One of the common application for the file systems and drivers to map
the buffer to the bio and issue I/Os on the block device.
This is a prep patch which adds two helper functions for block layer
which allows file-systems and the drivers to map data buffer on to the
bios and issue bios synchronously using blkdev_issue_rw() or
asynchronously using __blkdev_issue_rw().
Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@xxxxxxx>
---
block/blk-lib.c | 105 +++++++++++++++++++++++++++++++++++++++++
include/linux/blkdev.h | 7 +++
2 files changed, 112 insertions(+)
diff --git a/block/blk-lib.c b/block/blk-lib.c
index 5f2c429d4378..451c367fc0d6 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -405,3 +405,108 @@ int blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
return ret;
}
EXPORT_SYMBOL(blkdev_issue_zeroout);
+
+/**
+ * __blkdev_ssue_rw - issue read/write bios from buffer asynchronously
+ * @bdev: blockdev to read/write
+ * @buf: data buffer
+ * @sector: start sector
+ * @nr_sects: number of sectors
+ * @op: REQ_OP_READ or REQ_OP_WRITE
+ * @opf: flags
+ * @gfp_mask: memory allocation flags (for bio_alloc)
+ * @biop: pointer to anchor bio
+ *
+ * Description:
+ * Generic helper function to map data buffer into bios for read and write ops.
+ * Returns pointer to the anchored last bio for caller to submit asynchronously
+ * or synchronously.
+ */
+int __blkdev_issue_rw(struct block_device *bdev, char *buf, sector_t sector,
+ sector_t nr_sects, unsigned op, unsigned opf,
+ gfp_t gfp_mask, struct bio **biop)
+{
+ bool vm = is_vmalloc_addr(buf) ? true : false;
+ struct bio *bio = *biop;
+ unsigned int nr_pages;
+ struct page *page;
+ unsigned int off;
+ unsigned int len;
+ int bi_size;
+
+ if (!bdev_get_queue(bdev))
+ return -ENXIO;
+
+ if (bdev_read_only(bdev))
+ return -EPERM;
+
+ if (!(op == REQ_OP_READ || op == REQ_OP_WRITE))
+ return -EINVAL;
+
+ while (nr_sects != 0) {
+ nr_pages = __blkdev_sectors_to_bio_pages(nr_sects);
+
+ bio = blk_next_bio(bio, nr_pages, gfp_mask);
+ bio->bi_iter.bi_sector = sector;
+ bio_set_dev(bio, bdev);
+ bio_set_op_attrs(bio, op, 0);
+
+ while (nr_sects != 0) {
+ off = offset_in_page(buf);
+ page = vm ? vmalloc_to_page(buf) : virt_to_page(buf);
+ len = min((sector_t) PAGE_SIZE, nr_sects << 9);
+
+ bi_size = bio_add_page(bio, page, len, off);
+
+ nr_sects -= bi_size >> 9;
+ sector += bi_size >> 9;
+ buf += bi_size;
+
+ if (bi_size < len)
+ break;
+ }
+ cond_resched();
+ }
+ *biop = bio;
+ return 0;
+}
+EXPORT_SYMBOL_GPL(__blkdev_issue_rw);
+
+/**
+ * blkdev_execute_rw_sync - issue read/write bios from buffer synchronously
+ * @bdev: blockdev to read/write
+ * @buf: data buffer
+ * @sector: start sector
+ * @count: number of bytes
+ * @op: REQ_OP_READ or REQ_OP_WRITE
+ * @opf: flags
+ * @gfp_mask: memory allocation flags (for bio_alloc)
+ *
+ * Description:
+ * Generic helper function to map data buffer buffer into bios for read and
+ * write requests.
+ */
+int blkdev_issue_rw(struct block_device *b, char *buf, sector_t sector,
+ unsigned count, unsigned op, unsigned opf, gfp_t mask)
+{
+ unsigned int is_vmalloc = is_vmalloc_addr(buf);
+ sector_t nr_sects = count >> 9;
+ struct bio *bio = NULL;
+ int error;
+
+ if (is_vmalloc && op == REQ_OP_WRITE)
+ flush_kernel_vmap_range(buf, count);
+
+ opf |= REQ_SYNC;
+ error = __blkdev_issue_rw(b, buf, sector, nr_sects, op, opf, mask, &bio);
+ if (!error && bio) {
+ error = submit_bio_wait(bio);
+ bio_put(bio);
+ }
+
+ if (is_vmalloc && op == REQ_OP_READ)
+ invalidate_kernel_vmap_range(buf, count);
+
+ return error;
+}
+EXPORT_SYMBOL_GPL(blkdev_issue_rw);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 32868fbedc9e..cb315b301ad9 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1248,6 +1248,13 @@ static inline int sb_issue_zeroout(struct super_block *sb, sector_t block,
gfp_mask, 0);
}
+extern int __blkdev_issue_rw(struct block_device *bdev, char *buf,
+ sector_t sector, sector_t nr_sects, unsigned op,
+ unsigned opf, gfp_t gfp_mask, struct bio **biop);
+extern int blkdev_issue_rw(struct block_device *b, char *buf, sector_t sector,
+ unsigned count, unsigned op, unsigned opf,
+ gfp_t mask);
+
extern int blk_verify_command(unsigned char *cmd, fmode_t mode);
enum blk_default_limits {
--
2.22.1
