dm thin: allow metadata space larger than supported to go unused
It was always intended that a user could provide a thin metadata device
that is larger than the max supported by the on-disk format. The extra
space would just go unused.
Unfortunately that never worked. If the user attempted to use a larger
metadata device on creation they would get an error like the following:
device-mapper: space map common: space map too large
device-mapper: transaction manager: couldn't create metadata space map
device-mapper: thin metadata: tm_create_with_sm failed
device-mapper: table: 252:17: thin-pool: Error creating metadata object
device-mapper: ioctl: error adding target to table
Fix this by allowing the initial metadata space map creation to cap its
size at the max number of blocks supported (DM_SM_METADATA_MAX_BLOCKS).
get_metadata_dev_size() must also impose DM_SM_METADATA_MAX_BLOCKS (via
THIN_METADATA_MAX_SECTORS), otherwise extending metadata would cap at
THIN_METADATA_MAX_SECTORS_WARNING (which is larger than supported).
Also, the calculation for THIN_METADATA_MAX_SECTORS didn't account for
the sizeof the disk_bitmap_header. So the supported maximum metadata
size is a bit smaller (reduced from 33423360 to 33292800 sectors).
Lastly, remove the "excess space will not be used" warning message from
get_metadata_dev_size(); it resulted in printing the warning multiple
times. Factor out warn_if_metadata_device_too_big(), call it from
pool_ctr() and maybe_resize_metadata_dev().
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Joe Thornber <ejt@redhat.com>
diff --git a/drivers/md/persistent-data/dm-space-map-metadata.h b/drivers/md/persistent-data/dm-space-map-metadata.h
index 39bba08..64df923 100644
--- a/drivers/md/persistent-data/dm-space-map-metadata.h
+++ b/drivers/md/persistent-data/dm-space-map-metadata.h
@@ -9,6 +9,17 @@
#include "dm-transaction-manager.h"
+#define DM_SM_METADATA_BLOCK_SIZE (4096 >> SECTOR_SHIFT)
+
+/*
+ * The metadata device is currently limited in size.
+ *
+ * We have one block of index, which can hold 255 index entries. Each
+ * index entry contains allocation info about ~16k metadata blocks.
+ */
+#define DM_SM_METADATA_MAX_BLOCKS (255 * ((1 << 14) - 64))
+#define DM_SM_METADATA_MAX_SECTORS (DM_SM_METADATA_MAX_BLOCKS * DM_SM_METADATA_BLOCK_SIZE)
+
/*
* Unfortunately we have to use two-phase construction due to the cycle
* between the tm and sm.