by Dmitry Monakhov

[permalink] [raw]

Subject: [PATCH 4/4] 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 <[email protected]>
---
block/blk-lib.c | 118 ++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/blkdev.h | 3 +-
2 files changed, 120 insertions(+), 1 deletions(-)

diff --git a/block/blk-lib.c b/block/blk-lib.c
index 0dc4388..886c3f9 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);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 59b9aed..3ac2bd2 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1008,7 +1008,8 @@ extern int blkdev_issue_flush(struct block_device *, gfp_t, sector_t *,
unsigned long);
extern int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
sector_t nr_sects, gfp_t gfp_mask, unsigned long flags);
-
+extern int blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
+ sector_t nr_sects, gfp_t gfp_mask, unsigned long flags);
static inline int sb_issue_discard(struct super_block *sb,
sector_t block, sector_t nr_blocks)
{
--
1.6.6.1