dm snapshot: support barriers in snapshot merge target
Sets num_flush_requests=2 to support flushing both the origin and cow devices used by the snapshot-merge target. Also, snapshot_ctr() now gets the origin device using FMODE_WRITE if the target is snapshot-merge (which writes to the origin device). Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
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@ -709,7 +709,8 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
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int i;
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int r = -EINVAL;
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char *origin_path, *cow_path;
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unsigned args_used;
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unsigned args_used, num_flush_requests = 1;
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fmode_t origin_mode = FMODE_READ;
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if (argc != 4) {
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ti->error = "requires exactly 4 arguments";
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@ -717,6 +718,11 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
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goto bad;
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}
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if (dm_target_is_snapshot_merge(ti)) {
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num_flush_requests = 2;
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origin_mode = FMODE_WRITE;
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}
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origin_path = argv[0];
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argv++;
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argc--;
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@ -750,7 +756,7 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
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argv += args_used;
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argc -= args_used;
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r = dm_get_device(ti, origin_path, 0, ti->len, FMODE_READ, &s->origin);
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r = dm_get_device(ti, origin_path, 0, ti->len, origin_mode, &s->origin);
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if (r) {
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ti->error = "Cannot get origin device";
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goto bad_origin;
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@ -801,7 +807,7 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
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INIT_WORK(&s->queued_bios_work, flush_queued_bios);
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ti->private = s;
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ti->num_flush_requests = 1;
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ti->num_flush_requests = num_flush_requests;
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/* Add snapshot to the list of snapshots for this origin */
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/* Exceptions aren't triggered till snapshot_resume() is called */
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@ -1326,6 +1332,15 @@ static int snapshot_merge_map(struct dm_target *ti, struct bio *bio,
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int r = DM_MAPIO_REMAPPED;
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chunk_t chunk;
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if (unlikely(bio_empty_barrier(bio))) {
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if (!map_context->flush_request)
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bio->bi_bdev = s->origin->bdev;
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else
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bio->bi_bdev = s->cow->bdev;
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map_context->ptr = NULL;
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return DM_MAPIO_REMAPPED;
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}
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chunk = sector_to_chunk(s->store, bio->bi_sector);
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down_read(&s->lock);
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