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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull vfs writeback updates from Christian Brauner:
"This contains work adressing lockups reported by users when a systemd
unit reading lots of files from a filesystem mounted with the lazytime
mount option exits.
With the lazytime mount option enabled we can be switching many dirty
inodes on cgroup exit to the parent cgroup. The numbers observed in
practice when systemd slice of a large cron job exits can easily reach
hundreds of thousands or millions.
The logic in inode_do_switch_wbs() which sorts the inode into
appropriate place in b_dirty list of the target wb however has linear
complexity in the number of dirty inodes thus overall time complexity
of switching all the inodes is quadratic leading to workers being
pegged for hours consuming 100% of the CPU and switching inodes to the
parent wb.
Simple reproducer of the issue:
FILES=10000
# Filesystem mounted with lazytime mount option
MNT=/mnt/
echo "Creating files and switching timestamps"
for (( j = 0; j < 50; j ++ )); do
mkdir $MNT/dir$j
for (( i = 0; i < $FILES; i++ )); do
echo "foo" >$MNT/dir$j/file$i
done
touch -a -t 202501010000 $MNT/dir$j/file*
done
wait
echo "Syncing and flushing"
sync
echo 3 >/proc/sys/vm/drop_caches
echo "Reading all files from a cgroup"
mkdir /sys/fs/cgroup/unified/mycg1 || exit
echo $$ >/sys/fs/cgroup/unified/mycg1/cgroup.procs || exit
for (( j = 0; j < 50; j ++ )); do
cat /mnt/dir$j/file* >/dev/null &
done
wait
echo "Switching wbs"
# Now rmdir the cgroup after the script exits
This can be solved by:
- Avoiding contention on the wb->list_lock when switching inodes by
running a single work item per wb and managing a queue of items
switching to the wb
- Allowing rescheduling when switching inodes over to a different
cgroup to avoid softlockups
- Maintaining the b_dirty list ordering instead of sorting it"
* tag 'vfs-6.18-rc1.writeback' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
writeback: Add tracepoint to track pending inode switches
writeback: Avoid excessively long inode switching times
writeback: Avoid softlockup when switching many inodes
writeback: Avoid contention on wb->list_lock when switching inodes
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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull vfs workqueue updates from Christian Brauner:
"This contains various workqueue changes affecting the filesystem
layer.
Currently if a user enqueue a work item using schedule_delayed_work()
the used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use
WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies
to schedule_work() that is using system_wq and queue_work(), that
makes use again of WORK_CPU_UNBOUND.
This replaces the use of system_wq and system_unbound_wq. system_wq is
a per-CPU workqueue which isn't very obvious from the name and
system_unbound_wq is to be used when locality is not required.
So this renames system_wq to system_percpu_wq, and system_unbound_wq
to system_dfl_wq.
This also adds a new WQ_PERCPU flag to allow the fs subsystem users to
explicitly request the use of per-CPU behavior. Both WQ_UNBOUND and
WQ_PERCPU flags coexist for one release cycle to allow callers to
transition their calls. WQ_UNBOUND will be removed in a next release
cycle"
* tag 'vfs-6.18-rc1.workqueue' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
fs: WQ_PERCPU added to alloc_workqueue users
fs: replace use of system_wq with system_percpu_wq
fs: replace use of system_unbound_wq with system_dfl_wq
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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull vfs inode updates from Christian Brauner:
"This contains a series I originally wrote and that Eric brought over
the finish line. It moves out the i_crypt_info and i_verity_info
pointers out of 'struct inode' and into the fs-specific part of the
inode.
So now the few filesytems that actually make use of this pay the price
in their own private inode storage instead of forcing it upon every
user of struct inode.
The pointer for the crypt and verity info is simply found by storing
an offset to its address in struct fsverity_operations and struct
fscrypt_operations. This shrinks struct inode by 16 bytes.
I hope to move a lot more out of it in the future so that struct inode
becomes really just about very core stuff that we need, much like
struct dentry and struct file, instead of the dumping ground it has
become over the years.
