kernel/linux.git/fs/fuse, branch v6.18.21

writeback: don't block sync for filesystems with no data integrity guarantees

2026-04-02T11:23:20+00:00

commit 76f9377cd2ab7a9220c25d33940d9ca20d368172 upstream. Add a SB_I_NO_DATA_INTEGRITY superblock flag for filesystems that cannot guarantee data persistence on sync (eg fuse). For superblocks with this flag set, sync kicks off writeback of dirty inodes but does not wait for the flusher threads to complete the writeback. This replaces the per-inode AS_NO_DATA_INTEGRITY mapping flag added in commit f9a49aa302a0 ("fs/writeback: skip AS_NO_DATA_INTEGRITY mappings in wait_sb_inodes()"). The flag belongs at the superblock level because data integrity is a filesystem-wide property, not a per-inode one. Having this flag at the superblock level also allows us to skip having to iterate every dirty inode in wait_sb_inodes() only to skip each inode individually. Prior to this commit, mappings with no data integrity guarantees skipped waiting on writeback completion but still waited on the flusher threads to finish initiating the writeback. Waiting on the flusher threads is unnecessary. This commit kicks off writeback but does not wait on the flusher threads. This change properly addresses a recent report [1] for a suspend-to-RAM hang seen on fuse-overlayfs that was caused by waiting on the flusher threads to finish: Workqueue: pm_fs_sync pm_fs_sync_work_fn Call Trace: __schedule+0x457/0x1720 schedule+0x27/0xd0 wb_wait_for_completion+0x97/0xe0 sync_inodes_sb+0xf8/0x2e0 __iterate_supers+0xdc/0x160 ksys_sync+0x43/0xb0 pm_fs_sync_work_fn+0x17/0xa0 process_one_work+0x193/0x350 worker_thread+0x1a1/0x310 kthread+0xfc/0x240 ret_from_fork+0x243/0x280 ret_from_fork_asm+0x1a/0x30 On fuse this is problematic because there are paths that may cause the flusher thread to block (eg if systemd freezes the user session cgroups first, which freezes the fuse daemon, before invoking the kernel suspend. The kernel suspend triggers ->write_node() which on fuse issues a synchronous setattr request, which cannot be processed since the daemon is frozen. Or if the daemon is buggy and cannot properly complete writeback, initiating writeback on a dirty folio already under writeback leads to writeback_get_folio() -> folio_prepare_writeback() -> unconditional wait on writeback to finish, which will cause a hang). This commit restores fuse to its prior behavior before tmp folios were removed, where sync was essentially a no-op. [1] https://lore.kernel.org/linux-fsdevel/CAJnrk1a-asuvfrbKXbEwwDSctvemF+6zfhdnuzO65Pt8HsFSRw@mail.gmail.com/T/#m632c4648e9cafc4239299887109ebd880ac6c5c1 Fixes: 0c58a97f919c ("fuse: remove tmp folio for writebacks and internal rb tree") Reported-by: John Cc: stable@vger.kernel.org Signed-off-by: Joanne Koong Link: https://patch.msgid.link/20260320005145.2483161-2-joannelkoong@gmail.com Reviewed-by: Jan Kara Reviewed-by: David Hildenbrand (Arm) Signed-off-by: Christian Brauner Signed-off-by: Greg Kroah-Hartman

fs/writeback: skip AS_NO_DATA_INTEGRITY mappings in wait_sb_inodes()

2026-01-30T09:32:15+00:00

commit f9a49aa302a05e91ca01f69031cb79a0ea33031f upstream. Above the while() loop in wait_sb_inodes(), we document that we must wait for all pages under writeback for data integrity. Consequently, if a mapping, like fuse, traditionally does not have data integrity semantics, there is no need to wait at all; we can simply skip these inodes. This restores fuse back to prior behavior where syncs are no-ops. This fixes a user regression where if a system is running a faulty fuse server that does not reply to issued write requests, this causes wait_sb_inodes() to wait forever. Link: https://lkml.kernel.org/r/20260105211737.4105620-2-joannelkoong@gmail.com Fixes: 0c58a97f919c ("fuse: remove tmp folio for writebacks and internal rb tree") Signed-off-by: Joanne Koong Reported-by: Athul Krishna Reported-by: J. Neuschäfer Reviewed-by: Bernd Schubert Tested-by: J. Neuschäfer Cc: Alexander Viro Cc: Bernd Schubert Cc: Bonaccorso Salvatore Cc: Christian Brauner Cc: David Hildenbrand Cc: Jan Kara Cc: "Liam R. Howlett" Cc: Lorenzo Stoakes Cc: "Matthew Wilcox (Oracle)" Cc: Michal Hocko Cc: Mike Rapoport Cc: Miklos Szeredi Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

