kernel/linux.git/fs/fs-writeback.c, branch v7.0-rc7

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

2026-03-20T13:18:56+00:00

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

fs: clear I_DIRTY_TIME in sync_lazytime

2026-03-17T14:12:15+00:00

For file systems implementing ->sync_lazytime, I_DIRTY_TIME fails to get cleared in sync_lazytime, and might cause additional calls to sync_lazytime during inode deactivation. Use the same pattern as in __mark_inode_dirty to clear the flag under the inode lock. Fixes: 5cf06ea56ee6 ("fs: add a ->sync_lazytime method") Signed-off-by: Christoph Hellwig Link: https://patch.msgid.link/20260317134409.1691317-1-hch@lst.de Signed-off-by: Christian Brauner

Merge tag 'vfs-7.0-rc2.fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

2026-02-25T18:34:23+00:00

Pull vfs fixes from Christian Brauner: - Fix an uninitialized variable in file_getattr(). The flags_valid field wasn't initialized before calling vfs_fileattr_get(), triggering KMSAN uninit-value reports in fuse - Fix writeback wakeup and logging timeouts when DETECT_HUNG_TASK is not enabled. sysctl_hung_task_timeout_secs is 0 in that case causing spurious "waiting for writeback completion for more than 1 seconds" warnings - Fix a null-ptr-deref in do_statmount() when the mount is internal - Add missing kernel-doc description for the @private parameter in iomap_readahead() - Fix mount namespace creation to hold namespace_sem across the mount copy in create_new_namespace(). The previous drop-and-reacquire pattern was fragile and failed to clean up mount propagation links if the real rootfs was a shared or dependent mount - Fix /proc mount iteration where m->index wasn't updated when m->show() overflows, causing a restart to repeatedly show the same mount entry in a rapidly expanding mount table - Return EFSCORRUPTED instead of ENOSPC in minix_new_inode() when the inode number is out of range - Fix unshare(2) when CLONE_NEWNS is set and current->fs isn't shared. copy_mnt_ns() received the live fs_struct so if a subsequent namespace creation failed the rollback would leave pwd and root pointing to detached mounts. Always allocate a new fs_struct when CLONE_NEWNS is requested - fserror bug fixes: - Remove the unused fsnotify_sb_error() helper now that all callers have been converted to fserror_report_metadata - Fix a lockdep splat in fserror_report() where igrab() takes inode::i_lock which can be held in IRQ context. Replace igrab() with a direct i_count bump since filesystems should not report inodes that are about to be freed or not yet exposed - Handle error pointer in procfs for try_lookup_noperm() - Fix an integer overflow in ep_loop_check_proc() where recursive calls returning INT_MAX would overflow when +1 is added, breaking the recursion depth check - Fix a misleading break in pidfs * tag 'vfs-7.0-rc2.fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: pidfs: avoid misleading break eventpoll: Fix integer overflow in ep_loop_check_proc() proc: Fix pointer error dereference fserror: fix lockdep complaint when igrabbing inode fsnotify: drop unused helper unshare: fix unshare_fs() handling minix: Correct errno in minix_new_inode namespace: fix proc mount iteration mount: hold namespace_sem across copy in create_new_namespace() iomap: Describe @private in iomap_readahead() statmount: Fix the null-ptr-deref in do_statmount() writeback: Fix wakeup and logging timeouts for !DETECT_HUNG_TASK fs: init flags_valid before calling vfs_fileattr_get