On top of this are a various changes associated with the ongoing inode
lifetime handling rework that multiple people are pushing forward:
- Stop accessing inode->i_count directly in f2fs and gfs2. They
simply should use the __iget() and iput() helpers
- Make the i_state flags an enum
- Rework the iput() logic
Currently, if we are the last iput, and we have the I_DIRTY_TIME
bit set, we will grab a reference on the inode again and then mark
it dirty and then redo the put. This is to make sure we delay the
time update for as long as possible
We can rework this logic to simply dec i_count if it is not 1, and
if it is do the time update while still holding the i_count
reference
Then we can replace the atomic_dec_and_lock with locking the
->i_lock and doing atomic_dec_and_test, since we did the
atomic_add_unless above
- Add an icount_read() helper and convert everyone that accesses
inode->i_count directly for this purpose to use the helper
- Expand dump_inode() to dump more information about an inode helping
in debugging
- Add some might_sleep() annotations to iput() and associated
helpers"
* tag 'vfs-6.18-rc1.inode' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
fs: add might_sleep() annotation to iput() and more
fs: expand dump_inode()
inode: fix whitespace issues
fs: add an icount_read helper
fs: rework iput logic
fs: make the i_state flags an enum
fs: stop accessing ->i_count directly in f2fs and gfs2
fsverity: check IS_VERITY() in fsverity_cleanup_inode()
fs: remove inode::i_verity_info
btrfs: move verity info pointer to fs-specific part of inode
f2fs: move verity info pointer to fs-specific part of inode
ext4: move verity info pointer to fs-specific part of inode
fsverity: add support for info in fs-specific part of inode
fs: remove inode::i_crypt_info
ceph: move crypt info pointer to fs-specific part of inode
ubifs: move crypt info pointer to fs-specific part of inode
f2fs: move crypt info pointer to fs-specific part of inode
ext4: move crypt info pointer to fs-specific part of inode
fscrypt: add support for info in fs-specific part of inode
fscrypt: replace raw loads of info pointer with helper function
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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull misc vfs updates from Christian Brauner:
"This contains the usual selections of misc updates for this cycle.
Features:
- Add "initramfs_options" parameter to set initramfs mount options.
This allows to add specific mount options to the rootfs to e.g.,
limit the memory size
- Add RWF_NOSIGNAL flag for pwritev2()
Add RWF_NOSIGNAL flag for pwritev2. This flag prevents the SIGPIPE
signal from being raised when writing on disconnected pipes or
sockets. The flag is handled directly by the pipe filesystem and
converted to the existing MSG_NOSIGNAL flag for sockets
- Allow to pass pid namespace as procfs mount option
Ever since the introduction of pid namespaces, procfs has had very
implicit behaviour surrounding them (the pidns used by a procfs
mount is auto-selected based on the mounting process's active
pidns, and the pidns itself is basically hidden once the mount has
been constructed)
This implicit behaviour has historically meant that userspace was
required to do some special dances in order to configure the pidns
of a procfs mount as desired. Examples include:
* In order to bypass the mnt_too_revealing() check, Kubernetes
creates a procfs mount from an empty pidns so that user
namespaced containers can be nested (without this, the nested
containers would fail to mount procfs)
But this requires forking off a helper process because you cannot
just one-shot this using mount(2)
* Container runtimes in general need to fork into a container
before configuring its mounts, which can lead to security issues
in the case of shared-pidns containers (a privileged process in
the pidns can interact with your container runtime process)
While SUID_DUMP_DISABLE and user namespaces make this less of an
issue, the strict need for this due to a minor uAPI wart is kind
of unfortunate
Things would be much easier if there was a way for userspace to
just specify the pidns they want. So this pull request contains