fuse: missing copy_finish in fuse-over-io-uring argument copies

2026-01-02T11:57:31+00:00

commit 6e0d7f7f4a43ac8868e98c87ecf48805aa8c24dd upstream. Fix a possible reference count leak of payload pages during fuse argument copies. [Joanne: simplified error cleanup] Fixes: c090c8abae4b ("fuse: Add io-uring sqe commit and fetch support") Cc: stable@vger.kernel.org # v6.14 Signed-off-by: Cheng Ding Signed-off-by: Bernd Schubert Reviewed-by: Joanne Koong Signed-off-by: Miklos Szeredi Signed-off-by: Greg Kroah-Hartman

fuse: fix readahead reclaim deadlock

2026-01-02T11:57:31+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: fix io-uring list corruption for terminated non-committed requests

2026-01-02T11:57:31+00:00

commit 95c39eef7c2b666026c69ab5b30471da94ea2874 upstream. When a request is terminated before it has been committed, the request is not removed from the queue's list. This leaves a dangling list entry that leads to list corruption and use-after-free issues. Remove the request from the queue's list for terminated non-committed requests. Signed-off-by: Joanne Koong Fixes: c090c8abae4b ("fuse: Add io-uring sqe commit and fetch support") Cc: stable@vger.kernel.org Reviewed-by: Bernd Schubert Signed-off-by: Miklos Szeredi Signed-off-by: Greg Kroah-Hartman

fuse: Invalidate the page cache after FOPEN_DIRECT_IO write

2026-01-02T11:57:01+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

2026-01-02T11:57:01+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_ctl_add_conn(): fix nlink breakage in case of early failure

2025-12-18T13:03:02+00:00

[ Upstream commit c460192aae197df1b4db1dca493c35ad529f1b64 ] fuse_ctl_remove_conn() used to decrement the link count of root manually; that got subsumed by simple_recursive_removal(), but in case when subdirectory creation has failed the latter won't get called. Just move the modification of parent's link count into fuse_ctl_add_dentry() to keep the things simple. Allows to get rid of the nlink argument as well... Fixes: fcaac5b42768 "fuse_ctl: use simple_recursive_removal()" Acked-by: Miklos Szeredi Signed-off-by: Al Viro Signed-off-by: Sasha Levin

virtio-fs: fix incorrect check for fsvq->kobj

2025-11-05T13:00:16+00:00

In virtio_fs_add_queues_sysfs(), the code incorrectly checks fs->mqs_kobj after calling kobject_create_and_add(). Change the check to fsvq->kobj (fs->mqs_kobj -> fsvq->kobj) to ensure the per-queue kobject is successfully created. Fixes: 87cbdc396a31 ("virtio_fs: add sysfs entries for queue information") Signed-off-by: Alok Tiwari Link: https://patch.msgid.link/20251027104658.1668537-1-alok.a.tiwari@oracle.com Reviewed-by: Stefan Hajnoczi Signed-off-by: Christian Brauner

Revert "fs: make vfs_fileattr_[get|set] return -EOPNOTSUPP"

2025-10-10T11:44:03+00:00

This reverts commit 474b155adf3927d2c944423045757b54aa1ca4de. This patch caused regression in ioctl_setflags(). Underlying filesystems use EOPNOTSUPP to indicate that flag is not supported. This error is also gets converted in ioctl_setflags(). Therefore, for unsupported flags error changed from EOPNOSUPP to ENOIOCTLCMD. Link: https://lore.kernel.org/linux-xfs/a622643f-1585-40b0-9441-cf7ece176e83@kernel.org/ Signed-off-by: Andrey Albershteyn Signed-off-by: Christian Brauner