dm cache: add data block size limits to code and Documentation

Place upper bound on the cache's data block size (1GB).

Inform users that the data block size can't be any arbitrary number,
i.e. its value must be between 32KB and 1GB.  Also, it should be a
multiple of 32KB.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Acked-by: Joe Thornber <ejt@redhat.com>

diff --git a/Documentation/device-mapper/cache.txt b/Documentation/device-mapper/cache.txt
index af99c458c841dd248b443ad0ac74cacc8657614e..33d45ee0b737fade096136d50425caf46e344a47 100644 (file)
--- a/Documentation/device-mapper/cache.txt
+++ b/Documentation/device-mapper/cache.txt
@@ -58,7 +58,8 @@ Fixed block size
 
 The origin is divided up into blocks of a fixed size.  This block size
 is configurable when you first create the cache.  Typically we've been
-using block sizes of 256k - 1024k.
+using block sizes of 256KB - 1024KB.  The block size must be between 64
+(32KB) and 2097152 (1GB) and a multiple of 64 (32KB).
 
 Having a fixed block size simplifies the target a lot.  But it is
 something of a compromise.  For instance, a small part of a block may be

diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
index 0df3ec085ebb49705c4db91815eb8df90808703a..31985ea8140810cad808fdec15e3d65d4db14775 100644 (file)
--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -67,9 +67,11 @@ static void free_bitset(unsigned long *bits)
 #define MIGRATION_COUNT_WINDOW 10
 
 /*
- * The block size of the device holding cache data must be >= 32KB
+ * The block size of the device holding cache data must be
+ * between 32KB and 1GB.
  */
 #define DATA_DEV_BLOCK_SIZE_MIN_SECTORS (32 * 1024 >> SECTOR_SHIFT)
+#define DATA_DEV_BLOCK_SIZE_MAX_SECTORS (1024 * 1024 * 1024 >> SECTOR_SHIFT)
 
 /*
  * FIXME: the cache is read/write for the time being.
@@ -1687,24 +1689,25 @@ static int parse_origin_dev(struct cache_args *ca, struct dm_arg_set *as,
 static int parse_block_size(struct cache_args *ca, struct dm_arg_set *as,
                            char **error)
 {
-       unsigned long tmp;
+       unsigned long block_size;
 
        if (!at_least_one_arg(as, error))
                return -EINVAL;
 
-       if (kstrtoul(dm_shift_arg(as), 10, &tmp) || !tmp ||
-           tmp < DATA_DEV_BLOCK_SIZE_MIN_SECTORS ||
-           tmp & (DATA_DEV_BLOCK_SIZE_MIN_SECTORS - 1)) {
+       if (kstrtoul(dm_shift_arg(as), 10, &block_size) || !block_size ||
+           block_size < DATA_DEV_BLOCK_SIZE_MIN_SECTORS ||
+           block_size > DATA_DEV_BLOCK_SIZE_MAX_SECTORS ||
+           block_size & (DATA_DEV_BLOCK_SIZE_MIN_SECTORS - 1)) {
                *error = "Invalid data block size";
                return -EINVAL;
        }
 
-       if (tmp > ca->cache_sectors) {
+       if (block_size > ca->cache_sectors) {
                *error = "Data block size is larger than the cache device";
                return -EINVAL;
        }
 
-       ca->block_size = tmp;
+       ca->block_size = block_size;
 
        return 0;
 }