Nobody checks the error flag on fuse folios, so stop setting it.
Optimise the (optional) setting of the uptodate flag and clearing
of the lock flag by using folio_end_read().

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

There is a confusion with fuse_file_uncached_io_{start,end} interface.
These helpers do two things when called from passthrough open()/release():
1. Take/drop negative refcount of fi->iocachectr (inode uncached io mode)
2. State change ff->iomode IOM_NONE <-> IOM_UNCACHED (file uncached open)

The calls from parallel dio write path need to take a reference on
fi->iocachectr, but they should not be changing ff->iomode state, because
in this case, the fi->iocachectr reference does not stick around until file
release().

Factor out helpers fuse_inode_uncached_io_{start,end}, to be used from
parallel dio write path and rename fuse_file_*cached_io_{start,end} helpers
to fuse_file_*cached_io_{open,release} to clarify the difference.

Fixes: 205c1d802683 ("fuse: allow parallel dio writes with FUSE_DIRECT_IO_ALLOW_MMAP")
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Pull fuse updates from Miklos Szeredi:

 - Add passthrough mode for regular file I/O.

   This allows performing read and write (also via memory maps) on a
   backing file without incurring the overhead of roundtrips to
   userspace. For now this is only allowed to privileged servers, but
   this limitation will go away in the future (Amir Goldstein)

 - Fix interaction of direct I/O mode with memory maps (Bernd Schubert)

 - Export filesystem tags through sysfs for virtiofs (Stefan Hajnoczi)

 - Allow resending queued requests for server crash recovery (Zhao Chen)

 - Misc fixes and cleanups

* tag 'fuse-update-6.9' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse: (38 commits)
  fuse: get rid of ff->readdir.lock
  fuse: remove unneeded lock which protecting update of congestion_threshold
  fuse: Fix missing FOLL_PIN for direct-io
  fuse: remove an unnecessary if statement
  fuse: Track process write operations in both direct and writethrough modes
  fuse: Use the high bit of request ID for indicating resend requests
  fuse: Introduce a new notification type for resend pending requests
  fuse: add support for explicit export disabling
  fuse: __kuid_val/__kgid_val helpers in fuse_fill_attr_from_inode()
  fuse: fix typo for fuse_permission comment
  fuse: Convert fuse_writepage_locked to take a folio
  fuse: Remove fuse_writepage
  virtio_fs: remove duplicate check if queue is broken
  fuse: use FUSE_ROOT_ID in fuse_get_root_inode()
  fuse: don't unhash root
  fuse: fix root lookup with nonzero generation
  fuse: replace remaining make_bad_inode() with fuse_make_bad()
  virtiofs: drop __exit from virtio_fs_sysfs_exit()
  fuse: implement passthrough for mmap
  fuse: implement splice read/write passthrough
  ...

The same protection is provided by file->f_pos_lock.

Note, this relies on the fact that file->f_mode has FMODE_ATOMIC_POS.
This flag is cleared by stream_open(), which would prevent locking of
f_pos_lock.

Prior to commit 7de64d521bf9 ("fuse: break up fuse_open_common()")
FOPEN_STREAM on a directory would cause stream_open() to be called.
After this commit this is not done anymore, so f_pos_lock will always
be locked.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Our user space filesystem relies on fuse to provide POSIX interface.
In our test, a known string is written into a file and the content
is read back later to verify correct data returned. We observed wrong
data returned in read buffer in rare cases although correct data are
stored in our filesystem.

Fuse kernel module calls iov_iter_get_pages2() to get the physical
pages of the user-space read buffer passed in read(). The pages are
not pinned to avoid page migration. When page migration occurs, the
consequence are two-folds.

1) Applications do not receive correct data in read buffer.
2) fuse kernel writes data into a wrong place.

Using iov_iter_extract_pages() to pin pages fixes the issue in our
test.

An auxiliary variable "struct page **pt_pages" is used in the patch
to prepare the 2nd parameter for iov_iter_extract_pages() since
iov_iter_get_pages2() uses a different type for the 2nd parameter.

[SzM] add iov_iter_extract_will_pin(ii) and unpin only if true.

Signed-off-by: Lei Huang <lei.huang@linux.intel.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

FUSE remote locking code paths never add any locking state to
inode->i_flctx, so the locks_remove_posix() function called on
file close will return without calling fuse_setlk().

Therefore, as the if statement to be removed in this commit will
always be false, remove it for clearness.

Signed-off-by: Jiachen Zhang <zhangjiachen.jaycee@bytedance.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Due to the fact that fuse does not count the write IO of processes in the
direct and writethrough write modes, user processes cannot track
write_bytes through the “/proc/[pid]/io” path. For example, the system
tool iotop cannot count the write operations of the corresponding process.

Signed-off-by: Zhou Jifeng <zhoujifeng@kylinos.com.cn>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

The one remaining caller of fuse_writepage_locked() already has a folio,
so convert this function entirely.  Saves a few calls to compound_head()
but no attempt is made to support large folios in this patch.

Signed-off-by: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

The writepage operation is deprecated as it leads to worse performance
under high memory pressure due to folios being written out in LRU order
rather than sequentially within a file.  Use filemap_migrate_folio() to
support dirty folio migration instead of writepage.

Signed-off-by: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

An mmap request for a file open in passthrough mode, maps the memory
directly to the backing file.

An mmap of a file in direct io mode, usually uses cached mmap and puts
the inode in caching io mode, which denies new passthrough opens of that
inode, because caching io mode is conflicting with passthrough io mode.

For the same reason, trying to mmap a direct io file, while there is
a passthrough file open on the same inode will fail with -ENODEV.

An mmap of a file in direct io mode, also needs to wait for parallel
dio writes in-progress to complete.

If a passthrough file is opened, while an mmap of another direct io
file is waiting for parallel dio writes to complete, the wait is aborted
and mmap fails with -ENODEV.

A FUSE server that uses passthrough and direct io opens on the same inode
that may also be mmaped, is advised to provide a backing fd also for the
files that are open in direct io mode (i.e. use the flags combination
FOPEN_DIRECT_IO | FOPEN_PASSTHROUGH), so that mmap will always use the
backing file, even if read/write do not passthrough.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>