Select suitable cluster size when creating a huge FS (128 TB or more).

git-svn-id: http://exfat.googlecode.com/svn/trunk@278 60bc1c72-a15a-11de-b98f-4500b42dc123

diff --git a/libexfat/exfat.h b/libexfat/exfat.h
index a5a9ba1..2a831a3 100644 (file)
--- a/libexfat/exfat.h
+++ b/libexfat/exfat.h
@@ -41,6 +41,7 @@
 #define CLUSTER_INVALID(c) ((c) > EXFAT_LAST_DATA_CLUSTER)
 
 #define MIN(a, b) ((a) < (b) ? (a) : (b))
+#define MAX(a, b) ((a) > (b) ? (a) : (b))
 #define DIV_ROUND_UP(x, d) (((x) + (d) - 1) / (d))
 
 #define BMAP_GET(bitmap, index) \

diff --git a/mkfs/main.c b/mkfs/main.c
index 675140a..1f78b44 100644 (file)
--- a/mkfs/main.c
+++ b/mkfs/main.c
@@ -247,17 +247,21 @@ static int write_structures(struct exfat_dev* dev)
        return 0;
 }
 
-static int get_spc_bits(int user_defined, off_t volume_size)
+static int get_spc_bits(int sector_bits, int user_defined, off_t volume_size)
 {
+       int i;
+
        if (user_defined != -1)
                return user_defined;
 
        if (volume_size < 256ull * 1024 * 1024)
-               return 3;       /* 4 KB */
-       else if (volume_size < 32ull * 1024 * 1024 * 1024)
-               return 6;       /* 32 KB */
-       else
-               return 8;       /* 128 KB */
+               return MAX(0, 12 - sector_bits);        /* 4 KB */
+       if (volume_size < 32ull * 1024 * 1024 * 1024)
+               return MAX(0, 15 - sector_bits);        /* 32 KB */
+
+       for (i = 17; ; i++)                                             /* 128 KB or more */
+               if (DIV_ROUND_UP(volume_size, 1 << i) <= EXFAT_LAST_DATA_CLUSTER)
+                       return MAX(0, i - sector_bits);
 }
 
 static int set_volume_label(const char* volume_label)
@@ -306,7 +310,7 @@ static int mkfs(const char* spec, int sector_bits, int spc_bits,
                exfat_error("seek failed");
                return 1;
        }
-       spc_bits = get_spc_bits(spc_bits, volume_size);
+       spc_bits = get_spc_bits(sector_bits, spc_bits, volume_size);
 
        if (set_volume_label(volume_label) != 0)
        {