changes to implement a new "pidns" argument which can be set
using fsconfig(2):
fsconfig(procfd, FSCONFIG_SET_FD, "pidns", NULL, nsfd);
fsconfig(procfd, FSCONFIG_SET_STRING, "pidns", "/proc/self/ns/pid", 0);
or classic mount(2) / mount(8):
// mount -t proc -o pidns=/proc/self/ns/pid proc /tmp/proc
mount("proc", "/tmp/proc", "proc", MS_..., "pidns=/proc/self/ns/pid");
Cleanups:
- Remove the last references to EXPORT_OP_ASYNC_LOCK
- Make file_remove_privs_flags() static
- Remove redundant __GFP_NOWARN when GFP_NOWAIT is used
- Use try_cmpxchg() in start_dir_add()
- Use try_cmpxchg() in sb_init_done_wq()
- Replace offsetof() with struct_size() in ioctl_file_dedupe_range()
- Remove vfs_ioctl() export
- Replace rwlock() with spinlock in epoll code as rwlock causes
priority inversion on preempt rt kernels
- Make ns_entries in fs/proc/namespaces const
- Use a switch() statement() in init_special_inode() just like we do
in may_open()
- Use struct_size() in dir_add() in the initramfs code
- Use str_plural() in rd_load_image()
- Replace strcpy() with strscpy() in find_link()
- Rename generic_delete_inode() to inode_just_drop() and
generic_drop_inode() to inode_generic_drop()
- Remove unused arguments from fcntl_{g,s}et_rw_hint()
Fixes:
- Document @name parameter for name_contains_dotdot() helper
- Fix spelling mistake
- Always return zero from replace_fd() instead of the file descriptor
number
- Limit the size for copy_file_range() in compat mode to prevent a
signed overflow
- Fix debugfs mount options not being applied
- Verify the inode mode when loading it from disk in minixfs
- Verify the inode mode when loading it from disk in cramfs
- Don't trigger automounts with RESOLVE_NO_XDEV
If openat2() was called with RESOLVE_NO_XDEV it didn't traverse
through automounts, but could still trigger them
- Add FL_RECLAIM flag to show_fl_flags() macro so it appears in
tracepoints
- Fix unused variable warning in rd_load_image() on s390
- Make INITRAMFS_PRESERVE_MTIME depend on BLK_DEV_INITRD
- Use ns_capable_noaudit() when determining net sysctl permissions
- Don't call path_put() under namespace semaphore in listmount() and
statmount()"
* tag 'vfs-6.18-rc1.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (38 commits)
fcntl: trim arguments
listmount: don't call path_put() under namespace semaphore
statmount: don't call path_put() under namespace semaphore
pid: use ns_capable_noaudit() when determining net sysctl permissions
fs: rename generic_delete_inode() and generic_drop_inode()
init: INITRAMFS_PRESERVE_MTIME should depend on BLK_DEV_INITRD
initramfs: Replace strcpy() with strscpy() in find_link()
initrd: Use str_plural() in rd_load_image()
initramfs: Use struct_size() helper to improve dir_add()
initrd: Fix unused variable warning in rd_load_image() on s390
fs: use the switch statement in init_special_inode()
fs/proc/namespaces: make ns_entries const
filelock: add FL_RECLAIM to show_fl_flags() macro
eventpoll: Replace rwlock with spinlock
selftests/proc: add tests for new pidns APIs
procfs: add "pidns" mount option
pidns: move is-ancestor logic to helper
openat2: don't trigger automounts with RESOLVE_NO_XDEV
namei: move cross-device check to __traverse_mounts
namei: remove LOOKUP_NO_XDEV check from handle_mounts
...
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Currently if a user enqueue a work item using schedule_delayed_work() the
used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use
WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies to
schedule_work() that is using system_wq and queue_work(), that makes use
again of WORK_CPU_UNBOUND.
This lack of consistentcy cannot be addressed without refactoring the API.
alloc_workqueue() treats all queues as per-CPU by default, while unbound
workqueues must opt-in via WQ_UNBOUND.
This default is suboptimal: most workloads benefit from unbound queues,
allowing the scheduler to place worker threads where they’re needed and
reducing noise when CPUs are isolated.
This patch adds a new WQ_PERCPU flag to all the fs subsystem users to
explicitly request the use of the per-CPU behavior. Both flags coexist
for one release cycle to allow callers to transition their calls.
