kernel/linux.git/fs/fuse, branch v6.6.132

fuse: fix readahead reclaim deadlock

2026-01-11T14:22:23+00:00

[ Upstream commit bd5603eaae0aabf527bfb3ce1bb07e979ce5bd50 ] Commit e26ee4efbc79 ("fuse: allocate ff->release_args only if release is needed") skips allocating ff->release_args if the server does not implement open. However in doing so, fuse_prepare_release() now skips grabbing the reference on the inode, which makes it possible for an inode to be evicted from the dcache while there are inflight readahead requests. This causes a deadlock if the server triggers reclaim while servicing the readahead request and reclaim attempts to evict the inode of the file being read ahead. Since the folio is locked during readahead, when reclaim evicts the fuse inode and fuse_evict_inode() attempts to remove all folios associated with the inode from the page cache (truncate_inode_pages_range()), reclaim will block forever waiting for the lock since readahead cannot relinquish the lock because it is itself blocked in reclaim: >>> stack_trace(1504735) folio_wait_bit_common (mm/filemap.c:1308:4) folio_lock (./include/linux/pagemap.h:1052:3) truncate_inode_pages_range (mm/truncate.c:336:10) fuse_evict_inode (fs/fuse/inode.c:161:2) evict (fs/inode.c:704:3) dentry_unlink_inode (fs/dcache.c:412:3) __dentry_kill (fs/dcache.c:615:3) shrink_kill (fs/dcache.c:1060:12) shrink_dentry_list (fs/dcache.c:1087:3) prune_dcache_sb (fs/dcache.c:1168:2) super_cache_scan (fs/super.c:221:10) do_shrink_slab (mm/shrinker.c:435:9) shrink_slab (mm/shrinker.c:626:10) shrink_node (mm/vmscan.c:5951:2) shrink_zones (mm/vmscan.c:6195:3) do_try_to_free_pages (mm/vmscan.c:6257:3) do_swap_page (mm/memory.c:4136:11) handle_pte_fault (mm/memory.c:5562:10) handle_mm_fault (mm/memory.c:5870:9) do_user_addr_fault (arch/x86/mm/fault.c:1338:10) handle_page_fault (arch/x86/mm/fault.c:1481:3) exc_page_fault (arch/x86/mm/fault.c:1539:2) asm_exc_page_fault+0x22/0x27 Fix this deadlock by allocating ff->release_args and grabbing the reference on the inode when preparing the file for release even if the server does not implement open. The inode reference will be dropped when the last reference on the fuse file is dropped (see fuse_file_put() -> fuse_release_end()). Fixes: e26ee4efbc79 ("fuse: allocate ff->release_args only if release is needed") Cc: stable@vger.kernel.org Signed-off-by: Joanne Koong Reported-by: Omar Sandoval Signed-off-by: Miklos Szeredi Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

fuse: Invalidate the page cache after FOPEN_DIRECT_IO write

2026-01-11T14:21:52+00:00

[ Upstream commit b359af8275a982a458e8df6c6beab1415be1f795 ] generic_file_direct_write() also does this and has a large comment about. Reproducer here is xfstest's generic/209, which is exactly to have competing DIO write and cached IO read. Signed-off-by: Bernd Schubert Signed-off-by: Miklos Szeredi Signed-off-by: Sasha Levin

fuse: Always flush the page cache before FOPEN_DIRECT_IO write

2026-01-11T14:21:52+00:00

[ Upstream commit 1ce120dcefc056ce8af2486cebbb77a458aad4c3 ] This was done as condition on direct_io_allow_mmap, but I believe this is not right, as a file might be open two times - once with write-back enabled another time with FOPEN_DIRECT_IO. Signed-off-by: Bernd Schubert Signed-off-by: Miklos Szeredi Signed-off-by: Sasha Levin

fuse: zero initialize inode private data

2025-11-24T09:29:30+00:00

[ Upstream commit 3ca1b311181072415b6432a169de765ac2034e5a ] This is slightly tricky, since the VFS uses non-zeroing allocation to preserve some fields that are left in a consistent state. Reported-by: Chunsheng Luo Closes: https://lore.kernel.org/all/20250818083224.229-1-luochunsheng@ustc.edu/ Signed-off-by: Miklos Szeredi Signed-off-by: Sasha Levin

