Pull fuse updates from Miklos Szeredi:

 - Fixes for virtiofs submounts

 - Misc fixes and cleanups

* tag 'fuse-update-5.14' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse:
  virtiofs: Fix spelling mistakes
  fuse: use DIV_ROUND_UP helper macro for calculations
  fuse: fix illegal access to inode with reused nodeid
  fuse: allow fallocate(FALLOC_FL_ZERO_RANGE)
  fuse: Make fuse_fill_super_submount() static
  fuse: Switch to fc_mount() for submounts
  fuse: Call vfs_get_tree() for submounts
  fuse: add dedicated filesystem context ops for submounts
  virtiofs: propagate sync() to file server
  fuse: reject internal errno
  fuse: check connected before queueing on fpq->io
  fuse: ignore PG_workingset after stealing
  fuse: Fix infinite loop in sget_fc()
  fuse: Fix crash if superblock of submount gets killed early
  fuse: Fix crash in fuse_dentry_automount() error path

Fix some spelling mistakes in comments:
refernce  ==> reference
happnes  ==> happens
threhold  ==> threshold
splitted  ==> split
mached  ==> matched

Signed-off-by: Zheng Yongjun <zhengyongjun3@huawei.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Replace open coded divisor calculations with the DIV_ROUND_UP kernel macro
for better readability.

Signed-off-by: Wu Bo <wubo40@huawei.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

The current fuse module filters out fallocate(FALLOC_FL_ZERO_RANGE)
returning -EOPNOTSUPP.  libnbd's nbdfuse would like to translate
FALLOC_FL_ZERO_RANGE requests into the NBD command
NBD_CMD_WRITE_ZEROES which allows NBD servers that support it to do
zeroing efficiently.

This commit treats this flag exactly like FALLOC_FL_PUNCH_HOLE.

A way to test this, requiring fuse >= 3, nbdkit >= 1.8 and the latest
nbdfuse from https://gitlab.com/nbdkit/libnbd/-/tree/master/fuse is to
create a file containing some data and "mirror" it to a fuse file:

  $ dd if=/dev/urandom of=disk.img bs=1M count=1
  $ nbdkit file disk.img
  $ touch mirror.img
  $ nbdfuse mirror.img nbd://localhost &

(mirror.img -> nbdfuse -> NBD over loopback -> nbdkit -> disk.img)

You can then run commands such as:

  $ fallocate -z -o 1024 -l 1024 mirror.img

and check that the content of the original file ("disk.img") stays
synchronized.  To show NBD commands, export LIBNBD_DEBUG=1 before
running nbdfuse.  To clean up:

  $ fusermount3 -u mirror.img
  $ killall nbdkit

Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Replacement is called copy_page_from_iter_atomic(); unlike the old primitive the
callers do *not* need to do iov_iter_advance() after it.  In case when they end
up consuming less than they'd been given they need to do iov_iter_revert() on
everything they had not consumed.  That, however, needs to be done only on slow
paths.

All in-tree callers converted.  And that kills the last user of iterate_all_kinds()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

another rudiment of fault-in originally having been limited to the
first segment, same as in generic_perform_write() and friends.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Pull fuse updates from Miklos Szeredi:

 - Fix a page locking bug in write (introduced in 2.6.26)

 - Allow sgid bit to be killed in setacl()

 - Miscellaneous fixes and cleanups

* tag 'fuse-update-5.13' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse:
  cuse: simplify refcount
  cuse: prevent clone
  virtiofs: fix userns
  virtiofs: remove useless function
  virtiofs: split requests that exceed virtqueue size
  virtiofs: fix memory leak in virtio_fs_probe()
  fuse: invalidate attrs when page writeback completes
  fuse: add a flag FUSE_SETXATTR_ACL_KILL_SGID to kill SGID
  fuse: extend FUSE_SETXATTR request
  fuse: fix matching of FUSE_DEV_IOC_CLONE command
  fuse: fix a typo
  fuse: don't zero pages twice
  fuse: fix typo for fuse_conn.max_pages comment
  fuse: fix write deadlock

In fuse when a direct/write-through write happens we invalidate attrs
because that might have updated mtime/ctime on server and cached
mtime/ctime will be stale.

