1 files changed, 114 insertions, 0 deletions

diff --git a/block/blk-lib.c b/block/blk-lib.c
new file mode 100644
index 000000000000..0dc438812d81
--- /dev/null
+++ b/block/blk-lib.c
@@ -0,0 +1,114 @@
+/*
+ * 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"
+
+static void blkdev_discard_end_io(struct bio *bio, int err)
+{
+        if (err) {
+                if (err == -EOPNOTSUPP)
+                        set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
+                clear_bit(BIO_UPTODATE, &bio->bi_flags);
+        }
+
+        if (bio->bi_private)
+                complete(bio->bi_private);
+        __free_page(bio_page(bio));
+
+        bio_put(bio);
+}
+
+/**
+ * blkdev_issue_discard - queue a discard
+ * @bdev:       blockdev to issue discard for
+ * @sector:     start sector
+ * @nr_sects:   number of sectors to discard
+ * @gfp_mask:   memory allocation flags (for bio_alloc)
+ * @flags:      BLKDEV_IFL_* flags to control behaviour
+ *
+ * Description:
+ *    Issue a discard request for the sectors in question.
+ */
+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 = flags & BLKDEV_IFL_BARRIER ?
+                DISCARD_BARRIER : DISCARD_NOBARRIER;
+        struct bio *bio;
+        struct page *page;
+        int ret = 0;
+
+        if (!q)
+                return -ENXIO;
+
+        if (!blk_queue_discard(q))
+                return -EOPNOTSUPP;
+
+        while (nr_sects && !ret) {
+                unsigned int sector_size = q->limits.logical_block_size;
+                unsigned int max_discard_sectors =
+                        min(q->limits.max_discard_sectors, UINT_MAX >> 9);
+
+                bio = bio_alloc(gfp_mask, 1);
+                if (!bio)
+                        goto out;
+                bio->bi_sector = sector;
+                bio->bi_end_io = blkdev_discard_end_io;
+                bio->bi_bdev = bdev;
+                if (flags & BLKDEV_IFL_WAIT)
+                        bio->bi_private = &wait;
+
+                /*
+                 * Add a zeroed one-sector payload as that's what
+                 * our current implementations need.  If we'll ever need
+                 * more the interface will need revisiting.
+                 */
+                page = alloc_page(gfp_mask | __GFP_ZERO);
+                if (!page)
+                        goto out_free_bio;
+                if (bio_add_pc_page(q, bio, page, sector_size, 0) < sector_size)
+                        goto out_free_page;
+
+                /*
+                 * And override the bio size - the way discard works we
+                 * touch many more blocks on disk than the actual payload
+                 * length.
+                 */
+                if (nr_sects > max_discard_sectors) {
+                        bio->bi_size = max_discard_sectors << 9;
+                        nr_sects -= max_discard_sectors;
+                        sector += max_discard_sectors;
+                } else {
+                        bio->bi_size = nr_sects << 9;
+                        nr_sects = 0;
+                }
+
+                bio_get(bio);
+                submit_bio(type, bio);
+
+                if (flags & BLKDEV_IFL_WAIT)
+                        wait_for_completion(&wait);
+
+                if (bio_flagged(bio, BIO_EOPNOTSUPP))
+                        ret = -EOPNOTSUPP;
+                else if (!bio_flagged(bio, BIO_UPTODATE))
+                        ret = -EIO;
+                bio_put(bio);
+        }
+        return ret;
+out_free_page:
+        __free_page(page);
+out_free_bio:
+        bio_put(bio);
+out:
+        return -ENOMEM;
+}
+EXPORT_SYMBOL(blkdev_issue_discard);