linux.git/fs/fuse/file.c, branch v5.15

Merge tag 'fuse-update-5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse

2021-09-07T19:18:29+00:00

Pull fuse updates from Miklos Szeredi:

 - Allow mounting an active fuse device. Previously the fuse device
   would always be mounted during initialization, and sharing a fuse
   superblock was only possible through mount or namespace cloning

 - Fix data flushing in syncfs (virtiofs only)

 - Fix data flushing in copy_file_range()

 - Fix a possible deadlock in atomic O_TRUNC

 - Misc fixes and cleanups

* tag 'fuse-update-5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse:
  fuse: remove unused arg in fuse_write_file_get()
  fuse: wait for writepages in syncfs
  fuse: flush extending writes
  fuse: truncate pagecache on atomic_o_trunc
  fuse: allow sharing existing sb
  fuse: move fget() to fuse_get_tree()
  fuse: move option checking into fuse_fill_super()
  fuse: name fs_context consistently
  fuse: fix use after free in fuse_read_interrupt()

fuse: remove unused arg in fuse_write_file_get()

2021-09-06T11:37:10+00:00

The struct fuse_conn argument is not used and can be removed.

Signed-off-by: Miklos Szeredi

fuse: wait for writepages in syncfs

2021-09-06T11:37:02+00:00

In case of fuse the MM subsystem doesn't guarantee that page writeback
completes by the time ->sync_fs() is called.  This is because fuse
completes page writeback immediately to prevent DoS of memory reclaim by
the userspace file server.

This means that fuse itself must ensure that writes are synced before
sending the SYNCFS request to the server.

Introduce sync buckets, that hold a counter for the number of outstanding
write requests.  On syncfs replace the current bucket with a new one and
wait until the old bucket's counter goes down to zero.

It is possible to have multiple syncfs calls in parallel, in which case
there could be more than one waited-on buckets.  Descendant buckets must
not complete until the parent completes.  Add a count to the child (new)
bucket until the (parent) old bucket completes.

Use RCU protection to dereference the current bucket and to wake up an
emptied bucket.  Use fc->lock to protect against parallel assignments to
the current bucket.

This leaves just the counter to be a possible scalability issue.  The
fc->num_waiting counter has a similar issue, so both should be addressed at
the same time.

Reported-by: Amir Goldstein 
Fixes: 2d82ab251ef0 ("virtiofs: propagate sync() to file server")
Cc:  # v5.14
Signed-off-by: Miklos Szeredi

fuse: flush extending writes

2021-08-31T12:18:08+00:00

Callers of fuse_writeback_range() assume that the file is ready for
modification by the server in the supplied byte range after the call
returns.

If there's a write that extends the file beyond the end of the supplied
range, then the file needs to be extended to at least the end of the range,
but currently that's not done.

There are at least two cases where this can cause problems:

 - copy_file_range() will return short count if the file is not extended
   up to end of the source range.

 - FALLOC_FL_ZERO_RANGE | FALLOC_FL_KEEP_SIZE will not extend the file,
   hence the region may not be fully allocated.

Fix by flushing writes from the start of the range up to the end of the
file.  This could be optimized if the writes are non-extending, etc, but
it's probably not worth the trouble.

Fixes: a2bc92362941 ("fuse: fix copy_file_range() in the writeback case")
Fixes: 6b1bdb56b17c ("fuse: allow fallocate(FALLOC_FL_ZERO_RANGE)")
Cc:   # v5.2
Signed-off-by: Miklos Szeredi

fuse: truncate pagecache on atomic_o_trunc

2021-08-17T19:05:16+00:00

fuse_finish_open() will be called with FUSE_NOWRITE in case of atomic
O_TRUNC.  This can deadlock with fuse_wait_on_page_writeback() in
fuse_launder_page() triggered by invalidate_inode_pages2().

Fix by replacing invalidate_inode_pages2() in fuse_finish_open() with a
truncate_pagecache() call.  This makes sense regardless of FOPEN_KEEP_CACHE
or fc->writeback cache, so do it unconditionally.

Reported-by: Xie Yongji 
Reported-and-tested-by: syzbot+bea44a5189836d956894@syzkaller.appspotmail.com
Fixes: e4648309b85a ("fuse: truncate pending writes on O_TRUNC")
Cc: 
Signed-off-by: Miklos Szeredi

fuse: Convert to using invalidate_lock

2021-07-13T12:29:01+00:00

Use invalidate_lock instead of fuse's private i_mmap_sem. The intended
purpose is exactly the same. By this conversion we fix a long standing
race between hole punching and read(2) / readahead(2) paths that can
lead to stale page cache contents.

CC: Miklos Szeredi 
Reviewed-by: Miklos Szeredi 
Signed-off-by: Jan Kara

Merge tag 'fuse-update-5.14' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse

2021-07-06T18:17:41+00:00

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

virtiofs: Fix spelling mistakes

2021-06-22T07:15:36+00:00

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

Signed-off-by: Zheng Yongjun 
Signed-off-by: Miklos Szeredi

fuse: use DIV_ROUND_UP helper macro for calculations

2021-06-22T07:15:36+00:00

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

Signed-off-by: Wu Bo 
Signed-off-by: Miklos Szeredi

fuse: allow fallocate(FALLOC_FL_ZERO_RANGE)

2021-06-22T07:15:36+00:00

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 
Signed-off-by: Miklos Szeredi