bcache: Make sure blocksize isn't smaller than device blocksize

Sanity check to make sure we don't end up doing IO the device doesn't
support.

Signed-off-by: Kent Overstreet <koverstreet@google.com>

diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 6817ea4..b360147 100644 (file)
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -139,13 +139,17 @@ static const char *read_super(struct cache_sb *sb, struct block_device *bdev,
        if (bch_is_zero(sb->uuid, 16))
                goto err;
 
+       sb->block_size  = le16_to_cpu(s->block_size);
+
+       err = "Superblock block size smaller than device block size";
+       if (sb->block_size << 9 < bdev_logical_block_size(bdev))
+               goto err;
+
        switch (sb->version) {
        case BCACHE_SB_VERSION_BDEV:
-               sb->block_size  = le16_to_cpu(s->block_size);
                sb->data_offset = BDEV_DATA_START_DEFAULT;
                break;
        case BCACHE_SB_VERSION_BDEV_WITH_OFFSET:
-               sb->block_size  = le16_to_cpu(s->block_size);
                sb->data_offset = le64_to_cpu(s->data_offset);
 
                err = "Bad data offset";