linux-stable.git/fs/fuse/inode.c, branch linux-5.4.y

fuse: don't unhash root

2024-04-13T10:51:25+00:00

[ Upstream commit b1fe686a765e6c0d71811d825b5a1585a202b777 ]

The root inode is assumed to be always hashed.  Do not unhash the root
inode even if it is marked BAD.

Fixes: 5d069dbe8aaf ("fuse: fix bad inode")
Cc:  # v5.11
Signed-off-by: Miklos Szeredi 
Signed-off-by: Sasha Levin

fuse: limit nsec

2022-08-25T09:17:24+00:00

commit 47912eaa061a6a81e4aa790591a1874c650733c0 upstream.

Limit nanoseconds to 0..999999999.

Fixes: d8a5ba45457e ("[PATCH] FUSE - core")
Cc: 
Signed-off-by: Miklos Szeredi 
Signed-off-by: Greg Kroah-Hartman

fuse: fix bad inode

2021-01-09T12:44:54+00:00

[ Upstream commit 5d069dbe8aaf2a197142558b6fb2978189ba3454 ]

Jan Kara's analysis of the syzbot report (edited):

  The reproducer opens a directory on FUSE filesystem, it then attaches
  dnotify mark to the open directory.  After that a fuse_do_getattr() call
  finds that attributes returned by the server are inconsistent, and calls
  make_bad_inode() which, among other things does:

          inode->i_mode = S_IFREG;

  This then confuses dnotify which doesn't tear down its structures
  properly and eventually crashes.

Avoid calling make_bad_inode() on a live inode: switch to a private flag on
the fuse inode.  Also add the test to ops which the bad_inode_ops would
have caught.

This bug goes back to the initial merge of fuse in 2.6.14...

Reported-by: syzbot+f427adf9324b92652ccc@syzkaller.appspotmail.com
Signed-off-by: Miklos Szeredi 
Tested-by: Jan Kara 
Cc: 
Signed-off-by: Sasha Levin

fuse: update attr_version counter on fuse_notify_inval_inode()

2020-10-01T11:18:02+00:00

[ Upstream commit 5ddd9ced9aef6cfa76af27d384c17c9e2d610ce8 ]

A GETATTR request can race with FUSE_NOTIFY_INVAL_INODE, resulting in the
attribute cache being updated with stale information after the
invalidation.

Fix this by bumping the attribute version in fuse_reverse_inval_inode().

Reported-by: Krzysztof Rusek 
Signed-off-by: Miklos Szeredi 
Signed-off-by: Sasha Levin

fuse: use ->reconfigure() instead of ->remount_fs()

2020-07-22T07:33:12+00:00

commit 0189a2d367f49729622fdafaef5da73161591859 upstream.

s_op->remount_fs() is only called from legacy_reconfigure(), which is not
used after being converted to the new API.

Convert to using ->reconfigure().  This restores the previous behavior of
syncing the filesystem and rejecting MS_MANDLOCK on remount.

Fixes: c30da2e981a7 ("fuse: convert to use the new mount API")
Cc:  # v5.4
Signed-off-by: Miklos Szeredi 
Signed-off-by: Greg Kroah-Hartman

fuse: ignore 'data' argument of mount(..., MS_REMOUNT)

2020-07-22T07:33:12+00:00

commit e8b20a474cf2c42698d1942f939ff2128819f151 upstream.

The command

  mount -o remount -o unknownoption /mnt/fuse

succeeds on kernel versions prior to v5.4 and fails on kernel version at or
after.  This is because fuse_parse_param() rejects any unrecognised options
in case of FS_CONTEXT_FOR_RECONFIGURE, just as for FS_CONTEXT_FOR_MOUNT.

This causes a regression in case the fuse filesystem is in fstab, since
remount sends all options found there to the kernel; even ones that are
meant for the initial mount and are consumed by the userspace fuse server.

Fix this by ignoring mount options, just as fuse_remount_fs() did prior to
the conversion to the new API.

