[PATCH vfs.tmpfs 0/5] tmpfs: user xattrs and direct IO

[Hugh Dickins <hughd@google.com>]

This series enables and limits user extended attributes on tmpfs,
and independently provides a trivial direct IO stub for tmpfs.

It is here based on the vfs.tmpfs branch in vfs.git in next-20230808
but with a cherry-pick of v6.5-rc4's commit
253e5df8b8f0 ("tmpfs: fix Documentation of noswap and huge mount options")
first: since the vfs.tmpfs branch is based on v6.5-rc1, but 3/5 in this
series updates tmpfs.rst in a way which depends on that commit.

IIUC the right thing to do would be to cherry-pick 253e5df8b8f0 into
vfs.tmpfs before applying this series.  I'm sorry that the series as
posted does not apply cleanly to any known tree! but I think posting
it against v6.5-rc5 or next-20230808 would be even less helpful.

There is one "conflict" between this series and the final next-20230808:
Jeff Layton's vfs.ctime mods update a line of shmem_xattr_handler_set(),
where neighbouring lines are modified by 1/5 and 3/5 here: easily
resolved in the merge commit, I hope.

1/5 xattr: simple_xattr_set() return old_xattr to be freed
2/5 tmpfs: track free_ispace instead of free_inodes
3/5 tmpfs,xattr: enable limited user extended attributes
4/5 tmpfs: trivial support for direct IO
5/5 mm: invalidation check mapping before folio_contains

 Documentation/filesystems/tmpfs.rst |   7 +-
 fs/Kconfig                          |   4 +-
 fs/kernfs/dir.c                     |   2 +-
 fs/kernfs/inode.c                   |  46 +++++++----
 fs/xattr.c                          |  79 +++++++++++-------
 include/linux/shmem_fs.h            |   2 +-
 include/linux/xattr.h               |  10 ++-
 mm/shmem.c                          | 130 +++++++++++++++++++++++-------
 mm/truncate.c                       |   4 +-
 9 files changed, 197 insertions(+), 87 deletions(-)

Hugh