[PATCH] dm snapshot: tidy snapshot_map (ba40a2aa) · Commits · 戴 / test

drivers/md/dm-snap.c

+26 −46

Original line number	Diff line number	Diff line
		@@ -851,7 +851,6 @@ static int snapshot_map(struct dm_target ti, struct bio bio,
		{
		struct exception *e;
		struct dm_snapshot s = (struct dm_snapshot ) ti->private;
		int copy_needed = 0;
		int r = 1;
		chunk_t chunk;
		struct pending_exception *pe = NULL;
		@@ -866,13 +865,6 @@ static int snapshot_map(struct dm_target ti, struct bio bio,
		if (unlikely(bio_barrier(bio)))
		return -EOPNOTSUPP;

		/*
		* Write to snapshot - higher level takes care of RW/RO
		* flags so we should only get this if we are
		* writeable.
		*/
		if (bio_rw(bio) == WRITE) {

		/* FIXME: should only take write lock if we need
		* to copy an exception */
		down_write(&s->lock);
		@@ -889,6 +881,12 @@ static int snapshot_map(struct dm_target ti, struct bio bio,
		goto out_unlock;
		}

		/*
		* Write to snapshot - higher level takes care of RW/RO
		* flags so we should only get this if we are
		* writeable.
		*/
		if (bio_rw(bio) == WRITE) {
		pe = __find_pending_exception(s, bio);
		if (!pe) {
		__invalidate_snapshot(s, pe, -ENOMEM);
		@@ -899,45 +897,27 @@ static int snapshot_map(struct dm_target ti, struct bio bio,
		remap_exception(s, &pe->e, bio);
		bio_list_add(&pe->snapshot_bios, bio);

		r = 0;

		if (!pe->started) {
		/* this is protected by snap->lock */
		pe->started = 1;
		copy_needed = 1;
		}

		r = 0;

		out_unlock:
		up_write(&s->lock);

		if (copy_needed)
		start_copy(pe);
		} else {
		goto out;
		}
		} else
		/*
		* FIXME: this read path scares me because we
		* always use the origin when we have a pending
		* exception. However I can't think of a
		* situation where this is wrong - ejt.
		*/

		/* Do reads */
		down_read(&s->lock);

		if (!s->valid) {
		up_read(&s->lock);
		return -EIO;
		}

		/* See if it it has been remapped */
		e = lookup_exception(&s->complete, chunk);
		if (e)
		remap_exception(s, e, bio);
		else
		bio->bi_bdev = s->origin->bdev;

		up_read(&s->lock);
		}

		out_unlock:
		up_write(&s->lock);
		out:
		return r;
		}

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