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Diffstat (limited to 'fs/hfsplus/btree.c')
| -rw-r--r-- | fs/hfsplus/btree.c | 112 |
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) |
