blk-lib.c

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/*
 * 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"

struct bio_batch {
    atomic_t        done;
    unsigned long       flags;
    struct completion   *wait;
};

static void bio_batch_end_io(struct bio *bio, int err)
{
    struct bio_batch *bb = bio->bi_private;

    if (err && (err != -EOPNOTSUPP))
        clear_bit(BIO_UPTODATE, &bb->flags);
    if (atomic_dec_and_test(&bb->done))
        complete(bb->wait);
    bio_put(bio);
}

int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
        sector_t nr_sects, gfp_t gfp_mask, unsigned long flags)
{
    DECLARE_COMPLETION_ONSTACK(wait);
    struct request_queue *q = bdev_get_queue(bdev);
    int type = REQ_WRITE | REQ_DISCARD;
    unsigned int max_discard_sectors;
    unsigned int granularity, alignment, mask;
    struct bio_batch bb;
    struct bio *bio;
    int ret = 0;

    if (!q)
        return -ENXIO;

    if (!blk_queue_discard(q))
        return -EOPNOTSUPP;

    /* Zero-sector (unknown) and one-sector granularities are the same.  */
    granularity = max(q->limits.discard_granularity >> 9, 1U);
    mask = granularity - 1;
    alignment = (bdev_discard_alignment(bdev) >> 9) & mask;

    /*
     * Ensure that max_discard_sectors is of the proper
     * granularity, so that requests stay aligned after a split.
     */
    max_discard_sectors = min(q->limits.max_discard_sectors, UINT_MAX >> 9);
    max_discard_sectors = round_down(max_discard_sectors, granularity);
    if (unlikely(!max_discard_sectors)) {
        /* Avoid infinite loop below. Being cautious never hurts. */
        return -EOPNOTSUPP;
    }

    if (flags & BLKDEV_DISCARD_SECURE) {
        if (!blk_queue_secdiscard(q))
            return -EOPNOTSUPP;
        type |= REQ_SECURE;
    }

    atomic_set(&bb.done, 1);
    bb.flags = 1 << BIO_UPTODATE;
    bb.wait = &wait;

    while (nr_sects) {
        unsigned int req_sects;
        sector_t end_sect;

        bio = bio_alloc(gfp_mask, 1);
        if (!bio) {
            ret = -ENOMEM;
            break;
        }

        req_sects = min_t(sector_t, nr_sects, max_discard_sectors);

        /*
         * 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;
        if (req_sects < nr_sects && (end_sect & mask) != alignment) {
            end_sect =
                round_down(end_sect - alignment, granularity)
                + alignment;
            req_sects = end_sect - sector;
        }

        bio->bi_sector = sector;
        bio->bi_end_io = bio_batch_end_io;
        bio->bi_bdev = bdev;
        bio->bi_private = &bb;

        bio->bi_size = req_sects << 9;
        nr_sects -= req_sects;
        sector = end_sect;

        atomic_inc(&bb.done);
        submit_bio(type, bio);
    }

    /* Wait for bios in-flight */
    if (!atomic_dec_and_test(&bb.done))
        wait_for_completion(&wait);

    if (!test_bit(BIO_UPTODATE, &bb.flags))
        ret = -EIO;

    return ret;
}
EXPORT_SYMBOL(blkdev_issue_discard);

int blkdev_issue_write_same(struct block_device *bdev, sector_t sector,
                sector_t nr_sects, gfp_t gfp_mask,
                struct page *page)
{
    DECLARE_COMPLETION_ONSTACK(wait);
    struct request_queue *q = bdev_get_queue(bdev);
    unsigned int max_write_same_sectors;
    struct bio_batch bb;
    struct bio *bio;
    int ret = 0;

    if (!q)
        return -ENXIO;

    max_write_same_sectors = q->limits.max_write_same_sectors;

    if (max_write_same_sectors == 0)
        return -EOPNOTSUPP;

    atomic_set(&bb.done, 1);
    bb.flags = 1 << BIO_UPTODATE;
    bb.wait = &wait;

    while (nr_sects) {
        bio = bio_alloc(gfp_mask, 1);
        if (!bio) {
            ret = -ENOMEM;
            break;
        }

        bio->bi_sector = sector;
        bio->bi_end_io = bio_batch_end_io;
        bio->bi_bdev = bdev;
        bio->bi_private = &bb;
        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);

        if (nr_sects > max_write_same_sectors) {
            bio->bi_size = max_write_same_sectors << 9;
            nr_sects -= max_write_same_sectors;
            sector += max_write_same_sectors;
        } else {
            bio->bi_size = nr_sects << 9;
            nr_sects = 0;
        }

        atomic_inc(&bb.done);
        submit_bio(REQ_WRITE | REQ_WRITE_SAME, bio);
    }

    /* Wait for bios in-flight */
    if (!atomic_dec_and_test(&bb.done))
        wait_for_completion(&wait);

    if (!test_bit(BIO_UPTODATE, &bb.flags))
        ret = -ENOTSUPP;

    return ret;
}
EXPORT_SYMBOL(blkdev_issue_write_same);

int __blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
            sector_t nr_sects, gfp_t gfp_mask)
{
    int ret;
    struct bio *bio;
    struct bio_batch bb;
    unsigned int sz;
    DECLARE_COMPLETION_ONSTACK(wait);

    atomic_set(&bb.done, 1);
    bb.flags = 1 << BIO_UPTODATE;
    bb.wait = &wait;

    ret = 0;
    while (nr_sects != 0) {
        bio = bio_alloc(gfp_mask,
                min(nr_sects, (sector_t)BIO_MAX_PAGES));
        if (!bio) {
            ret = -ENOMEM;
            break;
        }

        bio->bi_sector = sector;
        bio->bi_bdev   = bdev;
        bio->bi_end_io = bio_batch_end_io;
        bio->bi_private = &bb;

        while (nr_sects != 0) {
            sz = min((sector_t) PAGE_SIZE >> 9 , nr_sects);
            ret = bio_add_page(bio, ZERO_PAGE(0), sz << 9, 0);
            nr_sects -= ret >> 9;
            sector += ret >> 9;
            if (ret < (sz << 9))
                break;
        }
        ret = 0;
        atomic_inc(&bb.done);
        submit_bio(WRITE, bio);
    }

    /* Wait for bios in-flight */
    if (!atomic_dec_and_test(&bb.done))
        wait_for_completion(&wait);

    if (!test_bit(BIO_UPTODATE, &bb.flags))
        /* One of bios in the batch was completed with error.*/
        ret = -EIO;

    return ret;
}

int blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
             sector_t nr_sects, gfp_t gfp_mask)
{
    if (bdev_write_same(bdev)) {
        unsigned char bdn[BDEVNAME_SIZE];

        if (!blkdev_issue_write_same(bdev, sector, nr_sects, gfp_mask,
                         ZERO_PAGE(0)))
            return 0;

        bdevname(bdev, bdn);
        pr_err("%s: WRITE SAME failed. Manually zeroing.\n", bdn);
    }

    return __blkdev_issue_zeroout(bdev, sector, nr_sects, gfp_mask);
}
EXPORT_SYMBOL(blkdev_issue_zeroout);