Lines Matching +full:i +full:- +full:cache +full:- +full:block +full:- +full:size
4 EROFS file-system stands for Enhanced Read-Only File System. Different
5 from other read-only file systems, it aims to be designed for flexibility,
9 - read-only storage media or
11 - part of a fully trusted read-only solution, which means it needs to be
12 immutable and bit-for-bit identical to the official golden image for
15 - hope to save some extra storage space with guaranteed end-to-end performance
20 - Little endian on-disk design;
22 - Currently 4KB block size (nobh) and therefore maximum 16TB address space;
24 - Metadata & data could be mixed by design;
26 - 2 inode versions for different requirements:
28 Inode metadata size: 32 bytes 64 bytes
29 Max file size: 4 GB 16 EB (also limited by max. vol size)
31 File creation time: no yes (64 + 32-bit timestamp)
35 - Support extended attributes (xattrs) as an option;
37 - Support xattr inline and tail-end data inline for all files;
39 - Support POSIX.1e ACLs by using xattrs;
41 - Support transparent file compression as an option:
42 LZ4 algorithm with 4 KB fixed-output compression for high performance;
44 The following git tree provides the file system user-space tools under
46 >> git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs-utils.git
49 linux-erofs mailing list:
50 >> linux-erofs mailing list <linux-erofs@lists.ozlabs.org>
60 disabled: In-place I/O decompression only;
61 readahead: Cache the last incomplete compressed physical
63 in-place I/O decompression for the rest
65 readaround: Cache the both ends of incomplete compressed
67 It still does in-place I/O decompression
70 On-disk details
74 -------
75 Different from other read-only file systems, an EROFS volume is designed
78 |-> aligned with the block size
84 All data areas should be aligned with the block size, but metadata areas
88 value (32 bytes) and designed to be kept in line with v1 inode size.
93 |-> aligned with 8B
94 |-> followed closely
95 + meta_blkaddr blocks |-> another slot
99 |-> aligned with the inode slot size
106 .____________________________________________________|-> aligned with 4B
109 |-> 12 bytes <-|->x * 4 bytes<-| .
116 |-> aligned with 4B
117 |-> aligned with 4B
120 field which all inode versions have -- i_advise:
136 2) fixed-output size data compression (must have extents);
137 3) flat file data with tail-end data inline (no extent);
139 The size of the optional xattrs is indicated by i_xattr_count in inode
145 a specific block indicated by xattr_blkaddr, organized one by one with
151 |-> aligned by 4 bytes
152 + xattr_blkaddr blocks |-> aligned with 4 bytes
158 -----------
159 All directories are now organized in a compact on-disk format. Note that
160 each directory block is divided into index and name areas in order to support
168 / / | nameoff1 | nameoffN-1
171 |___.0___|____1___|_____|___N-1__|____0_____|____1_____|_____|___N-1____|
177 Directory block
180 the total number of directory entries in this block since it is no need to
181 introduce another on-disk field at all.
184 -----------
185 Currently, EROFS supports 4KB fixed-output clustersize transparent file
188 |---- Variant-Length Extent ----|-------- VLE --------|----- VLE -----
194 |-> cluster <-|-> cluster <-|-> cluster <-|-> cluster <-|-> cluster <-|
195 size size size size size
202 |-> cluster <-|-> cluster <-|-> cluster <-|
203 size size size
205 Currently each on-disk physical cluster can contain 4KB (un)compressed data
206 at most. For each logical cluster, there is a corresponding on-disk index to