From: Mike Snitzer Permit a target to support discards regardless of whether or not all its underlying devices do. Signed-off-by: Mike Snitzer Signed-off-by: Alasdair G Kergon --- drivers/md/dm-table.c | 6 +++++- include/linux/device-mapper.h | 6 ++++++ 2 files changed, 11 insertions(+), 1 deletion(-) Index: linux-2.6.39/drivers/md/dm-table.c =================================================================== --- linux-2.6.39.orig/drivers/md/dm-table.c +++ linux-2.6.39/drivers/md/dm-table.c @@ -1346,7 +1346,8 @@ bool dm_table_supports_discards(struct d return 0; /* - * Ensure that at least one underlying device supports discards. + * Unless any target used by the table set discards_supported, + * require at least one underlying device to support discards. * t->devices includes internal dm devices such as mirror logs * so we need to use iterate_devices here, which targets * supporting discard must provide. @@ -1354,6 +1355,9 @@ bool dm_table_supports_discards(struct d while (i < dm_table_get_num_targets(t)) { ti = dm_table_get_target(t, i++); + if (ti->discards_supported) + return 1; + if (ti->type->iterate_devices && ti->type->iterate_devices(ti, device_discard_capable, NULL)) return 1; Index: linux-2.6.39/include/linux/device-mapper.h =================================================================== --- linux-2.6.39.orig/include/linux/device-mapper.h +++ linux-2.6.39/include/linux/device-mapper.h @@ -191,6 +191,12 @@ struct dm_target { /* Used to provide an error string from the ctr */ char *error; + + /* + * Set if this target needs to receive discards regardless of + * whether or not its underlying devices have support. + */ + unsigned discards_supported:1; }; /* Each target can link one of these into the table */