dm snapshot: add new persistent store option to support overflow
Commit 76c44f6d80 introduced the possibly for "Overflow" to be reported
by the snapshot device's status. Older userspace (e.g. lvm2) does not
handle the "Overflow" status response.
Fix this incompatibility by requiring newer userspace code, that can
cope with "Overflow", request the persistent store with overflow support
by using "PO" (Persistent with Overflow) for the snapshot store type.
Reported-by: Zdenek Kabelac <zkabelac@redhat.com>
Fixes: 76c44f6d80 ("dm snapshot: don't invalidate on-disk image on snapshot write overflow")
Reviewed-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
diff --git a/drivers/md/dm-snap-persistent.c b/drivers/md/dm-snap-persistent.c
index bf71583..aeacad9 100644
--- a/drivers/md/dm-snap-persistent.c
+++ b/drivers/md/dm-snap-persistent.c
@@ -7,6 +7,7 @@
#include "dm-exception-store.h"
+#include <linux/ctype.h>
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/vmalloc.h>
@@ -843,8 +844,7 @@
DMWARN("write header failed");
}
-static int persistent_ctr(struct dm_exception_store *store,
- unsigned argc, char **argv)
+static int persistent_ctr(struct dm_exception_store *store, char *options)
{
struct pstore *ps;
@@ -873,6 +873,16 @@
return -ENOMEM;
}
+ if (options) {
+ char overflow = toupper(options[0]);
+ if (overflow == 'O')
+ store->userspace_supports_overflow = true;
+ else {
+ DMERR("Unsupported persistent store option: %s", options);
+ return -EINVAL;
+ }
+ }
+
store->context = ps;
return 0;
@@ -888,7 +898,8 @@
case STATUSTYPE_INFO:
break;
case STATUSTYPE_TABLE:
- DMEMIT(" P %llu", (unsigned long long)store->chunk_size);
+ DMEMIT(" %s %llu", store->userspace_supports_overflow ? "PO" : "P",
+ (unsigned long long)store->chunk_size);
}
return sz;