dm snapshot: fix on disk chunk size validation
Fix some problems seen in the chunk size processing when activating a
pre-existing snapshot.
For a new snapshot, the chunk size can either be supplied by the creator
or a default value can be used. For an existing snapshot, the
chunk size in the snapshot header on disk should always be used.
If someone attempts to load an existing snapshot and has the 'default
chunk size' option set, the kernel uses its default value even when it
is incorrect for the snapshot being loaded. This patch ensures the
correct on-disk value is always used.
Secondly, when the code does use the chunk size stored on the disk it is
prudent to revalidate it, so the code can exit cleanly if it got
corrupted as happened in
https://bugzilla.redhat.com/show_bug.cgi?id=461506 .
Cc: stable@kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
diff --git a/drivers/md/dm-snap-persistent.c b/drivers/md/dm-snap-persistent.c
index 5d1a975..d5b2e087 100644
--- a/drivers/md/dm-snap-persistent.c
+++ b/drivers/md/dm-snap-persistent.c
@@ -286,6 +286,7 @@
struct disk_header *dh;
chunk_t chunk_size;
int chunk_size_supplied = 1;
+ char *chunk_err;
/*
* Use default chunk size (or hardsect_size, if larger) if none supplied
@@ -329,20 +330,25 @@
ps->version = le32_to_cpu(dh->version);
chunk_size = le32_to_cpu(dh->chunk_size);
- if (!chunk_size_supplied || ps->store->chunk_size == chunk_size)
+ if (ps->store->chunk_size == chunk_size)
return 0;
- DMWARN("chunk size %llu in device metadata overrides "
- "table chunk size of %llu.",
- (unsigned long long)chunk_size,
- (unsigned long long)ps->store->chunk_size);
+ if (chunk_size_supplied)
+ DMWARN("chunk size %llu in device metadata overrides "
+ "table chunk size of %llu.",
+ (unsigned long long)chunk_size,
+ (unsigned long long)ps->store->chunk_size);
/* We had a bogus chunk_size. Fix stuff up. */
free_area(ps);
- ps->store->chunk_size = chunk_size;
- ps->store->chunk_mask = chunk_size - 1;
- ps->store->chunk_shift = ffs(chunk_size) - 1;
+ r = dm_exception_store_set_chunk_size(ps->store, chunk_size,
+ &chunk_err);
+ if (r) {
+ DMERR("invalid on-disk chunk size %llu: %s.",
+ (unsigned long long)chunk_size, chunk_err);
+ return r;
+ }
r = dm_io_client_resize(sectors_to_pages(ps->store->chunk_size),
ps->io_client);
