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dm snapshot: do not use map_context 

Eliminate struct map_info from dm-snap.

map_info->ptr was used in dm-snap to indicate if the bio was tracked.
If map_info->ptr was non-NULL, the bio was linked in tracked_chunk_hash.

This patch removes the use of map_info->ptr. We determine if the bio was
tracked based on hlist_unhashed(&c->node). If hlist_unhashed is true,
the bio is not tracked, if it is false, the bio is tracked.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
This commit is contained in:
Mikulas Patocka 2012-12-21 20:23:41 +00:00 committed by Alasdair G Kergon
parent 59c3d2c6a1
commit ee18026ac6
1 changed files with 23 additions and 13 deletions
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36
drivers/md/dm-snap.c
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@ -190,9 +190,19 @@ struct dm_snap_tracked_chunk {
chunk_t chunk;
};
static struct dm_snap_tracked_chunk *track_chunk(struct dm_snapshot *s,
struct bio *bio,
chunk_t chunk)
static void init_tracked_chunk(struct bio *bio)
{
struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
INIT_HLIST_NODE(&c->node);
}
static bool is_bio_tracked(struct bio *bio)
{
struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
return !hlist_unhashed(&c->node);
}
static void track_chunk(struct dm_snapshot *s, struct bio *bio, chunk_t chunk)
{
struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
@ -202,13 +212,11 @@ static struct dm_snap_tracked_chunk *track_chunk(struct dm_snapshot *s,
hlist_add_head(&c->node,
&s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)]);
spin_unlock_irq(&s->tracked_chunk_lock);
return c;
}
static void stop_tracking_chunk(struct dm_snapshot *s,
struct dm_snap_tracked_chunk *c)
static void stop_tracking_chunk(struct dm_snapshot *s, struct bio *bio)
{
struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
unsigned long flags;
spin_lock_irqsave(&s->tracked_chunk_lock, flags);
@ -1568,6 +1576,8 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio,
chunk_t chunk;
struct dm_snap_pending_exception *pe = NULL;
init_tracked_chunk(bio);
if (bio->bi_rw & REQ_FLUSH) {
bio->bi_bdev = s->cow->bdev;
return DM_MAPIO_REMAPPED;
@ -1652,7 +1662,7 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio,
}
} else {
bio->bi_bdev = s->origin->bdev;
map_context->ptr = track_chunk(s, bio, chunk);
track_chunk(s, bio, chunk);
}
out_unlock:
@ -1681,12 +1691,13 @@ static int snapshot_merge_map(struct dm_target *ti, struct bio *bio,
int r = DM_MAPIO_REMAPPED;
chunk_t chunk;
init_tracked_chunk(bio);
if (bio->bi_rw & REQ_FLUSH) {
if (!dm_bio_get_target_request_nr(bio))
bio->bi_bdev = s->origin->bdev;
else
bio->bi_bdev = s->cow->bdev;
map_context->ptr = NULL;
return DM_MAPIO_REMAPPED;
}
@ -1715,7 +1726,7 @@ static int snapshot_merge_map(struct dm_target *ti, struct bio *bio,
remap_exception(s, e, bio, chunk);
if (bio_rw(bio) == WRITE)
map_context->ptr = track_chunk(s, bio, chunk);
track_chunk(s, bio, chunk);
goto out_unlock;
}
@ -1737,10 +1748,9 @@ static int snapshot_end_io(struct dm_target *ti, struct bio *bio,
int error, union map_info *map_context)
{
struct dm_snapshot *s = ti->private;
struct dm_snap_tracked_chunk *c = map_context->ptr;
if (c)
stop_tracking_chunk(s, c);
if (is_bio_tracked(bio))
stop_tracking_chunk(s, bio);
return 0;
}