dm ebs: pass discards down to underlying device

Make use of dm_bufio_issue_discard() to pass discards down to the
underlying device.

Signed-off-by: Heinz Mauelshagen <heinzm@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

diff --git a/drivers/md/dm-ebs-target.c b/drivers/md/dm-ebs-target.c
index c2bd21f..ae3f5fa 100644 (file)
--- a/drivers/md/dm-ebs-target.c
+++ b/drivers/md/dm-ebs-target.c
@@ -132,16 +132,43 @@ static int __ebs_rw_bio(struct ebs_c *ec, int rw, struct bio *bio)
        return r;
 }
 
-/* 'Discard' blocks, i.e. release them from the bufio cache. */
-static int __ebs_forget_bio(struct ebs_c *ec, struct bio *bio)
+/*
+ * Discard bio's blocks, i.e. pass discards down.
+ *
+ * Avoid discarding partial blocks at beginning and end;
+ * return 0 in case no blocks can be discarded as a result.
+ */
+static int __ebs_discard_bio(struct ebs_c *ec, struct bio *bio)
+{
+       sector_t block, blocks, sector = bio->bi_iter.bi_sector;
+
+       block = __sector_to_block(ec, sector);
+       blocks = __nr_blocks(ec, bio);
+
+       /*
+        * Partial first underlying block (__nr_blocks() may have
+        * resulted in one block).
+        */
+       if (__block_mod(sector, ec->u_bs)) {
+               block++;
+               blocks--;
+       }
+
+       /* Partial last underlying block if any. */
+       if (blocks && __block_mod(bio_end_sector(bio), ec->u_bs))
+               blocks--;
+
+       return blocks ? dm_bufio_issue_discard(ec->bufio, block, blocks) : 0;
+}
+
+/* Release blocks them from the bufio cache. */
+static void __ebs_forget_bio(struct ebs_c *ec, struct bio *bio)
 {
        sector_t blocks, sector = bio->bi_iter.bi_sector;
 
        blocks = __nr_blocks(ec, bio);
        for (; blocks--; sector += ec->u_bs)
                dm_bufio_forget(ec->bufio, __sector_to_block(ec, sector));
-
-       return 0;
 }
 
 /* Worker funtion to process incoming bios. */
@@ -183,8 +210,8 @@ static void __ebs_process_bios(struct work_struct *ws)
                        write = true;
                        r = __ebs_rw_bio(ec, WRITE, bio);
                } else if (bio_op(bio) == REQ_OP_DISCARD) {
-                       /* FIXME: (optionally) call dm_bufio_discard_buffers() once upstream. */
-                       r = __ebs_forget_bio(ec, bio);
+                       __ebs_forget_bio(ec, bio);
+                       r = __ebs_discard_bio(ec, bio);
                }
 
                if (r < 0)
@@ -409,7 +436,7 @@ static int ebs_iterate_devices(struct dm_target *ti,
 
 static struct target_type ebs_target = {
        .name            = "ebs",
-       .version         = {1, 0, 0},
+       .version         = {1, 0, 1},
        .features        = DM_TARGET_PASSES_INTEGRITY,
        .module          = THIS_MODULE,
        .ctr             = ebs_ctr,