linux-stable.git/fs/fuse/dir.c, branch linux-6.13.y

fuse: fix dax truncate/punch_hole fault path

2025-04-10T12:41:48+00:00

[ Upstream commit 7851bf649d423edd7286b292739f2eefded3d35c ]

Patch series "fs/dax: Fix ZONE_DEVICE page reference counts", v9.

Device and FS DAX pages have always maintained their own page reference
counts without following the normal rules for page reference counting.  In
particular pages are considered free when the refcount hits one rather
than zero and refcounts are not added when mapping the page.

Tracking this requires special PTE bits (PTE_DEVMAP) and a secondary
mechanism for allowing GUP to hold references on the page (see
get_dev_pagemap).  However there doesn't seem to be any reason why FS DAX
pages need their own reference counting scheme.

By treating the refcounts on these pages the same way as normal pages we
can remove a lot of special checks.  In particular pXd_trans_huge()
becomes the same as pXd_leaf(), although I haven't made that change here.
It also frees up a valuable SW define PTE bit on architectures that have
devmap PTE bits defined.

It also almost certainly allows further clean-up of the devmap managed
functions, but I have left that as a future improvment.  It also enables
support for compound ZONE_DEVICE pages which is one of my primary
motivators for doing this work.

This patch (of 20):

FS DAX requires file systems to call into the DAX layout prior to
unlinking inodes to ensure there is no ongoing DMA or other remote access
to the direct mapped page.  The fuse file system implements
fuse_dax_break_layouts() to do this which includes a comment indicating
that passing dmap_end == 0 leads to unmapping of the whole file.

However this is not true - passing dmap_end == 0 will not unmap anything
before dmap_start, and further more dax_layout_busy_page_range() will not
scan any of the range to see if there maybe ongoing DMA access to the
range.  Fix this by passing -1 for dmap_end to fuse_dax_break_layouts()
which will invalidate the entire file range to
dax_layout_busy_page_range().

Link: https://lkml.kernel.org/r/cover.8068ad144a7eea4a813670301f4d2a86a8e68ec4.1740713401.git-series.apopple@nvidia.com
Link: https://lkml.kernel.org/r/f09a34b6c40032022e4ddee6fadb7cc676f08867.1740713401.git-series.apopple@nvidia.com
Fixes: 6ae330cad6ef ("virtiofs: serialize truncate/punch_hole and dax fault path")
Signed-off-by: Alistair Popple 
Co-developed-by: Dan Williams 
Signed-off-by: Dan Williams 
Reviewed-by: Balbir Singh 
Tested-by: Alison Schofield 
Cc: Vivek Goyal 
Cc: Alexander Gordeev 
Cc: Asahi Lina 
Cc: Bjorn Helgaas 
Cc: Catalin Marinas 
Cc: Christian Borntraeger 
Cc: Christoph Hellwig 
Cc: Chunyan Zhang 
Cc: "Darrick J. Wong" 
Cc: Dave Chinner 
Cc: Dave Hansen 
Cc: Dave Jiang 
Cc: David Hildenbrand 
Cc: Gerald Schaefer 
Cc: Heiko Carstens 
Cc: Huacai Chen 
Cc: Ira Weiny 
Cc: Jan Kara 
Cc: Jason Gunthorpe 
Cc: Jason Gunthorpe 
Cc: John Hubbard 
Cc: linmiaohe 
Cc: Logan Gunthorpe 
Cc: Matthew Wilcow (Oracle) 
Cc: Michael "Camp Drill Sergeant" Ellerman 
Cc: Nicholas Piggin 
Cc: Peter Xu 
Cc: Sven Schnelle 
Cc: Ted Ts'o 
Cc: Vasily Gorbik 
Cc: Vishal Verma 
Cc: WANG Xuerui 
Cc: Will Deacon 
Signed-off-by: Andrew Morton 
Signed-off-by: Sasha Levin

fuse: don't truncate cached, mutated symlink

2025-03-22T19:56:51+00:00

[ Upstream commit b4c173dfbb6c78568578ff18f9e8822d7bd0e31b ]

Fuse allows the value of a symlink to change and this property is exploited
by some filesystems (e.g. CVMFS).

It has been observed, that sometimes after changing the symlink contents,
the value is truncated to the old size.

This is caused by fuse_getattr() racing with fuse_reverse_inval_inode().
fuse_reverse_inval_inode() updates the fuse_inode's attr_version, which
results in fuse_change_attributes() exiting before updating the cached
attributes

This is okay, as the cached attributes remain invalid and the next call to
fuse_change_attributes() will likely update the inode with the correct
values.

The reason this causes problems is that cached symlinks will be
returned through page_get_link(), which truncates the symlink to
inode->i_size.  This is correct for filesystems that don't mutate
symlinks, but in this case it causes bad behavior.

The solution is to just remove this truncation.  This can cause a
regression in a filesystem that relies on supplying a symlink larger than
the file size, but this is unlikely.  If that happens we'd need to make
this behavior conditional.

