blkdev: add blkdev_issue_zeroout helper function

- Add bio_batch helper primitive. This is rather generic primitive
  for submitting/waiting a complex request which consists of several
  bios.
- blkdev_issue_zeroout() generate number of zero filed write bios.

Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 118 insertions, 0 deletions

diff --git a/block/blk-lib.c b/block/blk-lib.c
index 0dc438812d81..886c3f9e1be4 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -112,3 +112,121 @@ out:
         return -ENOMEM;
 }
 EXPORT_SYMBOL(blkdev_issue_discard);
+
+struct bio_batch
+{
+        atomic_t                done;
+        unsigned long           flags;
+        struct completion       *wait;
+        bio_end_io_t            *end_io;
+};
+
+static void bio_batch_end_io(struct bio *bio, int err)
+{
+        struct bio_batch *bb = bio->bi_private;
+        if (err) {
+                if (err == -EOPNOTSUPP)
+                        set_bit(BIO_EOPNOTSUPP, &bb->flags);
+                else
+                        clear_bit(BIO_UPTODATE, &bb->flags);
+        }
+        if (bb) {
+                if (bb->end_io)
+                        bb->end_io(bio, err);
+                atomic_inc(&bb->done);
+                complete(bb->wait);
+        }
+        bio_put(bio);
+}
+
+/**
+ * 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)
+ * @flags:      BLKDEV_IFL_* flags to control behaviour
+ *
+ * Description:
+ *  Generate and issue number of bios with zerofiled pages.
+ *  Send barrier at the beginning and at the end if requested. This guarantie
+ *  correct request ordering. Empty barrier allow us to avoid post queue flush.
+ */
+
+int blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
+                        sector_t nr_sects, gfp_t gfp_mask, unsigned long flags)
+{
+        int ret = 0;
+        struct bio *bio;
+        struct bio_batch bb;
+        unsigned int sz, issued = 0;
+        DECLARE_COMPLETION_ONSTACK(wait);
+
+        atomic_set(&bb.done, 0);
+        bb.flags = 1 << BIO_UPTODATE;
+        bb.wait = &wait;
+        bb.end_io = NULL;
+
+        if (flags & BLKDEV_IFL_BARRIER) {
+                /* issue async barrier before the data */
+                ret = blkdev_issue_flush(bdev, gfp_mask, NULL, 0);
+                if (ret)
+                        return ret;
+        }
+submit:
+        while (nr_sects != 0) {
+                bio = bio_alloc(gfp_mask,
+                                min(nr_sects, (sector_t)BIO_MAX_PAGES));
+                if (!bio)
+                        break;
+
+                bio->bi_sector = sector;
+                bio->bi_bdev   = bdev;
+                bio->bi_end_io = bio_batch_end_io;
+                if (flags & BLKDEV_IFL_WAIT)
+                        bio->bi_private = &bb;
+
+                while(nr_sects != 0) {
+                        sz = min(PAGE_SIZE >> 9 , nr_sects);
+                        if (sz == 0)
+                                /* bio has maximum size possible */
+                                break;
+                        ret = bio_add_page(bio, ZERO_PAGE(0), sz << 9, 0);
+                        nr_sects -= ret >> 9;
+                        sector += ret >> 9;
+                        if (ret < (sz << 9))
+                                break;
+                }
+                issued++;
+                submit_bio(WRITE, bio);
+        }
+        /*
+         * When all data bios are in flight. Send final barrier if requeted.
+         */
+        if (nr_sects == 0 && flags & BLKDEV_IFL_BARRIER)
+                ret = blkdev_issue_flush(bdev, gfp_mask, NULL,
+                                        flags & BLKDEV_IFL_WAIT);
+
+
+        if (flags & BLKDEV_IFL_WAIT)
+                /* Wait for bios in-flight */
+                while ( issued != atomic_read(&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;
+
+        if (ret)
+                goto out;
+
+        if (test_bit(BIO_EOPNOTSUPP, &bb.flags)) {
+                ret = -EOPNOTSUPP;
+                goto out;
+        }
+        if (nr_sects != 0)
+                goto submit;
+out:
+        return ret;
+}
+EXPORT_SYMBOL(blkdev_issue_zeroout);