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-rw-r--r--fs/hfsplus/btree.c112
1 files changed, 112 insertions, 0 deletions
diff --git a/fs/hfsplus/btree.c b/fs/hfsplus/btree.c
index 0c6540c91167..0fcec8b2a90b 100644
--- a/fs/hfsplus/btree.c
+++ b/fs/hfsplus/btree.c
@@ -15,6 +15,118 @@
#include "hfsplus_fs.h"
#include "hfsplus_raw.h"
+/*
+ * Initial source code of clump size calculation is gotten
+ * from http://opensource.apple.com/tarballs/diskdev_cmds/
+ */
+#define CLUMP_ENTRIES 15
+
+static short clumptbl[CLUMP_ENTRIES * 3] = {
+/*
+ * Volume Attributes Catalog Extents
+ * Size Clump (MB) Clump (MB) Clump (MB)
+ */
+ /* 1GB */ 4, 4, 4,
+ /* 2GB */ 6, 6, 4,
+ /* 4GB */ 8, 8, 4,
+ /* 8GB */ 11, 11, 5,
+ /*
+ * For volumes 16GB and larger, we want to make sure that a full OS
+ * install won't require fragmentation of the Catalog or Attributes
+ * B-trees. We do this by making the clump sizes sufficiently large,
+ * and by leaving a gap after the B-trees for them to grow into.
+ *
+ * For SnowLeopard 10A298, a FullNetInstall with all packages selected
+ * results in:
+ * Catalog B-tree Header
+ * nodeSize: 8192
+ * totalNodes: 31616
+ * freeNodes: 1978
+ * (used = 231.55 MB)
+ * Attributes B-tree Header
+ * nodeSize: 8192
+ * totalNodes: 63232
+ * freeNodes: 958
+ * (used = 486.52 MB)
+ *
+ * We also want Time Machine backup volumes to have a sufficiently
+ * large clump size to reduce fragmentation.
+ *
+ * The series of numbers for Catalog and Attribute form a geometric
+ * series. For Catalog (16GB to 512GB), each term is 8**(1/5) times
+ * the previous term. For Attributes (16GB to 512GB), each term is
+ * 4**(1/5) times the previous term. For 1TB to 16TB, each term is
+ * 2**(1/5) times the previous term.
+ */
+ /* 16GB */ 64, 32, 5,
+ /* 32GB */ 84, 49, 6,
+ /* 64GB */ 111, 74, 7,
+ /* 128GB */ 147, 111, 8,
+ /* 256GB */ 194, 169, 9,
+ /* 512GB */ 256, 256, 11,
+ /* 1TB */ 294, 294, 14,
+ /* 2TB */ 338, 338, 16,
+ /* 4TB */ 388, 388, 20,
+ /* 8TB */ 446, 446, 25,
+ /* 16TB */ 512, 512, 32
+};
+
+u32 hfsplus_calc_btree_clump_size(u32 block_size, u32 node_size,
+ u64 sectors, int file_id)
+{
+ u32 mod = max(node_size, block_size);
+ u32 clump_size;
+ int column;
+ int i;
+
+ /* Figure out which column of the above table to use for this file. */
+ switch (file_id) {
+ case HFSPLUS_ATTR_CNID:
+ column = 0;
+ break;
+ case HFSPLUS_CAT_CNID:
+ column = 1;
+ break;
+ default:
+ column = 2;
+ break;
+ }
+
+ /*
+ * The default clump size is 0.8% of the volume size. And
+ * it must also be a multiple of the node and block size.
+ */
+ if (sectors < 0x200000) {
+ clump_size = sectors << 2; /* 0.8 % */
+ if (clump_size < (8 * node_size))
+ clump_size = 8 * node_size;
+ } else {
+ /* turn exponent into table index... */
+ for (i = 0, sectors = sectors >> 22;
+ sectors && (i < CLUMP_ENTRIES - 1);
+ ++i, sectors = sectors >> 1) {
+ /* empty body */
+ }
+
+ clump_size = clumptbl[column + (i) * 3] * 1024 * 1024;
+ }
+
+ /*
+ * Round the clump size to a multiple of node and block size.
+ * NOTE: This rounds down.
+ */
+ clump_size /= mod;
+ clump_size *= mod;
+
+ /*
+ * Rounding down could have rounded down to 0 if the block size was
+ * greater than the clump size. If so, just use one block or node.
+ */
+ if (clump_size == 0)
+ clump_size = mod;
+
+ return clump_size;
+}
/* Get a reference to a B*Tree and do some initial checks */
struct hfs_btree *hfs_btree_open(struct super_block *sb, u32 id)