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-rw-r--r--Documentation/filesystems/ext4/blockgroup.rst30
1 files changed, 15 insertions, 15 deletions
diff --git a/Documentation/filesystems/ext4/blockgroup.rst b/Documentation/filesystems/ext4/blockgroup.rst
index d5d652addce5..46d78f860623 100644
--- a/Documentation/filesystems/ext4/blockgroup.rst
+++ b/Documentation/filesystems/ext4/blockgroup.rst
@@ -56,39 +56,39 @@ established that the super block and the group descriptor table, if
present, will be at the beginning of the block group. The bitmaps and
the inode table can be anywhere, and it is quite possible for the
bitmaps to come after the inode table, or for both to be in different
-groups (flex\_bg). Leftover space is used for file data blocks, indirect
+groups (flex_bg). Leftover space is used for file data blocks, indirect
block maps, extent tree blocks, and extended attributes.
Flexible Block Groups
---------------------
Starting in ext4, there is a new feature called flexible block groups
-(flex\_bg). In a flex\_bg, several block groups are tied together as one
+(flex_bg). In a flex_bg, several block groups are tied together as one
logical block group; the bitmap spaces and the inode table space in the
-first block group of the flex\_bg are expanded to include the bitmaps
-and inode tables of all other block groups in the flex\_bg. For example,
-if the flex\_bg size is 4, then group 0 will contain (in order) the
+first block group of the flex_bg are expanded to include the bitmaps
+and inode tables of all other block groups in the flex_bg. For example,
+if the flex_bg size is 4, then group 0 will contain (in order) the
superblock, group descriptors, data block bitmaps for groups 0-3, inode
bitmaps for groups 0-3, inode tables for groups 0-3, and the remaining
space in group 0 is for file data. The effect of this is to group the
block group metadata close together for faster loading, and to enable
large files to be continuous on disk. Backup copies of the superblock
and group descriptors are always at the beginning of block groups, even
-if flex\_bg is enabled. The number of block groups that make up a
-flex\_bg is given by 2 ^ ``sb.s_log_groups_per_flex``.
+if flex_bg is enabled. The number of block groups that make up a
+flex_bg is given by 2 ^ ``sb.s_log_groups_per_flex``.
Meta Block Groups
-----------------
-Without the option META\_BG, for safety concerns, all block group
+Without the option META_BG, for safety concerns, all block group
descriptors copies are kept in the first block group. Given the default
128MiB(2^27 bytes) block group size and 64-byte group descriptors, ext4
can have at most 2^27/64 = 2^21 block groups. This limits the entire
filesystem size to 2^21 * 2^27 = 2^48bytes or 256TiB.
The solution to this problem is to use the metablock group feature
-(META\_BG), which is already in ext3 for all 2.6 releases. With the
-META\_BG feature, ext4 filesystems are partitioned into many metablock
+(META_BG), which is already in ext3 for all 2.6 releases. With the
+META_BG feature, ext4 filesystems are partitioned into many metablock
groups. Each metablock group is a cluster of block groups whose group
descriptor structures can be stored in a single disk block. For ext4
filesystems with 4 KB block size, a single metablock group partition
@@ -110,7 +110,7 @@ bytes, a meta-block group contains 32 block groups for filesystems with
a 1KB block size, and 128 block groups for filesystems with a 4KB
blocksize. Filesystems can either be created using this new block group
descriptor layout, or existing filesystems can be resized on-line, and
-the field s\_first\_meta\_bg in the superblock will indicate the first
+the field s_first_meta_bg in the superblock will indicate the first
block group using this new layout.
Please see an important note about ``BLOCK_UNINIT`` in the section about
@@ -121,15 +121,15 @@ Lazy Block Group Initialization
A new feature for ext4 are three block group descriptor flags that
enable mkfs to skip initializing other parts of the block group
-metadata. Specifically, the INODE\_UNINIT and BLOCK\_UNINIT flags mean
+metadata. Specifically, the INODE_UNINIT and BLOCK_UNINIT flags mean
that the inode and block bitmaps for that group can be calculated and
therefore the on-disk bitmap blocks are not initialized. This is
generally the case for an empty block group or a block group containing
-only fixed-location block group metadata. The INODE\_ZEROED flag means
+only fixed-location block group metadata. The INODE_ZEROED flag means
that the inode table has been initialized; mkfs will unset this flag and
rely on the kernel to initialize the inode tables in the background.
By not writing zeroes to the bitmaps and inode table, mkfs time is
-reduced considerably. Note the feature flag is RO\_COMPAT\_GDT\_CSUM,
-but the dumpe2fs output prints this as “uninit\_bg”. They are the same
+reduced considerably. Note the feature flag is RO_COMPAT_GDT_CSUM,
+but the dumpe2fs output prints this as “uninit_bg”. They are the same
thing.