Lines Matching refs:block
9 The layout of a standard block group is approximately as follows (each
25 - 1 block
28 - 1 block
29 - 1 block
33 For the special case of block group 0, the first 1024 bytes are unused,
35 The superblock will start at offset 1024 bytes, whichever block that
36 happens to be (usually 0). However, if for some reason the block size =
37 1024, then block 0 is marked in use and the superblock goes in block 1.
38 For all other block groups, there is no padding.
41 descriptors that are found in block group 0. Redundant copies of the
42 superblock and group descriptors are written to some of the block groups
44 not all block groups necessarily host a redundant copy (see following
46 copy, the block group begins with the data block bitmap. Note also that
48 GDT block” space after the block group descriptors and before the start
49 of the block bitmaps to allow for future expansion of the filesystem. By
57 As for the ordering of items in a block group, it is generally
58 established that the super block and the group descriptor table, if
59 present, will be at the beginning of the block group. The bitmaps and
63 block maps, extent tree blocks, and extended attributes.
68 Starting in ext4, there is a new feature called flexible block groups
69 (flex_bg). In a flex_bg, several block groups are tied together as one
70 logical block group; the bitmap spaces and the inode table space in the
71 first block group of the flex_bg are expanded to include the bitmaps
72 and inode tables of all other block groups in the flex_bg. For example,
74 superblock, group descriptors, data block bitmaps for groups 0-3, inode
77 block group metadata close together for faster loading, and to enable
79 and group descriptors are always at the beginning of block groups, even
80 if flex_bg is enabled. The number of block groups that make up a
86 Without the option META_BG, for safety concerns, all block group
87 descriptors copies are kept in the first block group. Given the default
88 128MiB(2^27 bytes) block group size and 64-byte group descriptors, ext4
89 can have at most 2^27/64 = 2^21 block groups. This limits the entire
95 groups. Each metablock group is a cluster of block groups whose group
96 descriptor structures can be stored in a single disk block. For ext4
97 filesystems with 4 KB block size, a single metablock group partition
98 includes 64 block groups, or 8 GiB of disk space. The metablock group
100 first block group of the whole filesystem into the first group of each
102 each metablock group. This increases the 2^21 maximum block groups limit
106 the superblock is followed by a variable-length set of block group
107 descriptors. Instead, the superblock and a single block group descriptor
108 block is placed at the beginning of the first, second, and last block
109 groups in a meta-block group. A meta-block group is a collection of
110 block groups which can be described by a single block group descriptor
111 block. Since the size of the block group descriptor structure is 64
112 bytes, a meta-block group contains 16 block groups for filesystems with
113 a 1KB block size, and 64 block groups for filesystems with a 4KB
114 blocksize. Filesystems can either be created using this new block group
117 block group using this new layout.
120 block and inode bitmaps.
125 A new feature for ext4 are three block group descriptor flags that
126 enable mkfs to skip initializing other parts of the block group
128 that the inode and block bitmaps for that group can be calculated and
130 generally the case for an empty block group or a block group containing
131 only fixed-location block group metadata. The INODE_ZEROED flag means