Once migration is complete, WQ_UNBOUND can be removed and unbound will
become the implicit default.
With the introduction of the WQ_PERCPU flag (equivalent to !WQ_UNBOUND),
any alloc_workqueue() caller that doesn’t explicitly specify WQ_UNBOUND
must now use WQ_PERCPU.
All existing users have been updated accordingly.
Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
Link: https://lore.kernel.org/20250916082906.77439-4-marco.crivellari@suse.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Currently if a user enqueue a work item using schedule_delayed_work() the
used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use
WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies to
schedule_work() that is using system_wq and queue_work(), that makes use
again of WORK_CPU_UNBOUND.
This lack of consistentcy cannot be addressed without refactoring the API.
system_wq is a per-CPU worqueue, yet nothing in its name tells about that
CPU affinity constraint, which is very often not required by users.
Make it clear by adding a system_percpu_wq to all the fs subsystem.
The old wq will be kept for a few release cylces.
Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
Link: https://lore.kernel.org/20250916082906.77439-3-marco.crivellari@suse.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Add trace_inode_switch_wbs_queue tracepoint to allow insight into how
many inodes are queued to switch their bdi_writeback structure.
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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With lazytime mount option enabled we can be switching many dirty inodes
on cgroup exit to the parent cgroup. The numbers observed in practice
when systemd slice of a large cron job exits can easily reach hundreds
of thousands or millions. The logic in inode_do_switch_wbs() which sorts
the inode into appropriate place in b_dirty list of the target wb
however has linear complexity in the number of dirty inodes thus overall
time complexity of switching all the inodes is quadratic leading to
workers being pegged for hours consuming 100% of the CPU and switching
inodes to the parent wb.
Simple reproducer of the issue:
FILES=10000
# Filesystem mounted with lazytime mount option
MNT=/mnt/
echo "Creating files and switching timestamps"
for (( j = 0; j < 50; j ++ )); do
mkdir $MNT/dir$j
for (( i = 0; i < $FILES; i++ )); do
echo "foo" >$MNT/dir$j/file$i
done
touch -a -t 202501010000 $MNT/dir$j/file*
done
wait
echo "Syncing and flushing"
sync
echo 3 >/proc/sys/vm/drop_caches
echo "Reading all files from a cgroup"
mkdir /sys/fs/cgroup/unified/mycg1 || exit
echo $$ >/sys/fs/cgroup/unified/mycg1/cgroup.procs || exit
for (( j = 0; j < 50; j ++ )); do
cat /mnt/dir$j/file* >/dev/null &
done
wait
echo "Switching wbs"
# Now rmdir the cgroup after the script exits
We need to maintain b_dirty list ordering to keep writeback happy so
instead of sorting inode into appropriate place just append it at the
end of the list and clobber dirtied_time_when. This may result in inode
writeback starting later after cgroup switch however cgroup switches are
rare so it shouldn't matter much. Since the cgroup had write access to
the inode, there are no practical concerns of the possible DoS issues.
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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process_inode_switch_wbs_work() can be switching over 100 inodes to a
different cgroup. Since switching an inode requires counting all dirty &
under-writeback pages in the address space of each inode, this can take
a significant amount of time. Add a possibility to reschedule after
processing each inode to avoid softlockups.
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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There can be multiple inode switch works that are trying to switch
inodes to / from the same wb. This can happen in particular if some
cgroup exits which owns many (thousands) inodes and we need to switch
them all. In this case several inode_switch_wbs_work_fn() instances will
be just spinning on the same wb->list_lock while only one of them makes
forward progress. This wastes CPU cycles and quickly leads to softlockup
reports and unusable system.
Instead of running several inode_switch_wbs_work_fn() instances in
parallel switching to the same wb and contending on wb->list_lock, run
just one work item per wb and manage a queue of isw items switching to
this wb.
