[PATCH] dm: mirror sector offset fix

The device-mapper core does not perform any remapping of bios before passing
them to the targets.  If a particular mapping begins part-way into a device,
targets obtain the sector relative to the start of the mapping by subtracting
ti->begin.

The dm-raid1 target didn't do this everywhere: this patch fixes it, taking
care to subtract ti->begin exactly once for each bio.

[akpm: too late for 2.6.17 - suitable for 2.6.17.x after it has settled]

Signed-off-by: Neil Brown <neilb@suse.de>
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>

1 files changed, 32 insertions, 31 deletions

diff --git a/drivers/md/dm-raid1.c b/drivers/md/dm-raid1.c
index 4ad269e66525..346f3a59e776 100644
--- a/drivers/md/dm-raid1.c
+++ b/drivers/md/dm-raid1.c
@@ -106,12 +106,42 @@ struct region {
         struct bio_list delayed_bios;
 };
 
+
+/*-----------------------------------------------------------------
+ * Mirror set structures.
+ *---------------------------------------------------------------*/
+struct mirror {
+        atomic_t error_count;
+        struct dm_dev *dev;
+        sector_t offset;
+};
+
+struct mirror_set {
+        struct dm_target *ti;
+        struct list_head list;
+        struct region_hash rh;
+        struct kcopyd_client *kcopyd_client;
+
+        spinlock_t lock;        /* protects the next two lists */
+        struct bio_list reads;
+        struct bio_list writes;
+
+        /* recovery */
+        region_t nr_regions;
+        int in_sync;
+
+        struct mirror *default_mirror;  /* Default mirror */
+
+        unsigned int nr_mirrors;
+        struct mirror mirror[0];
+};
+
 /*
  * Conversion fns
  */
 static inline region_t bio_to_region(struct region_hash *rh, struct bio *bio)
 {
-        return bio->bi_sector >> rh->region_shift;
+        return (bio->bi_sector - rh->ms->ti->begin) >> rh->region_shift;
 }
 
 static inline sector_t region_to_sector(struct region_hash *rh, region_t region)
@@ -539,35 +569,6 @@ static void rh_start_recovery(struct region_hash *rh)
         wake();
 }
 
-/*-----------------------------------------------------------------
- * Mirror set structures.
- *---------------------------------------------------------------*/
-struct mirror {
-        atomic_t error_count;
-        struct dm_dev *dev;
-        sector_t offset;
-};
-
-struct mirror_set {
-        struct dm_target *ti;
-        struct list_head list;
-        struct region_hash rh;
-        struct kcopyd_client *kcopyd_client;
-
-        spinlock_t lock;        /* protects the next two lists */
-        struct bio_list reads;
-        struct bio_list writes;
-
-        /* recovery */
-        region_t nr_regions;
-        int in_sync;
-
-        struct mirror *default_mirror;  /* Default mirror */
-
-        unsigned int nr_mirrors;
-        struct mirror mirror[0];
-};
-
 /*
  * Every mirror should look like this one.
  */
@@ -1113,7 +1114,7 @@ static int mirror_map(struct dm_target *ti, struct bio *bio,
         struct mirror *m;
         struct mirror_set *ms = ti->private;
 
-        map_context->ll = bio->bi_sector >> ms->rh.region_shift;
+        map_context->ll = bio_to_region(&ms->rh, bio);
 
         if (rw == WRITE) {
                 queue_bio(ms, bio, rw);