Messages in this thread Patch in this message | | | Date | Mon, 28 Feb 2011 23:38:45 +0000 | From | Phillip Lougher <> | Subject | [PATCH 4/6] Squashfs: Update documentation to include compression options |
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Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk> --- Documentation/filesystems/squashfs.txt | 28 +++++++++++++++++++--------- 1 files changed, 19 insertions(+), 9 deletions(-)
diff --git a/Documentation/filesystems/squashfs.txt b/Documentation/filesystems/squashfs.txt index 66699af..2d78f19 100644 --- a/Documentation/filesystems/squashfs.txt +++ b/Documentation/filesystems/squashfs.txt @@ -59,12 +59,15 @@ obtained from this site also. 3. SQUASHFS FILESYSTEM DESIGN -----------------------------
-A squashfs filesystem consists of a maximum of eight parts, packed together on a byte -alignment: +A squashfs filesystem consists of a maximum of nine parts, packed together on a +byte alignment:
--------------- | superblock | |---------------| + | compression | + | options | + |---------------| | datablocks | | & fragments | |---------------| @@ -91,7 +94,14 @@ the source directory, and checked for duplicates. Once all file data has been written the completed inode, directory, fragment, export and uid/gid lookup tables are written.
-3.1 Inodes +3.1 Compression options +----------------------- + +Compressors can optionally support compression specific options (e.g. +dictionary size). If non-default compression options have been used, then +these are stored here. + +3.2 Inodes ----------
Metadata (inodes and directories) are compressed in 8Kbyte blocks. Each @@ -114,7 +124,7 @@ directory inode are defined: inodes optimised for frequently occurring regular files and directories, and extended types where extra information has to be stored.
-3.2 Directories +3.3 Directories ---------------
Like inodes, directories are packed into compressed metadata blocks, stored @@ -144,7 +154,7 @@ decompressed to do a lookup irrespective of the length of the directory. This scheme has the advantage that it doesn't require extra memory overhead and doesn't require much extra storage on disk.
-3.3 File data +3.4 File data -------------
Regular files consist of a sequence of contiguous compressed blocks, and/or a @@ -163,7 +173,7 @@ Larger files use multiple slots, with 1.75 TiB files using all 8 slots. The index cache is designed to be memory efficient, and by default uses 16 KiB.
-3.4 Fragment lookup table +3.5 Fragment lookup table -------------------------
Regular files can contain a fragment index which is mapped to a fragment @@ -173,7 +183,7 @@ A second index table is used to locate these. This second index table for speed of access (and because it is small) is read at mount time and cached in memory.
-3.5 Uid/gid lookup table +3.6 Uid/gid lookup table ------------------------
For space efficiency regular files store uid and gid indexes, which are @@ -182,7 +192,7 @@ stored compressed into metadata blocks. A second index table is used to locate these. This second index table for speed of access (and because it is small) is read at mount time and cached in memory.
-3.6 Export table +3.7 Export table ----------------
To enable Squashfs filesystems to be exportable (via NFS etc.) filesystems @@ -196,7 +206,7 @@ This table is stored compressed into metadata blocks. A second index table is used to locate these. This second index table for speed of access (and because it is small) is read at mount time and cached in memory.
-3.7 Xattr table +3.8 Xattr table ---------------
The xattr table contains extended attributes for each inode. The xattrs -- 1.7.1
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