What about page writeback path.  Looks like we don't invalidate attrs
there.  To be consistent, invalidate attrs in writeback path as well.  Only
exception is when writeback_cache is enabled.  In that case we strust local
mtime/ctime and there is no need to invalidate attrs.

Recently users started experiencing failure of xfstests generic/080,
geneirc/215 and generic/614 on virtiofs.  This happened only newer "stat"
utility and not older one.  This patch fixes the issue.

So what's the root cause of the issue.  Here is detailed explanation.

generic/080 test does mmap write to a file, closes the file and then checks
if mtime has been updated or not.  When file is closed, it leads to
flushing of dirty pages (and that should update mtime/ctime on server).
But we did not explicitly invalidate attrs after writeback finished.  Still
generic/080 passed so far and reason being that we invalidated atime in
fuse_readpages_end().  This is called in fuse_readahead() path and always
seems to trigger before mmaped write.

So after mmaped write when lstat() is called, it sees that atleast one of
the fields being asked for is invalid (atime) and that results in
generating GETATTR to server and mtime/ctime also get updated and test
passes.

But newer /usr/bin/stat seems to have moved to using statx() syscall now
(instead of using lstat()).  And statx() allows it to query only ctime or
mtime (and not rest of the basic stat fields).  That means when querying
for mtime, fuse_update_get_attr() sees that mtime is not invalid (only
atime is invalid).  So it does not generate a new GETATTR and fill stat
with cached mtime/ctime.  And that means updated mtime is not seen by
xfstest and tests start failing.

Invalidating attrs after writeback completion should solve this problem in
a generic manner.

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

All callers of fuse_short_read already set the .page_zeroing flag, so no
need to do the tail zeroing again.

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

There are two modes for write(2) and friends in fuse:

a) write through (update page cache, send sync WRITE request to userspace)

b) buffered write (update page cache, async writeout later)

The write through method kept all the page cache pages locked that were
used for the request.  Keeping more than one page locked is deadlock prone
and Qian Cai demonstrated this with trinity fuzzing.

The reason for keeping the pages locked is that concurrent mapped reads
shouldn't try to pull possibly stale data into the page cache.

For full page writes, the easy way to fix this is to make the cached page
be the authoritative source by marking the page PG_uptodate immediately.
After this the page can be safely unlocked, since mapped/cached reads will
take the written data from the cache.

Concurrent mapped writes will now cause data in the original WRITE request
to be updated; this however doesn't cause any data inconsistency and this
scenario should be exceedingly rare anyway.

If the WRITE request returns with an error in the above case, currently the
page is not marked uptodate; this means that a concurrent read will always
read consistent data.  After this patch the page is uptodate between
writing to the cache and receiving the error: there's window where a cached
read will read the wrong data.  While theoretically this could be a
regression, it is unlikely to be one in practice, since this is normal for
buffered writes.

In case of a partial page write to an already uptodate page the locking is
also unnecessary, with the above caveats.

Partial write of a not uptodate page still needs to be handled.  One way
would be to read the complete page before doing the write.  This is not
possible, since it might break filesystems that don't expect any READ
requests when the file was opened O_WRONLY.

The other solution is to serialize the synchronous write with reads from
the partial pages.  The easiest way to do this is to keep the partial pages
locked.  The problem is that a write() may involve two such pages (one head
and one tail).  This patch fixes it by only locking the partial tail page.
If there's a partial head page as well, then split that off as a separate
WRITE request.

Reported-by: Qian Cai <cai@lca.pw>
Link: https://lore.kernel.org/linux-fsdevel/4794a3fa3742a5e84fb0f934944204b55730829b.camel@lca.pw/
Fixes: ea9b9907b82a ("fuse: implement perform_write")
Cc: <stable@vger.kernel.org> # v2.6.26
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>