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jan Kara <jack@suse.cz>
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Instead of doing direct access to ->i_count, add a helper to handle
this. This will make it easier to convert i_count to a refcount later.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Link: https://lore.kernel.org/9bc62a84c6b9d6337781203f60837bd98fbc4a96.1756222464.git.josef@toxicpanda.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
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GFP_NOWAIT already includes __GFP_NOWARN, so let's remove
the redundant __GFP_NOWARN.
Signed-off-by: Qianfeng Rong <rongqianfeng@vivo.com>
Link: https://lore.kernel.org/20250803102243.623705-5-rongqianfeng@vivo.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
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An use-after-free issue occurred when __mark_inode_dirty() get the
bdi_writeback that was in the progress of switching.
CPU: 1 PID: 562 Comm: systemd-random- Not tainted 6.6.56-gb4403bd46a8e #1
......
pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : __mark_inode_dirty+0x124/0x418
lr : __mark_inode_dirty+0x118/0x418
sp : ffffffc08c9dbbc0
........
Call trace:
__mark_inode_dirty+0x124/0x418
generic_update_time+0x4c/0x60
file_modified+0xcc/0xd0
ext4_buffered_write_iter+0x58/0x124
ext4_file_write_iter+0x54/0x704
vfs_write+0x1c0/0x308
ksys_write+0x74/0x10c
__arm64_sys_write+0x1c/0x28
invoke_syscall+0x48/0x114
el0_svc_common.constprop.0+0xc0/0xe0
do_el0_svc+0x1c/0x28
el0_svc+0x40/0xe4
el0t_64_sync_handler+0x120/0x12c
el0t_64_sync+0x194/0x198
Root cause is:
systemd-random-seed kworker
----------------------------------------------------------------------
___mark_inode_dirty inode_switch_wbs_work_fn
spin_lock(&inode->i_lock);
inode_attach_wb
locked_inode_to_wb_and_lock_list
get inode->i_wb
spin_unlock(&inode->i_lock);
spin_lock(&wb->list_lock)
spin_lock(&inode->i_lock)
inode_io_list_move_locked
spin_unlock(&wb->list_lock)
spin_unlock(&inode->i_lock)
spin_lock(&old_wb->list_lock)
inode_do_switch_wbs
spin_lock(&inode->i_lock)
inode->i_wb = new_wb
spin_unlock(&inode->i_lock)
spin_unlock(&old_wb->list_lock)
wb_put_many(old_wb, nr_switched)
cgwb_release
old wb released
wb_wakeup_delayed() accesses wb,
then trigger the use-after-free
issue
Fix this race condition by holding inode spinlock until
wb_wakeup_delayed() finished.
Signed-off-by: Jiufei Xue <jiufei.xue@samsung.com>
Link: https://lore.kernel.org/20250728100715.3863241-1-jiufei.xue@samsung.com
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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The dirtytime_expire_interval belongs to fs/fs-writeback.c, move it to
fs/fs-writeback.c from /kernel/sysctl.c. And remove the useless extern
variable declaration and the function declaration from
include/linux/writeback.h
Signed-off-by: Kaixiong Yu <yukaixiong@huawei.com>
Reviewed-by: Kees Cook <kees@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Joel Granados <joel.granados@kernel.org>
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Christoph Hellwig <hch@lst.de> says:
This fixes one (of multiple) sparse warnings in fs-writeback.c, and
then reshuffles the code a bit that only the proper high level API
instead of low-level helpers is exported.
* patches from https://lore.kernel.org/r/20241112054403.1470586-1-hch@lst.de:
writeback: wbc_attach_fdatawrite_inode out of line
writeback: add a __releases annoation to wbc_attach_and_unlock_inode
Link: https://lore.kernel.org/r/20241112054403.1470586-1-hch@lst.de
Signed-off-by: Christian Brauner <brauner@kernel.org>
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This allows exporting this high-level interface only while keeping
wbc_attach_and_unlock_inode private in fs-writeback.c and unexporting
__inode_attach_wb.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20241112054403.1470586-3-hch@lst.de
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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This shuts up a sparse lock context tracking warning.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20241112054403.1470586-2-hch@lst.de
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Most of the callers of wbc_account_cgroup_owner() are converting a folio
to page before calling the function. wbc_account_cgroup_owner() is
converting the page back to a folio to call mem_cgroup_css_from_folio().