Reported-by: Stefan Priebe 
Fixes: c30da2e981a7 ("fuse: convert to use the new mount API")
Cc:  # v5.4
Signed-off-by: Miklos Szeredi 
Signed-off-by: Greg Kroah-Hartman

virtio-fs: don't show mount options

2019-10-15T14:11:41+00:00

Virtio-fs does not accept any mount options, so it's confusing and wrong to
show any in /proc/mounts.

Reported-by: Stefan Hajnoczi  
Signed-off-by: Miklos Szeredi

Merge tag 'virtio-fs-5.4' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse

2019-09-27T22:54:24+00:00

Pull fuse virtio-fs support from Miklos Szeredi:
 "Virtio-fs allows exporting directory trees on the host and mounting
  them in guest(s).

  This isn't actually a new filesystem, but a glue layer between the
  fuse filesystem and a virtio based back-end.

  It's similar in functionality to the existing virtio-9p solution, but
  significantly faster in benchmarks and has better POSIX compliance.
  Further permformance improvements can be achieved by sharing the page
  cache between host and guest, allowing for faster I/O and reduced
  memory use.

  Kata Containers have been including the out-of-tree virtio-fs (with
  the shared page cache patches as well) since version 1.7 as an
  experimental feature. They have been active in development and plan to
  switch from virtio-9p to virtio-fs as their default solution. There
  has been interest from other sources as well.

  The userspace infrastructure is slated to be merged into qemu once the
  kernel part hits mainline.

  This was developed by Vivek Goyal, Dave Gilbert and Stefan Hajnoczi"

* tag 'virtio-fs-5.4' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse:
  virtio-fs: add virtiofs filesystem
  virtio-fs: add Documentation/filesystems/virtiofs.rst
  fuse: reserve values for mapping protocol

fuse: kmemcg account fs data

2019-09-24T13:28:01+00:00

account per-file, dentry, and inode data

blockdev/superblock and temporary per-request data was left alone, as
this usually isn't accounted

Reviewed-by: Shakeel Butt 
Signed-off-by: Khazhismel Kumykov 
Signed-off-by: Miklos Szeredi

virtio-fs: add virtiofs filesystem

2019-09-18T18:17:50+00:00

Add a basic file system module for virtio-fs.  This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.

Design Overview
===============

With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.

 - Use fuse protocol (instead of 9p) for communication between guest and
   host.  Guest kernel will be fuse client and a fuse server will run on
   host to serve the requests.

 - For data access inside guest, mmap portion of file in QEMU address space
   and guest accesses this memory using dax.  That way guest page cache is
   bypassed and there is only one copy of data (on host).  This will also
   enable mmap(MAP_SHARED) between guests.

 - For metadata coherency, there is a shared memory region which contains
   version number associated with metadata and any guest changing metadata
   updates version number and other guests refresh metadata on next access.
   This is yet to be implemented.

How virtio-fs differs from existing approaches
==============================================

The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).

DAX allows file contents to be accessed without communication with the
hypervisor.  The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.

By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols.  In addition, this also makes it easier to achieve
local file system semantics (coherency).

These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine.  This is why we decided to build virtio-fs rather than
focus on 9P or NFS.

Caching Modes
=============

Like virtio-9p, different caching modes are supported which determine the
coherency level as well.  The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.

 - cache=none
   metadata, data and pathname lookup are not cached in guest.  They are
   always fetched from host and any changes are immediately pushed to host.

 - cache=always
   metadata, data and pathname lookup are cached in guest and never expire.

 - cache=auto
   metadata and pathname lookup cache expires after a configured amount of
   time (default is 1 second).  Data is cached while the file is open
   (close to open consistency).

 - writeback/no_writeback
   These options control the writeback strategy.  If writeback is disabled,
   then normal writes will immediately be synchronized with the host fs.
   If writeback is enabled, then writes may be cached in the guest until
   the file is closed or an fsync(2) performed.  This option has no effect
   on mmap-ed writes or writes going through the DAX mechanism.

Signed-off-by: Stefan Hajnoczi 
Signed-off-by: Vivek Goyal 
Acked-by: Michael S. Tsirkin 
Signed-off-by: Miklos Szeredi