Convert 'alloc_flex' family to use the new default GFP_KERNEL argument

2026-02-22T01:09:51+00:00

This is the exact same thing as the 'alloc_obj()' version, only much smaller because there are a lot fewer users of the *alloc_flex() interface. As with alloc_obj() version, this was done entirely with mindless brute force, using the same script, except using 'flex' in the pattern rather than 'objs*'. Signed-off-by: Linus Torvalds

treewide: Replace kmalloc with kmalloc_obj for non-scalar types

2026-02-21T09:02:28+00:00

This is the result of running the Coccinelle script from scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to avoid scalar types (which need careful case-by-case checking), and instead replace kmalloc-family calls that allocate struct or union object instances: Single allocations: kmalloc(sizeof(TYPE), ...) are replaced with: kmalloc_obj(TYPE, ...) Array allocations: kmalloc_array(COUNT, sizeof(TYPE), ...) are replaced with: kmalloc_objs(TYPE, COUNT, ...) Flex array allocations: kmalloc(struct_size(PTR, FAM, COUNT), ...) are replaced with: kmalloc_flex(*PTR, FAM, COUNT, ...) (where TYPE may also be *VAR) The resulting allocations no longer return "void *", instead returning "TYPE *". Signed-off-by: Kees Cook

writeback: Fix wakeup and logging timeouts for !DETECT_HUNG_TASK

2026-02-14T12:17:46+00:00

Recent changes of fs-writeback cause such warnings if DETECT_HUNG_TASK is not enabled: INFO: The task sync:1342 has been waiting for writeback completion for more than 1 seconds. The reason is sysctl_hung_task_timeout_secs is 0 when DETECT_HUNG_TASK is not enabled, then it causes the warning message even if the writeback lasts for only one second. Guard the wakeup and logging with "#ifdef CONFIG_DETECT_HUNG_TASK" can eliminate the warning messages. But on the other hand, it is possible that sysctl_hung_task_timeout_secs be also 0 when DETECT_HUNG_TASK is enabled. So let's just check the value of sysctl_hung_task_timeout_secs to decide whether do wakeup and logging. Fixes: 1888635532fb ("writeback: Wake up waiting tasks when finishing the writeback of a chunk.") Fixes: d6e621590764 ("writeback: Add logging for slow writeback (exceeds sysctl_hung_task_timeout_secs)") Signed-off-by: Huacai Chen Link: https://patch.msgid.link/20260203094014.2273240-1-chenhuacai@loongson.cn Reviewed-by: Jan Kara Signed-off-by: Christian Brauner

Merge tag 'cgroup-for-6.20' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

2026-02-11T21:20:50+00:00

Pull cgroup updates from Tejun Heo: - cpuset changes: - Continue separating v1 and v2 implementations by moving more v1-specific logic into cpuset-v1.c - Improve partition handling. Sibling partitions are no longer invalidated on cpuset.cpus conflict, cpuset.cpus changes no longer fail in v2, and effective_xcpus computation is made consistent - Fix partition effective CPUs overlap that caused a warning on cpuset removal when sibling partitions shared CPUs - Increase the maximum cgroup subsystem count from 16 to 32 to accommodate future subsystem additions - Misc cleanups and selftest improvements including switching to css_is_online() helper, removing dead code and stale documentation references, using lockdep_assert_cpuset_lock_held() consistently, and adding polling helpers for asynchronously updated cgroup statistics * tag 'cgroup-for-6.20' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (21 commits) cpuset: fix overlap of partition effective CPUs cgroup: increase maximum subsystem count from 16 to 32 cgroup: Remove stale cpu.rt.max reference from documentation cpuset: replace direct lockdep_assert_held() with lockdep_assert_cpuset_lock_held() cgroup/cpuset: Move the v1 empty cpus/mems check to cpuset1_validate_change() cgroup/cpuset: Don't invalidate sibling partitions on cpuset.cpus conflict cgroup/cpuset: Don't fail cpuset.cpus change in v2 cgroup/cpuset: Consistently compute effective_xcpus in update_cpumasks_hier() cgroup/cpuset: Streamline rm_siblings_excl_cpus() cpuset: remove dead code in cpuset-v1.c cpuset: remove v1-specific code from generate_sched_domains cpuset: separate generate_sched_domains for v1 and v2 cpuset: move update_domain_attr_tree to cpuset_v1.c cpuset: add cpuset1_init helper for v1 initialization cpuset: add cpuset1_online_css helper for v1-specific operations cpuset: add lockdep_assert_cpuset_lock_held helper cpuset: Remove unnecessary checks in rebuild_sched_domains_locked cgroup: switch to css_is_online() helper selftests: cgroup: Replace sleep with cg_read_key_long_poll() for waiting on nr_dying_descendants selftests: cgroup: make test_memcg_sock robust against delayed sock stats ...

