[PATCH v4 11/13] dm snapshot: make exceptions in other snapshots when merging

Mike Snitzer
2009-11-20T20:28:50Z

When there is one merging snapshot and other non-merging snapshots,
snapshot_merge_process() must make exceptions in the non-merging
snapshots.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
---
drivers/md/dm-snap.c | 32 +++++++++++++++++++++++++++++++-
1 files changed, 31 insertions(+), 1 deletions(-)

diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index e41be70..2b5b083 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -255,6 +255,8 @@ struct origin {
static struct list_head *_origins;
static struct rw_semaphore _origins_lock;

+static DECLARE_WAIT_QUEUE_HEAD(_pending_exception_done);
+
static int init_origin_hash(void)
{
int i;
@@ -742,13 +744,18 @@ static int init_hash_tables(struct dm_snapshot *s)
static void flush_bios(struct bio *bio);
static void error_bios(struct bio *bio);

+static int __origin_write(struct list_head *snapshots,
+ sector_t sector, struct bio *bio);
+
static void merge_callback(int read_err, unsigned long write_err,
void *context);

static void snapshot_merge_process(struct dm_snapshot *s)
{
int r;
- chunk_t old_chunk, new_chunk;
+ chunk_t old_chunk, new_chunk, n;
+ struct origin *o;
+ int must_wait;
struct dm_io_region src, dest;

BUG_ON(!s->merge_running);
@@ -779,6 +786,27 @@ static void snapshot_merge_process(struct dm_snapshot *s)
src.sector = chunk_to_sector(s->store, new_chunk);
src.count = dest.count;

+test_again:
+ /* Reallocate other snapshots */
+ must_wait = 0;
+ /*
+ * Merging snapshot already has the origin's __minimum_chunk_size()
+ * stored in split_io (see: snapshot_merge_resume); avoid rediscovery
+ */
+ BUG_ON(!s->ti->split_io);
+ down_read(&_origins_lock);
+ o = __lookup_origin(s->origin->bdev);
+ for (n = 0; n < s->store->chunk_size; n += s->ti->split_io) {
+ r = __origin_write(&o->snapshots, dest.sector + n, NULL);
+ if (r == DM_MAPIO_SUBMITTED)
+ must_wait = 1;
+ }
+ up_read(&_origins_lock);
+ if (must_wait) {
+ sleep_on_timeout(&_pending_exception_done, HZ / 100 + 1);
+ goto test_again;
+ }
+
down_write(&s->lock);
s->merge_write_interlock = old_chunk;
s->merge_write_interlock_n = 1;
@@ -1301,6 +1329,8 @@ static void pending_complete(struct dm_snap_pending_exception *pe, int success)
origin_bios = bio_list_get(&pe->origin_bios);
free_pending_exception(pe);

+ wake_up_all(&_pending_exception_done);
+
up_write(&s->lock);

/* Submit any pending write bios */
--
1.6.5.2