Reported-by: Laura Promberger 
Tested-by: Sam Lewis 
Signed-off-by: Miklos Szeredi 
Link: https://lore.kernel.org/r/20250220100258.793363-1-mszeredi@redhat.com
Reviewed-by: Bernd Schubert 
Signed-off-by: Christian Brauner 
Signed-off-by: Sasha Levin

fuse: respect FOPEN_KEEP_CACHE on opendir

2025-01-04T08:58:14+00:00

The re-factoring of fuse_dir_open() missed the need to invalidate
directory inode page cache with open flag FOPEN_KEEP_CACHE.

Fixes: 7de64d521bf92 ("fuse: break up fuse_open_common()")
Reported-by: Prince Kumar 
Closes: https://lore.kernel.org/linux-fsdevel/CAEW=TRr7CYb4LtsvQPLj-zx5Y+EYBmGfM24SuzwyDoGVNoKm7w@mail.gmail.com/
Signed-off-by: Amir Goldstein 
Link: https://lore.kernel.org/r/20250101130037.96680-1-amir73il@gmail.com
Reviewed-by: Bernd Schubert 
Signed-off-by: Christian Brauner

fuse: check attributes staleness on fuse_iget()

2024-11-18T11:24:13+00:00

Function fuse_direntplus_link() might call fuse_iget() to initialize a new
fuse_inode and change its attributes. If fi->attr_version is always
initialized with 0, even if the attributes returned by the FUSE_READDIR
request is staled, as the new fi->attr_version is 0, fuse_change_attributes
will still set the staled attributes to inode. This wrong behaviour may
cause file size inconsistency even when there is no changes from
server-side.

To reproduce the issue, consider the following 2 programs (A and B) are
running concurrently,

        A                                               B
----------------------------------      --------------------------------
{ /fusemnt/dir/f is a file path in a fuse mount, the size of f is 0. }

readdir(/fusemnt/dir) start
//Daemon set size 0 to f direntry
                                        fallocate(f, 1024)
                                        stat(f) // B see size 1024
                                        echo 2 > /proc/sys/vm/drop_caches
readdir(/fusemnt/dir) reply to kernel
Kernel set 0 to the I_NEW inode

                                        stat(f) // B see size 0

In the above case, only program B is modifying the file size, however, B
observes file size changing between the 2 'readonly' stat() calls. To fix
this issue, we should make sure readdirplus still follows the rule of
attr_version staleness checking even if the fi->attr_version is lost due to
inode eviction.

To identify this situation, the new fc->evict_ctr is used to record whether
the eviction of inodes occurs during the readdirplus request processing.
If it does, the result of readdirplus may be inaccurate; otherwise, the
result of readdirplus can be trusted. Although this may still lead to
incorrect invalidation, considering the relatively low frequency of
evict occurrences, it should be acceptable.

Link: https://lore.kernel.org/lkml/20230711043405.66256-2-zhangjiachen.jaycee@bytedance.com/
Link: https://lore.kernel.org/lkml/20241114070905.48901-1-zhangtianci.1997@bytedance.com/

Reported-by: Jiachen Zhang 
Suggested-by: Miklos Szeredi 
Signed-off-by: Zhang Tianci 
Signed-off-by: Miklos Szeredi

fuse: remove pages for requests and exclusively use folios

2024-11-05T13:08:35+00:00

All fuse requests use folios instead of pages for transferring data.
Remove pages from the requests and exclusively use folios.

No functional changes.

[SzM: rename back folio_descs -> descs, etc.]

Signed-off-by: Joanne Koong 
Reviewed-by: Josef Bacik 
Signed-off-by: Miklos Szeredi

fuse: convert readlink to use folios

2024-11-05T10:14:32+00:00

Convert readlink requests to use a folio instead of a page.

No functional changes.

Signed-off-by: Joanne Koong 
Reviewed-by: Josef Bacik 
Signed-off-by: Miklos Szeredi

fs/fuse: convert to use invalid_mnt_idmap

2024-09-23T09:10:26+00:00

We should convert fs/fuse code to use a newly introduced
invalid_mnt_idmap instead of passing a NULL as idmap pointer.

Suggested-by: Christian Brauner 
Signed-off-by: Alexander Mikhalitsyn 
Reviewed-by: Christian Brauner 
Signed-off-by: Miklos Szeredi

fs/fuse: introduce and use fuse_simple_idmap_request() helper

2024-09-23T09:07:55+00:00

Let's convert all existing callers properly.

No functional changes intended.

Suggested-by: Christian Brauner 
Signed-off-by: Alexander Mikhalitsyn 
Reviewed-by: Christian Brauner 
Signed-off-by: Miklos Szeredi

fuse: warn if fuse_access is called when idmapped mounts are allowed

2024-09-04T14:51:11+00:00

It is not possible with the current fuse code, but let's protect ourselves
from regressions in the future.

Signed-off-by: Alexander Mikhalitsyn 
Signed-off-by: Miklos Szeredi

fuse: support idmapped ->rename op

2024-09-04T14:51:11+00:00

RENAME_WHITEOUT is a special case of ->rename
and we need to take idmappings into account there.

Signed-off-by: Alexander Mikhalitsyn 
Signed-off-by: Miklos Szeredi