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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:
<TASK>
__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
</TASK>
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 <therealgraysky@proton.me>
Cc: stable@vger.kernel.org
Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Link: https://patch.msgid.link/20260320005145.2483161-2-joannelkoong@gmail.com
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: David Hildenbrand (Arm) <david@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
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
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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
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
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Link: https://patch.msgid.link/20251104-work-guards-v1-1-5108ac78a171@kernel.org
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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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 <brauner@kernel.org>
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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 <brauner@kernel.org>
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