kernel/linux.git/fs/fuse/file.c, branch v6.12.80

fuse: fix readahead reclaim deadlock

2026-01-08T09:14:31+00:00

commit bd5603eaae0aabf527bfb3ce1bb07e979ce5bd50 upstream. 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: Greg Kroah-Hartman

fuse: Invalidate the page cache after FOPEN_DIRECT_IO write

2026-01-08T09:14:10+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

2026-01-08T09:14:10+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: fix livelock in synchronous file put from fuseblk workers

2025-10-19T14:33:50+00:00

commit 26e5c67deb2e1f42a951f022fdf5b9f7eb747b01 upstream. 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: Greg Kroah-Hartman

fuse: prevent overflow in copy_file_range return value

2025-09-19T14:35:46+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

2025-09-19T14:35:46+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 dax truncate/punch_hole fault path

2025-04-10T12:39:25+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

virtiofs: use pages instead of pointer for kernel direct IO

2024-12-05T13:02:21+00:00

[ Upstream commit 41748675c0bf252b3c5f600a95830f0936d366c1 ] When trying to insert a 10MB kernel module kept in a virtio-fs with cache disabled, the following warning was reported: ------------[ cut here ]------------ WARNING: CPU: 1 PID: 404 at mm/page_alloc.c:4551 ...... Modules linked in: CPU: 1 PID: 404 Comm: insmod Not tainted 6.9.0-rc5+ #123 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996) ...... RIP: 0010:__alloc_pages+0x2bf/0x380 ...... Call Trace: ? __warn+0x8e/0x150 ? __alloc_pages+0x2bf/0x380 __kmalloc_large_node+0x86/0x160 __kmalloc+0x33c/0x480 virtio_fs_enqueue_req+0x240/0x6d0 virtio_fs_wake_pending_and_unlock+0x7f/0x190 queue_request_and_unlock+0x55/0x60 fuse_simple_request+0x152/0x2b0 fuse_direct_io+0x5d2/0x8c0 fuse_file_read_iter+0x121/0x160 __kernel_read+0x151/0x2d0 kernel_read+0x45/0x50 kernel_read_file+0x1a9/0x2a0 init_module_from_file+0x6a/0xe0 idempotent_init_module+0x175/0x230 __x64_sys_finit_module+0x5d/0xb0 x64_sys_call+0x1c3/0x9e0 do_syscall_64+0x3d/0xc0 entry_SYSCALL_64_after_hwframe+0x4b/0x53 ...... ---[ end trace 0000000000000000 ]--- The warning is triggered as follows: 1) syscall finit_module() handles the module insertion and it invokes kernel_read_file() to read the content of the module first. 2) kernel_read_file() allocates a 10MB buffer by using vmalloc() and passes it to kernel_read(). kernel_read() constructs a kvec iter by using iov_iter_kvec() and passes it to fuse_file_read_iter(). 3) virtio-fs disables the cache, so fuse_file_read_iter() invokes fuse_direct_io(). As for now, the maximal read size for kvec iter is only limited by fc->max_read. For virtio-fs, max_read is UINT_MAX, so fuse_direct_io() doesn't split the 10MB buffer. It saves the address and the size of the 10MB-sized buffer in out_args[0] of a fuse request and passes the fuse request to virtio_fs_wake_pending_and_unlock(). 4) virtio_fs_wake_pending_and_unlock() uses virtio_fs_enqueue_req() to queue the request. Because virtiofs need DMA-able address, so virtio_fs_enqueue_req() uses kmalloc() to allocate a bounce buffer for all fuse args, copies these args into the bounce buffer and passed the physical address of the bounce buffer to virtiofsd. The total length of these fuse args for the passed fuse request is about 10MB, so copy_args_to_argbuf() invokes kmalloc() with a 10MB size parameter and it triggers the warning in __alloc_pages(): if (WARN_ON_ONCE_GFP(order > MAX_PAGE_ORDER, gfp)) return NULL; 5) virtio_fs_enqueue_req() will retry the memory allocation in a kworker, but it won't help, because kmalloc() will always return NULL due to the abnormal size and finit_module() will hang forever. A feasible solution is to limit the value of max_read for virtio-fs, so the length passed to kmalloc() will be limited. However it will affect the maximal read size for normal read. And for virtio-fs write initiated from kernel, it has the similar problem but now there is no way to limit fc->max_write in kernel. So instead of limiting both the values of max_read and max_write in kernel, introducing use_pages_for_kvec_io in fuse_conn and setting it as true in virtiofs. When use_pages_for_kvec_io is enabled, fuse will use pages instead of pointer to pass the KVEC_IO data. After switching to pages for KVEC_IO data, these pages will be used for DMA through virtio-fs. If these pages are backed by vmalloc(), {flush|invalidate}_kernel_vmap_range() are necessary to flush or invalidate the cache before the DMA operation. So add two new fields in fuse_args_pages to record the base address of vmalloc area and the condition indicating whether invalidation is needed. Perform the flush in fuse_get_user_pages() for write operations and the invalidation in fuse_release_user_pages() for read operations. It may seem necessary to introduce another field in fuse_conn to indicate that these KVEC_IO pages are used for DMA, However, considering that virtio-fs is currently the only user of use_pages_for_kvec_io, just reuse use_pages_for_kvec_io to indicate that these pages will be used for DMA. Fixes: a62a8ef9d97d ("virtio-fs: add virtiofs filesystem") Signed-off-by: Hou Tao Tested-by: Jingbo Xu Signed-off-by: Miklos Szeredi Signed-off-by: Sasha Levin

