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

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
 --------------------------------------------