Merge tag 'vfs-7.0-rc1.nonblocking_timestamps' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

2026-02-09T19:25:01+00:00

Pull vfs timestamp updates from Christian Brauner: "This contains the changes to support non-blocking timestamp updates. Since commit 66fa3cedf16a ("fs: Add async write file modification handling") file_update_time_flags() unconditionally returns -EAGAIN when any timestamp needs updating and IOCB_NOWAIT is set. This makes non-blocking direct writes impossible on file systems with granular enough timestamps, which in practice means all of them. This reworks the timestamp update path to propagate IOCB_NOWAIT through ->update_time so that file systems which can update timestamps without blocking are no longer penalized. With that groundwork in place, the core change passes IOCB_NOWAIT into ->update_time and returns -EAGAIN only when the file system indicates it would block. XFS implements non-blocking timestamp updates by using the new ->sync_lazytime and open-coding generic_update_time without the S_NOWAIT check, since the lazytime path through the generic helpers can never block in XFS" * tag 'vfs-7.0-rc1.nonblocking_timestamps' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: xfs: enable non-blocking timestamp updates xfs: implement ->sync_lazytime fs: refactor file_update_time_flags fs: add support for non-blocking timestamp updates fs: add a ->sync_lazytime method fs: factor out a sync_lazytime helper fs: refactor ->update_time handling fat: cleanup the flags for fat_truncate_time nfs: split nfs_update_timestamps fs: allow error returns from generic_update_time fs: remove inode_update_time

Merge tag 'vfs-6.19-rc8.fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

2026-01-26T17:30:48+00:00

Pull vfs fixes from Christian Brauner: - Fix the the buggy conversion of fuse_reverse_inval_entry() introduced during the creation rework - Disallow nfs delegation requests for directories by setting simple_nosetlease() - Require an opt-in for getting readdir flag bits outside of S_DT_MASK set in d_type - Fix scheduling delayed writeback work by only scheduling when the dirty time expiry interval is non-zero and cancel the delayed work if the interval is set to zero - Use rounded_jiffies_interval for dirty time work - Check the return value of sb_set_blocksize() for romfs - Wait for batched folios to be stable in __iomap_get_folio() - Use private naming for fuse hash size - Fix the stale dentry cleanup to prevent a race that causes a UAF * tag 'vfs-6.19-rc8.fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: vfs: document d_dispose_if_unused() fuse: shrink once after all buckets have been scanned fuse: clean up fuse_dentry_tree_work() fuse: add need_resched() before unlocking bucket fuse: make sure dentry is evicted if stale fuse: fix race when disposing stale dentries fuse: use private naming for fuse hash size writeback: use round_jiffies_relative for dirtytime_work iomap: wait for batched folios to be stable in __iomap_get_folio romfs: check sb_set_blocksize() return value docs: clarify that dirtytime_expire_seconds=0 disables writeback writeback: fix 100% CPU usage when dirtytime_expire_interval is 0 readdir: require opt-in for d_type flags vboxsf: don't allow delegations to be set on directories ceph: don't allow delegations to be set on directories gfs2: don't allow delegations to be set on directories 9p: don't allow delegations to be set on directories smb/client: properly disallow delegations on directories nfs: properly disallow delegation requests on directories fuse: fix conversion of fuse_reverse_inval_entry() to start_removing()

fs/writeback: skip AS_NO_DATA_INTEGRITY mappings in wait_sb_inodes()

2026-01-19T20:30:01+00:00

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