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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2022-01-12 22:30:58 +0100 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2022-01-12 22:30:58 +0100 |
| commit | 8975f8974888b3cd25aa8cf9eba24edbb9230bb2 (patch) | |
| tree | 1bcb933dafcf4e9bbee5c73bb3385b213bd92a79 /Documentation/filesystems | |
| parent | Merge tag 'fs_for_v5.17-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git... (diff) | |
| parent | Documentation/filesystem/dax: DAX on virtiofs (diff) | |
| download | linux-8975f8974888b3cd25aa8cf9eba24edbb9230bb2.tar.xz linux-8975f8974888b3cd25aa8cf9eba24edbb9230bb2.zip | |
Merge tag 'fuse-update-5.17' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse
Pull fuse updates from Miklos Szeredi:
- Fix a regression introduced in 5.15
- Extend the size of the FUSE_INIT request to accommodate for more
flags. There's a slight possibility of a regression for obscure fuse
servers; if this happens, then more complexity will need to be added
to the protocol
- Allow the DAX property to be controlled by the server on a per-inode
basis in virtiofs
- Allow sending security context to the server when creating a file or
directory
* tag 'fuse-update-5.17' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse:
Documentation/filesystem/dax: DAX on virtiofs
fuse: mark inode DONT_CACHE when per inode DAX hint changes
fuse: negotiate per inode DAX in FUSE_INIT
fuse: enable per inode DAX
fuse: support per inode DAX in fuse protocol
fuse: make DAX mount option a tri-state
fuse: add fuse_should_enable_dax() helper
fuse: Pass correct lend value to filemap_write_and_wait_range()
fuse: send security context of inode on file
fuse: extend init flags
Diffstat (limited to 'Documentation/filesystems')
| -rw-r--r-- | Documentation/filesystems/dax.rst | 20 |
1 files changed, 18 insertions, 2 deletions
diff --git a/Documentation/filesystems/dax.rst b/Documentation/filesystems/dax.rst index 9a1b8fd9e82b..e3b30429d703 100644 --- a/Documentation/filesystems/dax.rst +++ b/Documentation/filesystems/dax.rst @@ -23,8 +23,8 @@ on it as usual. The `DAX` code currently only supports files with a block size equal to your kernel's `PAGE_SIZE`, so you may need to specify a block size when creating the filesystem. -Currently 3 filesystems support `DAX`: ext2, ext4 and xfs. Enabling `DAX` on them -is different. +Currently 4 filesystems support `DAX`: ext2, ext4, xfs and virtiofs. +Enabling `DAX` on them is different. Enabling DAX on ext2 -------------------- @@ -168,6 +168,22 @@ if the underlying media does not support dax and/or the filesystem is overridden with a mount option. +Enabling DAX on virtiofs +---------------------------- +The semantic of DAX on virtiofs is basically equal to that on ext4 and xfs, +except that when '-o dax=inode' is specified, virtiofs client derives the hint +whether DAX shall be enabled or not from virtiofs server through FUSE protocol, +rather than the persistent `FS_XFLAG_DAX` flag. That is, whether DAX shall be +enabled or not is completely determined by virtiofs server, while virtiofs +server itself may deploy various algorithm making this decision, e.g. depending +on the persistent `FS_XFLAG_DAX` flag on the host. + +It is still supported to set or clear persistent `FS_XFLAG_DAX` flag inside +guest, but it is not guaranteed that DAX will be enabled or disabled for +corresponding file then. Users inside guest still need to call statx(2) and +check the statx flag `STATX_ATTR_DAX` to see if DAX is enabled for this file. + + Implementation Tips for Block Driver Writers -------------------------------------------- |