[PATCH] Old kernel patch for remapping rehabilitated

[Alan D. Brunelle]

From:  <[EMAIL PROTECTED]>

Fix remap handling by blktrace

This patch provides more information concerning REMAP operations on block
IOs. The additional information provides clearer details at the user level,
and supports post-processing analysis in btt.

o  Adds in partition remaps on the same device.
o  Fixed up the remap information in DM to be in the right order
o  Sent up mapped-from and mapped-to device information
---

 block/ll_rw_blk.c            |    4 ++++
 drivers/md/dm.c              |    4 ++--
 include/linux/blktrace_api.h |    3 ++-
 3 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index 38c293b..e6fdfd8 100644
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -3037,6 +3037,10 @@ static inline void blk_partition_remap(struct bio *bio)
 
                bio->bi_sector += p->start_sect;
                bio->bi_bdev = bdev->bd_contains;
+
+               blk_add_trace_remap(bdev_get_queue(bio->bi_bdev), bio,
+                                   bdev->bd_dev, bio->bi_sector,
+                                   bio->bi_sector - p->start_sect);
        }
 }
 
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 3668b17..4dacf6b 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -584,8 +584,8 @@ static void __map_bio(struct dm_target *ti, struct bio 
*clone,
                /* the bio has been remapped so dispatch it */
 
                blk_add_trace_remap(bdev_get_queue(clone->bi_bdev), clone,
-                                   tio->io->bio->bi_bdev->bd_dev, sector,
-                                   clone->bi_sector);
+                                   tio->io->bio->bi_bdev->bd_dev,
+                                   clone->bi_sector, sector);
 
                generic_make_request(clone);
        } else if (r < 0 || r == DM_MAPIO_REQUEUE) {
diff --git a/include/linux/blktrace_api.h b/include/linux/blktrace_api.h
index 3680ff9..9e2e498 100644
--- a/include/linux/blktrace_api.h
+++ b/include/linux/blktrace_api.h
@@ -105,7 +105,7 @@ struct blk_io_trace {
  */
 struct blk_io_trace_remap {
        __be32 device;
-       u32 __pad;
+       __be32 device_from;
        __be64 sector;
 };
 
@@ -272,6 +272,7 @@ static inline void blk_add_trace_remap(struct request_queue 
*q, struct bio *bio,
                return;
 
        r.device = cpu_to_be32(dev);
+       r.device_from = cpu_to_be32(bio->bi_bdev->bd_dev);
        r.sector = cpu_to_be64(to);
 
        __blk_add_trace(bt, from, bio->bi_size, bio->bi_rw, BLK_TA_REMAP, 
!bio_flagged(bio, BIO_UPTODATE), sizeof(r), &r);