Convert wbc_account_cgroup_owner() to take a folio instead of a page,
and convert all callers to pass a folio directly except f2fs.
Convert the page to folio for all the callers from f2fs as they were the
only callers calling wbc_account_cgroup_owner() with a page. As f2fs is
already in the process of converting to folios, these call sites might
also soon be calling wbc_account_cgroup_owner() with a folio directly in
the future.
No functional changes. Only compile tested.
Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
Link: https://lore.kernel.org/r/20240926140121.203821-1-kernel@pankajraghav.com
Acked-by: David Sterba <dsterba@suse.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Port the __I_SYNC mechanism to use the new var event mechanism.
Link: https://lore.kernel.org/r/20240823-work-i_state-v3-3-5cd5fd207a57@kernel.org
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Most commonly neither I_LRU_ISOLATING nor I_SYNC are set, but the stock
kernel takes a back-to-back relock trip to check for them.
It probably can be avoided altogether, but for now massage things back
to just one lock acquire.
Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Link: https://lore.kernel.org/r/20240813143626.1573445-1-mjguzik@gmail.com
Reviewed-by: Zhihao Cheng <chengzhihao1@huawei.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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When deactivating any type of superblock, it had to wait for the in-flight
wb switches to be completed. wb switches are executed in inode_switch_wbs_work_fn()
which needs to acquire the wb_switch_rwsem and races against sync_inodes_sb().
If there are too much dirty data in the superblock, the waiting time may increase
significantly.
For superblocks without cgroup writeback such as tmpfs, they have nothing to
do with the wb swithes, so the flushing can be avoided.
Signed-off-by: Haifeng Xu <haifeng.xu@shopee.com>
Link: https://lore.kernel.org/r/20240726030525.180330-1-haifeng.xu@shopee.com
Reviewed-by: Jan Kara <jack@suse.cz>
Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
|
|
const qualify the struct ctl_table argument in the proc_handler function
signatures. This is a prerequisite to moving the static ctl_table
structs into .rodata data which will ensure that proc_handler function
pointers cannot be modified.
This patch has been generated by the following coccinelle script:
```
virtual patch
@r1@
identifier ctl, write, buffer, lenp, ppos;
identifier func !~ "appldata_(timer|interval)_handler|sched_(rt|rr)_handler|rds_tcp_skbuf_handler|proc_sctp_do_(hmac_alg|rto_min|rto_max|udp_port|alpha_beta|auth|probe_interval)";
@@
int func(
- struct ctl_table *ctl
+ const struct ctl_table *ctl
,int write, void *buffer, size_t *lenp, loff_t *ppos);
@r2@
identifier func, ctl, write, buffer, lenp, ppos;
@@
int func(
- struct ctl_table *ctl
+ const struct ctl_table *ctl
,int write, void *buffer, size_t *lenp, loff_t *ppos)
{ ... }
@r3@
identifier func;
@@
int func(
- struct ctl_table *
+ const struct ctl_table *
,int , void *, size_t *, loff_t *);
@r4@
identifier func, ctl;
@@
int func(
- struct ctl_table *ctl
+ const struct ctl_table *ctl
,int , void *, size_t *, loff_t *);
@r5@
identifier func, write, buffer, lenp, ppos;
@@
int func(
- struct ctl_table *
+ const struct ctl_table *
,int write, void *buffer, size_t *lenp, loff_t *ppos);
```
* Code formatting was adjusted in xfs_sysctl.c to comply with code
conventions. The xfs_stats_clear_proc_handler,
xfs_panic_mask_proc_handler and xfs_deprecated_dointvec_minmax where
adjusted.
* The ctl_table argument in proc_watchdog_common was const qualified.
This is called from a proc_handler itself and is calling back into
another proc_handler, making it necessary to change it as part of the
proc_handler migration.
