kernel/linux.git/include/linux/fs, branch v6.19.11

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

2026-04-02T11:25:43+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

Merge tag 'vfs-6.19-rc1.guards' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

2025-12-01T22:39:03+00:00

Pull superblock lock guard updates from Christian Brauner: "This starts the work of introducing guards for superblock related locks. Introduce super_write_guard for scoped superblock write protection. This provides a guard-based alternative to the manual sb_start_write() and sb_end_write() pattern, allowing the compiler to automatically handle the cleanup" * tag 'vfs-6.19-rc1.guards' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: xfs: use super write guard in xfs_file_ioctl() open: use super write guard in do_ftruncate() btrfs: use super write guard in relocating_repair_kthread() ext4: use super write guard in write_mmp_block() btrfs: use super write guard in sb_start_write() btrfs: use super write guard btrfs_run_defrag_inode() btrfs: use super write guard in btrfs_reclaim_bgs_work() fs: add super_write_guard

Merge tag 'vfs-6.19-rc1.fs_header' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

2025-12-01T22:18:01+00:00

Pull fs header updates from Christian Brauner: "This contains initial work to start splitting up fs.h. Begin the long-overdue work of splitting up the monolithic fs.h header. The header has grown to over 3000 lines and includes types and functions for many different subsystems, making it difficult to navigate and causing excessive compilation dependencies. This series introduces new focused headers for superblock-related code: - Rename fs_types.h to fs_dirent.h to better reflect its actual content (directory entry types) - Add fs/super_types.h containing superblock type definitions - Add fs/super.h containing superblock function declarations This is the first step in a longer effort to modularize the VFS headers. Cleanups: - Inode Field Layout Optimization (Mateusz Guzik) Move inode fields used during fast path lookup closer together to improve cache locality during path resolution. - current_umask() Optimization (Mateusz Guzik) Inline current_umask() and move it to fs_struct.h. This improves performance by avoiding function call overhead for this frequently-used function, and places it in a more appropriate header since it operates on fs_struct" * tag 'vfs-6.19-rc1.fs_header' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: fs: move inode fields used during fast path lookup closer together fs: inline current_umask() and move it to fs_struct.h fs: add fs/super.h header fs: add fs/super_types.h header fs: rename fs_types.h to fs_dirent.h

fs: add super_write_guard

2025-11-05T21:52:15+00:00

Link: https://patch.msgid.link/20251104-work-guards-v1-1-5108ac78a171@kernel.org Reviewed-by: Jan Kara Signed-off-by: Christian Brauner

fs: add fs/super.h header

2025-11-05T21:51:21+00:00

Split out super block associated functions into a separate header. Link: https://patch.msgid.link/20251104-work-fs-header-v1-3-fb39a2efe39e@kernel.org Signed-off-by: Christian Brauner

fs: add fs/super_types.h header

2025-11-05T21:47:52+00:00

Split out super block associated structures into a separate header. Link: https://patch.msgid.link/20251104-work-fs-header-v1-2-fb39a2efe39e@kernel.org Signed-off-by: Christian Brauner