Commit d284f824 authored by Mikulas Patocka's avatar Mikulas Patocka Committed by Mike Snitzer
Browse files

dm writecache: support optional offset for start of device 



Add an optional parameter "start_sector" to allow the start of the
device to be offset by the specified number of 512-byte sectors.  The
sectors below this offset are not used by the writecache device and are
left to be used for disk labels and/or userspace metadata (e.g. lvm).

Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
parent 021c9179

Documentation/device-mapper/writecache.txt

+2 −0
Original line number Diff line number Diff line
@@ -15,6 +15,8 @@ Constructor parameters: 
   size)

5. the number of optional parameters (the parameters with an argument

   count as two)

	start_sector n		(default: 0)

		offset from the start of cache device in 512-byte sectors

	high_watermark n	(default: 50)

		start writeback when the number of used blocks reach this

		watermark

drivers/md/dm-writecache.c

+29 −14
Original line number Diff line number Diff line
@@ -136,6 +136,7 @@ struct dm_writecache { 
	struct dm_target *ti;

	struct dm_dev *dev;

	struct dm_dev *ssd_dev;

	sector_t start_sector;

	void *memory_map;

	uint64_t memory_map_size;

	size_t metadata_sectors;
@@ -293,6 +294,10 @@ static int persistent_memory_claim(struct dm_writecache *wc) 
	}



	dax_read_unlock(id);



	wc->memory_map += (size_t)wc->start_sector << SECTOR_SHIFT;

	wc->memory_map_size -= (size_t)wc->start_sector << SECTOR_SHIFT;



	return 0;

err3:

	kvfree(pages);
@@ -311,7 +316,7 @@ static int persistent_memory_claim(struct dm_writecache *wc) 
static void persistent_memory_release(struct dm_writecache *wc)

{

	if (wc->memory_vmapped)

		vunmap(wc->memory_map);

		vunmap(wc->memory_map - ((size_t)wc->start_sector << SECTOR_SHIFT));

}



static struct page *persistent_memory_page(void *addr)
@@ -359,7 +364,7 @@ static void *memory_data(struct dm_writecache *wc, struct wc_entry *e) 


static sector_t cache_sector(struct dm_writecache *wc, struct wc_entry *e)

{

	return wc->metadata_sectors +

	return wc->start_sector + wc->metadata_sectors +

		((sector_t)e->index << (wc->block_size_bits - SECTOR_SHIFT));

}
@@ -471,6 +476,7 @@ static void ssd_commit_flushed(struct dm_writecache *wc) 
		if (unlikely(region.sector + region.count > wc->metadata_sectors))

			region.count = wc->metadata_sectors - region.sector;



		region.sector += wc->start_sector;

		atomic_inc(&endio.count);

		req.bi_op = REQ_OP_WRITE;

		req.bi_op_flags = REQ_SYNC;
@@ -1946,14 +1952,6 @@ static int writecache_ctr(struct dm_target *ti, unsigned argc, char **argv) 
	}

	wc->memory_map_size = i_size_read(wc->ssd_dev->bdev->bd_inode);



	if (WC_MODE_PMEM(wc)) {

		r = persistent_memory_claim(wc);

		if (r) {

			ti->error = "Unable to map persistent memory for cache";

			goto bad;

		}

	}



	/*

	 * Parse the cache block size

	 */
@@ -1982,7 +1980,16 @@ static int writecache_ctr(struct dm_target *ti, unsigned argc, char **argv) 


	while (opt_params) {

		string = dm_shift_arg(&as), opt_params--;

		if (!strcasecmp(string, "high_watermark") && opt_params >= 1) {

		if (!strcasecmp(string, "start_sector") && opt_params >= 1) {

			unsigned long long start_sector;

			string = dm_shift_arg(&as), opt_params--;

			if (sscanf(string, "%llu%c", &start_sector, &dummy) != 1)

				goto invalid_optional;

			wc->start_sector = start_sector;

			if (wc->start_sector != start_sector ||

			    wc->start_sector >= wc->memory_map_size >> SECTOR_SHIFT)

				goto invalid_optional;

		} else if (!strcasecmp(string, "high_watermark") && opt_params >= 1) {

			string = dm_shift_arg(&as), opt_params--;

			if (sscanf(string, "%d%c", &high_wm_percent, &dummy) != 1)

				goto invalid_optional;
@@ -2039,12 +2046,20 @@ invalid_optional: 
		goto bad;

	}



	if (!WC_MODE_PMEM(wc)) {

	if (WC_MODE_PMEM(wc)) {

		r = persistent_memory_claim(wc);

		if (r) {

			ti->error = "Unable to map persistent memory for cache";

			goto bad;

		}

	} else {

		struct dm_io_region region;

		struct dm_io_request req;

		size_t n_blocks, n_metadata_blocks;

		uint64_t n_bitmap_bits;



		wc->memory_map_size -= (uint64_t)wc->start_sector << SECTOR_SHIFT;



		bio_list_init(&wc->flush_list);

		wc->flush_thread = kthread_create(writecache_flush_thread, wc, "dm_writecache_flush");

		if (IS_ERR(wc->flush_thread)) {
@@ -2097,7 +2112,7 @@ invalid_optional: 
		}



		region.bdev = wc->ssd_dev->bdev;

		region.sector = 0;

		region.sector = wc->start_sector;

		region.count = wc->metadata_sectors;

		req.bi_op = REQ_OP_READ;

		req.bi_op_flags = REQ_SYNC;
@@ -2265,7 +2280,7 @@ static void writecache_status(struct dm_target *ti, status_type_t type, 


static struct target_type writecache_target = {

	.name			= "writecache",

	.version		= {1, 0, 0},

	.version		= {1, 1, 0},

	.module			= THIS_MODULE,

	.ctr			= writecache_ctr,

	.dtr			= writecache_dtr,

CRA Git | Maintained and supported by SUSTech CRA and CCSE