Co-developed-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Co-developed-by: Joel Granados <j.granados@samsung.com>
Signed-off-by: Joel Granados <j.granados@samsung.com>
|
|
writeback_inodes_sb doesn't have return value, just remove unnecessary
return in it.
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Link: https://lore.kernel.org/r/20240228091958.288260-7-shikemeng@huaweicloud.com
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
|
|
Commit e8e8a0c6c9bfc ("writeback: move nr_pages == 0 logic to one
location") removed parameter nr_pages of __wakeup_flusher_threads_bdi
and we try to writeback all dirty pages in __wakeup_flusher_threads_bdi
now. Just correct stale comment.
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Link: https://lore.kernel.org/r/20240228091958.288260-6-shikemeng@huaweicloud.com
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
|
|
The dirtied_before is only used when b_io is not empty, so only calculate
when b_io is not empty.
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Link: https://lore.kernel.org/r/20240228091958.288260-5-shikemeng@huaweicloud.com
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
|
|
Remove unused parameter wb of finish_writeback_work.
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Link: https://lore.kernel.org/r/20240228091958.288260-4-shikemeng@huaweicloud.com
Reviewed-by: Tim Chen <tim.c.chen@linux.intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
|
|
For case there is no more inodes for IO in io list from last wb_writeback,
We may bail out early even there is inode in dirty list should be written
back. Only bail out when we queued once to avoid missing dirtied inode.
This is from code reading...
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Link: https://lore.kernel.org/r/20240228091958.288260-3-shikemeng@huaweicloud.com
Reviewed-by: Jan Kara <jack@suse.cz>
[brauner@kernel.org: fold in memory corruption fix from Jan in [1]]
Link: https://lore.kernel.org/r/20240405132346.bid7gibby3lxxhez@quack3 [1]
Signed-off-by: Christian Brauner <brauner@kernel.org>
|
|
In kupdate writeback, only expired inode (have been dirty for longer than
dirty_expire_interval) is supposed to be written back. However, kupdate
writeback will writeback non-expired inode left in b_io or b_more_io from
last wb_writeback. As a result, writeback will keep being triggered
unexpected when we keep dirtying pages even dirty memory is under
threshold and inode is not expired. To be more specific:
Assume dirty background threshold is > 1G and dirty_expire_centisecs is
> 60s. When we running fio -size=1G -invalidate=0 -ioengine=libaio
--time_based -runtime=60... (keep dirtying), the writeback will keep
being triggered as following:
wb_workfn
wb_do_writeback
wb_check_background_flush
/*
* Wb dirty background threshold starts at 0 if device was idle and
* grows up when bandwidth of wb is updated. So a background
* writeback is triggered.
*/
wb_over_bg_thresh
/*
* Dirtied inode will be written back and added to b_more_io list
* after slice used up (because we keep dirtying the inode).
*/
wb_writeback
Writeback is triggered per dirty_writeback_centisecs as following:
wb_workfn
wb_do_writeback
wb_check_old_data_flush
/*
* Write back inode left in b_io and b_more_io from last wb_writeback
* even the inode is non-expired and it will be added to b_more_io
* again as slice will be used up (because we keep dirtying the
* inode)
*/
wb_writeback
Fix this by moving non-expired inode to dirty list instead of more io
list for kupdate writeback in requeue_inode.
Test as following:
/* make it more easier to observe the issue */
echo 300000 > /proc/sys/vm/dirty_expire_centisecs
echo 100 > /proc/sys/vm/dirty_writeback_centisecs
/* create a idle device */
mkfs.ext4 -F /dev/vdb
mount /dev/vdb /bdi1/
/* run buffer write with fio */
fio -name test -filename=/bdi1/file -size=800M -ioengine=libaio -bs=4K \
-iodepth=1 -rw=write -direct=0 --time_based -runtime=60 -invalidate=0
Fio result before fix (run three tests):
1360MB/s
1329MB/s
1455MB/s
Fio result after fix (run three tests):
1737MB/s
1729MB/s
1789MB/s
Writeback for non-expired inode is gone as expeted. Observe this with trace
writeback_start and writeback_written as following:
echo 1 > /sys/kernel/debug/tracing/events/writeback/writeback_start/enab
echo 1 > /sys/kernel/debug/tracing/events/writeback/writeback_written/enable
cat /sys/kernel/tracing/trace_pipe
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Link: https://lore.kernel.org/r/20240228091958.288260-2-shikemeng@huaweicloud.com
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
|
|
The wb_wakeup_delayed is only used in fs-writeback.c. Move it to
fs-writeback.c after defination of wb_wakeup and make it static.
