[PATCH] dm: bio split bvec fix

The code that handles bios that span table target boundaries by breaking
them up into smaller bios will not split an individual struct bio_vec into
more than two pieces.  Sometimes more than that are required.

This patch adds a loop to break the second piece up into as many pieces as
are necessary.

Cc: "Abhishek Gupta" <abhishekgupt@gmail.com>
Cc: Dan Smith <danms@us.ibm.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 88d6020..26b08ee 100644 (file)
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -533,30 +533,35 @@ static void __clone_and_map(struct clone_info *ci)
 
        } else {
                /*
-                * Create two copy bios to deal with io that has
-                * been split across a target.
+                * Handle a bvec that must be split between two or more targets.
                 */
                struct bio_vec *bv = bio->bi_io_vec + ci->idx;
+               sector_t remaining = to_sector(bv->bv_len);
+               unsigned int offset = 0;
 
-               clone = split_bvec(bio, ci->sector, ci->idx,
-                                  bv->bv_offset, max);
-               __map_bio(ti, clone, tio);
+               do {
+                       if (offset) {
+                               ti = dm_table_find_target(ci->map, ci->sector);
+                               max = max_io_len(ci->md, ci->sector, ti);
 
-               ci->sector += max;
-               ci->sector_count -= max;
-               ti = dm_table_find_target(ci->map, ci->sector);
-
-               len = to_sector(bv->bv_len) - max;
-               clone = split_bvec(bio, ci->sector, ci->idx,
-                                  bv->bv_offset + to_bytes(max), len);
-               tio = alloc_tio(ci->md);
-               tio->io = ci->io;
-               tio->ti = ti;
-               memset(&tio->info, 0, sizeof(tio->info));
-               __map_bio(ti, clone, tio);
+                               tio = alloc_tio(ci->md);
+                               tio->io = ci->io;
+                               tio->ti = ti;
+                               memset(&tio->info, 0, sizeof(tio->info));
+                       }
+
+                       len = min(remaining, max);
+
+                       clone = split_bvec(bio, ci->sector, ci->idx,
+                                          bv->bv_offset + offset, len);
+
+                       __map_bio(ti, clone, tio);
+
+                       ci->sector += len;
+                       ci->sector_count -= len;
+                       offset += to_bytes(len);
+               } while (remaining -= len);
 
-               ci->sector += len;
-               ci->sector_count -= len;
                ci->idx++;
        }
 }