Revert "fuse: move initialization of fuse_file to fuse_writepages() instead of in callback"

2024-10-21T08:02:51+00:00

This reverts commit 672c3b7457fcee9656c36a29a4b21ec4a652433e. fuse_writepages() might be called with no dirty pages after all writable opens were closed. In this case __fuse_write_file_get() will return NULL which will trigger the WARNING. The exact conditions under which this is triggered is unclear and syzbot didn't find a reproducer yet. Reported-by: syzbot+217a976dc26ef2fa8711@syzkaller.appspotmail.com Link: https://lore.kernel.org/all/CAJnrk1aQwfvb51wQ5rUSf9N8j1hArTFeSkHqC_3T-mU6_BCD=A@mail.gmail.com/ Signed-off-by: Miklos Szeredi

Merge tag 'fuse-update-6.12' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse

2024-09-24T22:29:42+00:00

Pull fuse updates from Miklos Szeredi: - Add support for idmapped fuse mounts (Alexander Mikhalitsyn) - Add optimization when checking for writeback (yangyun) - Add tracepoints (Josef Bacik) - Clean up writeback code (Joanne Koong) - Clean up request queuing (me) - Misc fixes * tag 'fuse-update-6.12' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse: (32 commits) fuse: use exclusive lock when FUSE_I_CACHE_IO_MODE is set fuse: clear FR_PENDING if abort is detected when sending request fs/fuse: convert to use invalid_mnt_idmap fs/mnt_idmapping: introduce an invalid_mnt_idmap fs/fuse: introduce and use fuse_simple_idmap_request() helper fs/fuse: fix null-ptr-deref when checking SB_I_NOIDMAP flag fuse: allow O_PATH fd for FUSE_DEV_IOC_BACKING_OPEN virtio_fs: allow idmapped mounts fuse: allow idmapped mounts fuse: warn if fuse_access is called when idmapped mounts are allowed fuse: handle idmappings properly in ->write_iter() fuse: support idmapped ->rename op fuse: support idmapped ->set_acl fuse: drop idmap argument from __fuse_get_acl fuse: support idmapped ->setattr op fuse: support idmapped ->permission inode op fuse: support idmapped getattr inode op fuse: support idmap for mkdir/mknod/symlink/create/tmpfile fuse: support idmapped FUSE_EXT_GROUPS fuse: add an idmap argument to fuse_simple_request ...