_folio(folio, pos));
	return submit_bio_wait(&bio);
}