diff options
Diffstat (limited to 'Documentation/filesystems')
| -rw-r--r-- | Documentation/filesystems/erofs.txt | 27 | ||||
| -rw-r--r-- | Documentation/filesystems/overlayfs.rst (renamed from Documentation/filesystems/overlayfs.txt) | 10 |
2 files changed, 20 insertions, 17 deletions
diff --git a/Documentation/filesystems/erofs.txt b/Documentation/filesystems/erofs.txt index b0c085326e2e..db6d39c3ae71 100644 --- a/Documentation/filesystems/erofs.txt +++ b/Documentation/filesystems/erofs.txt @@ -24,11 +24,11 @@ Here is the main features of EROFS: - Metadata & data could be mixed by design; - 2 inode versions for different requirements: - v1 v2 + compact (v1) extended (v2) Inode metadata size: 32 bytes 64 bytes Max file size: 4 GB 16 EB (also limited by max. vol size) Max uids/gids: 65536 4294967296 - File creation time: no yes (64 + 32-bit timestamp) + File change time: no yes (64 + 32-bit timestamp) Max hardlinks: 65536 4294967296 Metadata reserved: 4 bytes 14 bytes @@ -39,7 +39,7 @@ Here is the main features of EROFS: - Support POSIX.1e ACLs by using xattrs; - Support transparent file compression as an option: - LZ4 algorithm with 4 KB fixed-output compression for high performance; + LZ4 algorithm with 4 KB fixed-sized output compression for high performance. The following git tree provides the file system user-space tools under development (ex, formatting tool mkfs.erofs): @@ -85,7 +85,7 @@ All data areas should be aligned with the block size, but metadata areas may not. All metadatas can be now observed in two different spaces (views): 1. Inode metadata space Each valid inode should be aligned with an inode slot, which is a fixed - value (32 bytes) and designed to be kept in line with v1 inode size. + value (32 bytes) and designed to be kept in line with compact inode size. Each inode can be directly found with the following formula: inode offset = meta_blkaddr * block_size + 32 * nid @@ -117,10 +117,10 @@ may not. All metadatas can be now observed in two different spaces (views): |-> aligned with 4B Inode could be 32 or 64 bytes, which can be distinguished from a common - field which all inode versions have -- i_advise: + field which all inode versions have -- i_format: __________________ __________________ - | i_advise | | i_advise | + | i_format | | i_format | |__________________| |__________________| | ... | | ... | | | | | @@ -129,12 +129,13 @@ may not. All metadatas can be now observed in two different spaces (views): |__________________| 64 bytes Xattrs, extents, data inline are followed by the corresponding inode with - proper alignes, and they could be optional for different data mappings, - _currently_ there are totally 3 valid data mappings supported: + proper alignment, and they could be optional for different data mappings. + _currently_ total 4 valid data mappings are supported: - 1) flat file data without data inline (no extent); - 2) fixed-output size data compression (must have extents); - 3) flat file data with tail-end data inline (no extent); + 0 flat file data without data inline (no extent); + 1 fixed-sized output data compression (with non-compacted indexes); + 2 flat file data with tail packing data inline (no extent); + 3 fixed-sized output data compression (with compacted indexes, v5.3+). The size of the optional xattrs is indicated by i_xattr_count in inode header. Large xattrs or xattrs shared by many different files can be @@ -182,8 +183,8 @@ introduce another on-disk field at all. Compression ----------- -Currently, EROFS supports 4KB fixed-output clustersize transparent file -compression, as illustrated below: +Currently, EROFS supports 4KB fixed-sized output transparent file compression, +as illustrated below: |---- Variant-Length Extent ----|-------- VLE --------|----- VLE ----- clusterofs clusterofs clusterofs diff --git a/Documentation/filesystems/overlayfs.txt b/Documentation/filesystems/overlayfs.rst index 845d689e0fd7..e443be7928db 100644 --- a/Documentation/filesystems/overlayfs.txt +++ b/Documentation/filesystems/overlayfs.rst @@ -1,3 +1,5 @@ +.. SPDX-License-Identifier: GPL-2.0 + Written by: Neil Brown Please see MAINTAINERS file for where to send questions. @@ -181,7 +183,7 @@ Kernel config options: worried about backward compatibility with kernels that have the redirect_dir feature and follow redirects even if turned off. -Module options (can also be changed through /sys/module/overlay/parameters/*): +Module options (can also be changed through /sys/module/overlay/parameters/): - "redirect_dir=BOOL": See OVERLAY_FS_REDIRECT_DIR kernel config option above. @@ -263,7 +265,7 @@ top, lower2 the middle and lower3 the bottom layer. Metadata only copy up --------------------- +--------------------- When metadata only copy up feature is enabled, overlayfs will only copy up metadata (as opposed to whole file), when a metadata specific operation @@ -286,10 +288,10 @@ pointed by REDIRECT. This should not be possible on local system as setting "trusted." xattrs will require CAP_SYS_ADMIN. But it should be possible for untrusted layers like from a pen drive. -Note: redirect_dir={off|nofollow|follow(*)} conflicts with metacopy=on, and +Note: redirect_dir={off|nofollow|follow[*]} conflicts with metacopy=on, and results in an error. -(*) redirect_dir=follow only conflicts with metacopy=on if upperdir=... is +[*] redirect_dir=follow only conflicts with metacopy=on if upperdir=... is given. Sharing and copying layers |