fuse: fix livelock in synchronous file put from fuseblk workers

2025-10-29T13:07:06+00:00

[ Upstream commit 26e5c67deb2e1f42a951f022fdf5b9f7eb747b01 ] I observed a hang when running generic/323 against a fuseblk server. This test opens a file, initiates a lot of AIO writes to that file descriptor, and closes the file descriptor before the writes complete. Unsurprisingly, the AIO exerciser threads are mostly stuck waiting for responses from the fuseblk server: # cat /proc/372265/task/372313/stack [<0>] request_wait_answer+0x1fe/0x2a0 [fuse] [<0>] __fuse_simple_request+0xd3/0x2b0 [fuse] [<0>] fuse_do_getattr+0xfc/0x1f0 [fuse] [<0>] fuse_file_read_iter+0xbe/0x1c0 [fuse] [<0>] aio_read+0x130/0x1e0 [<0>] io_submit_one+0x542/0x860 [<0>] __x64_sys_io_submit+0x98/0x1a0 [<0>] do_syscall_64+0x37/0xf0 [<0>] entry_SYSCALL_64_after_hwframe+0x4b/0x53 But the /weird/ part is that the fuseblk server threads are waiting for responses from itself: # cat /proc/372210/task/372232/stack [<0>] request_wait_answer+0x1fe/0x2a0 [fuse] [<0>] __fuse_simple_request+0xd3/0x2b0 [fuse] [<0>] fuse_file_put+0x9a/0xd0 [fuse] [<0>] fuse_release+0x36/0x50 [fuse] [<0>] __fput+0xec/0x2b0 [<0>] task_work_run+0x55/0x90 [<0>] syscall_exit_to_user_mode+0xe9/0x100 [<0>] do_syscall_64+0x43/0xf0 [<0>] entry_SYSCALL_64_after_hwframe+0x4b/0x53 The fuseblk server is fuse2fs so there's nothing all that exciting in the server itself. So why is the fuse server calling fuse_file_put? The commit message for the fstest sheds some light on that: "By closing the file descriptor before calling io_destroy, you pretty much guarantee that the last put on the ioctx will be done in interrupt context (during I/O completion). Aha. AIO fgets a new struct file from the fd when it queues the ioctx. The completion of the FUSE_WRITE command from userspace causes the fuse server to call the AIO completion function. The completion puts the struct file, queuing a delayed fput to the fuse server task. When the fuse server task returns to userspace, it has to run the delayed fput, which in the case of a fuseblk server, it does synchronously. Sending the FUSE_RELEASE command sychronously from fuse server threads is a bad idea because a client program can initiate enough simultaneous AIOs such that all the fuse server threads end up in delayed_fput, and now there aren't any threads left to handle the queued fuse commands. Fix this by only using asynchronous fputs when closing files, and leave a comment explaining why. Cc: stable@vger.kernel.org # v2.6.38 Fixes: 5a18ec176c934c ("fuse: fix hang of single threaded fuseblk filesystem") Signed-off-by: Darrick J. Wong Signed-off-by: Miklos Szeredi Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

fuse: allocate ff->release_args only if release is needed

2025-10-29T13:07:06+00:00

[ Upstream commit e26ee4efbc79610b20e7abe9d96c87f33dacc1ff ] This removed the need to pass isdir argument to fuse_put_file(). Signed-off-by: Amir Goldstein Signed-off-by: Miklos Szeredi Stable-dep-of: 26e5c67deb2e ("fuse: fix livelock in synchronous file put from fuseblk workers") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

fuse: prevent overflow in copy_file_range return value

2025-09-19T14:32:04+00:00

commit 1e08938c3694f707bb165535df352ac97a8c75c9 upstream. The FUSE protocol uses struct fuse_write_out to convey the return value of copy_file_range, which is restricted to uint32_t. But the COPY_FILE_RANGE interface supports a 64-bit size copies. Currently the number of bytes copied is silently truncated to 32-bit, which may result in poor performance or even failure to copy in case of truncation to zero. Reported-by: Florian Weimer Closes: https://lore.kernel.org/all/lhuh5ynl8z5.fsf@oldenburg.str.redhat.com/ Fixes: 88bc7d5097a1 ("fuse: add support for copy_file_range()") Cc: # v4.20 Signed-off-by: Miklos Szeredi Signed-off-by: Greg Kroah-Hartman

fuse: check if copy_file_range() returns larger than requested size

2025-09-19T14:32:03+00:00

commit e5203209b3935041dac541bc5b37efb44220cc0b upstream. Just like write(), copy_file_range() should check if the return value is less or equal to the requested number of bytes. Reported-by: Chunsheng Luo Closes: https://lore.kernel.org/all/20250807062425.694-1-luochunsheng@ustc.edu/ Fixes: 88bc7d5097a1 ("fuse: add support for copy_file_range()") Cc: # v4.20 Signed-off-by: Miklos Szeredi Signed-off-by: Greg Kroah-Hartman

fuse: fix race between concurrent setattrs from multiple nodes

2025-07-06T09:00:06+00:00

[ Upstream commit 69efbff69f89c9b2b72c4d82ad8b59706add768a ] When mounting a user-space filesystem on multiple clients, after concurrent ->setattr() calls from different node, stale inode attributes may be cached in some node. This is caused by fuse_setattr() racing with fuse_reverse_inval_inode(). When filesystem server receives setattr request, the client node with valid iattr cached will be required to update the fuse_inode's attr_version and invalidate the cache by fuse_reverse_inval_inode(), and at the next call to ->getattr() they will be fetched from user space. The race scenario is: 1. client-1 sends setattr (iattr-1) request to server 2. client-1 receives the reply from server 3. before client-1 updates iattr-1 to the cached attributes by fuse_change_attributes_common(), server receives another setattr (iattr-2) request from client-2 4. server requests client-1 to update the inode attr_version and invalidate the cached iattr, and iattr-1 becomes staled 5. client-2 receives the reply from server, and caches iattr-2 6. continue with step 2, client-1 invokes fuse_change_attributes_common(), and caches iattr-1 The issue has been observed from concurrent of chmod, chown, or truncate, which all invoke ->setattr() call. The solution is to use fuse_inode's attr_version to check whether the attributes have been modified during the setattr request's lifetime. If so, mark the attributes as invalid in the function fuse_change_attributes_common(). Signed-off-by: Guang Yuan Wu Reviewed-by: Bernd Schubert Signed-off-by: Miklos Szeredi Signed-off-by: Sasha Levin

fuse: Return EPERM rather than ENOSYS from link()

2025-06-04T12:41:54+00:00

[ Upstream commit 8344213571b2ac8caf013cfd3b37bc3467c3a893 ] link() is documented to return EPERM when a filesystem doesn't support the operation, return that instead. Link: https://github.com/libfuse/libfuse/issues/925 Signed-off-by: Matt Johnston Signed-off-by: Miklos Szeredi Signed-off-by: Sasha Levin