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authorLinus Torvalds <torvalds@linux-foundation.org>2023-05-04 14:37:53 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2023-05-04 14:37:53 -0700
commit8e15605be8baeb9e3957c268c7d6f901c327ad5c (patch)
tree4749f5607932098d690fd613be96ae5a537a0335 /Documentation
parenta1fd058b07d58c3372c1aba25dd65f1c9c9b65f1 (diff)
parent21e26d5e54ab7cfe6b488fd27d4d70956d07e03b (diff)
Merge tag '9p-6.4-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ericvh/v9fs
Pull 9p updates from Eric Van Hensbergen: "This includes a number of patches that didn't quite make the cut last merge window while we addressed some outstanding issues and review comments. It includes some new caching modes for those that only want readahead caches and reworks how we do writeback caching so we are not keeping extra references around which both causes performance problems and uses lots of additional resources on the server. It also includes a new flag to force disabling of xattrs which can also cause major performance issues, particularly if the underlying filesystem on the server doesn't support them. Finally it adds a couple of additional mount options to better support directio and enabling caches when the server doesn't support qid.version. There was one late-breaking bug report that has also been included as its own patch where I forgot to propagate an embarassing bit-logic fix to the various variations of open" * tag '9p-6.4-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ericvh/v9fs: fs/9p: Fix bit operation logic error fs/9p: Rework cache modes and add new options to Documentation fs/9p: remove writeback fid and fix per-file modes fs/9p: Add new mount modes 9p: Add additional debug flags and open modes fs/9p: allow disable of xattr support on mount fs/9p: Remove unnecessary superblock flags fs/9p: Consolidate file operations and add readahead and writeback
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/filesystems/9p.rst52
1 files changed, 39 insertions, 13 deletions
diff --git a/Documentation/filesystems/9p.rst b/Documentation/filesystems/9p.rst
index 7b5964bc8865..1b5f0cc3e4ca 100644
--- a/Documentation/filesystems/9p.rst
+++ b/Documentation/filesystems/9p.rst
@@ -78,19 +78,39 @@ Options
offering several exported file systems.
cache=mode specifies a caching policy. By default, no caches are used.
-
- none
- default no cache policy, metadata and data
- alike are synchronous.
- loose
- no attempts are made at consistency,
- intended for exclusive, read-only mounts
- fscache
- use FS-Cache for a persistent, read-only
- cache backend.
- mmap
- minimal cache that is only used for read-write
- mmap. Northing else is cached, like cache=none
+ The mode can be specified as a bitmask or by using one of the
+ prexisting common 'shortcuts'.
+ The bitmask is described below: (unspecified bits are reserved)
+
+ ========== ====================================================
+ 0b00000000 all caches disabled, mmap disabled
+ 0b00000001 file caches enabled
+ 0b00000010 meta-data caches enabled
+ 0b00000100 writeback behavior (as opposed to writethrough)
+ 0b00001000 loose caches (no explicit consistency with server)
+ 0b10000000 fscache enabled for persistent caching
+ ========== ====================================================
+
+ The current shortcuts and their associated bitmask are:
+
+ ========= ====================================================
+ none 0b00000000 (no caching)
+ readahead 0b00000001 (only read-ahead file caching)
+ mmap 0b00000101 (read-ahead + writeback file cache)
+ loose 0b00001111 (non-coherent file and meta-data caches)
+ fscache 0b10001111 (persistent loose cache)
+ ========= ====================================================
+
+ NOTE: only these shortcuts are tested modes of operation at the
+ moment, so using other combinations of bit-patterns is not
+ known to work. Work on better cache support is in progress.
+
+ IMPORTANT: loose caches (and by extension at the moment fscache)
+ do not necessarily validate cached values on the server. In other
+ words changes on the server are not guaranteed to be reflected
+ on the client system. Only use this mode of operation if you
+ have an exclusive mount and the server will modify the filesystem
+ underneath you.
debug=n specifies debug level. The debug level is a bitmask.
@@ -137,6 +157,12 @@ Options
This can be used to share devices/named pipes/sockets between
hosts. This functionality will be expanded in later versions.
+ directio bypass page cache on all read/write operations
+
+ ignoreqv ignore qid.version==0 as a marker to ignore cache
+
+ noxattr do not offer xattr functions on this mount.
+
access there are four access modes.
user
if a user tries to access a file on v9fs