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Link: https://lore.kernel.org/r/20240118203339.764093-1-shikemeng@huaweicloud.com
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
|
|
Move the resource pinning-for-writeback from fscache code to netfslib code.
This is used to keep a cache backing object pinned whilst we have dirty
pages on the netfs inode in the pagecache such that VM writeback will be
able to reach it.
Whilst we're at it, switch the parameters of netfs_unpin_writeback() to
match ->write_inode() so that it can be used for that directly.
Note that this mechanism could be more generically useful than that for
network filesystems. Quite often they have to keep around other resources
(e.g. authentication tokens or network connections) until the writeback is
complete.
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
|
|
Pull misc vfs updates from Christian Brauner:
"This contains the usual miscellaneous features, cleanups, and fixes
for vfs and individual fses.
Features:
- Rename and export helpers that get write access to a mount. They
are used in overlayfs to get write access to the upper mount.
- Print the pretty name of the root device on boot failure. This
helps in scenarios where we would usually only print
"unknown-block(1,2)".
- Add an internal SB_I_NOUMASK flag. This is another part in the
endless POSIX ACL saga in a way.
When POSIX ACLs are enabled via SB_POSIXACL the vfs cannot strip
the umask because if the relevant inode has POSIX ACLs set it might
take the umask from there. But if the inode doesn't have any POSIX
ACLs set then we apply the umask in the filesytem itself. So we end
up with:
(1) no SB_POSIXACL -> strip umask in vfs
(2) SB_POSIXACL -> strip umask in filesystem
The umask semantics associated with SB_POSIXACL allowed filesystems
that don't even support POSIX ACLs at all to raise SB_POSIXACL
purely to avoid umask stripping. That specifically means NFS v4 and
Overlayfs. NFS v4 does it because it delegates this to the server
and Overlayfs because it needs to delegate umask stripping to the
upper filesystem, i.e., the filesystem used as the writable layer.
This went so far that SB_POSIXACL is raised eve on kernels that
don't even have POSIX ACL support at all.
Stop this blatant abuse and add SB_I_NOUMASK which is an internal
superblock flag that filesystems can raise to opt out of umask
handling. That should really only be the two mentioned above. It's
not that we want any filesystems to do this. Ideally we have all
umask handling always in the vfs.
- Make overlayfs use SB_I_NOUMASK too.
- Now that we have SB_I_NOUMASK, stop checking for SB_POSIXACL in
IS_POSIXACL() if the kernel doesn't have support for it. This is a
very old patch but it's only possible to do this now with the wider
cleanup that was done.
- Follow-up work on fake path handling from last cycle. Citing mostly
from Amir:
When overlayfs was first merged, overlayfs files of regular files
and directories, the ones that are installed in file table, had a
"fake" path, namely, f_path is the overlayfs path and f_inode is
the "real" inode on the underlying filesystem.
In v6.5, we took another small step by introducing of the
backing_file container and the file_real_path() helper. This change
allowed vfs and filesystem code to get the "real" path of an
overlayfs backing file. With this change, we were able to make
fsnotify work correctly and report events on the "real" filesystem
objects that were accessed via overlayfs.
This method works fine, but it still leaves the vfs vulnerable to
new code that is not aware of files with fake path. A recent
example is commit db1d1e8b9867 ("IMA: use vfs_getattr_nosec to get
the i_version"). This commit uses direct referencing to f_path in
IMA code that otherwise uses file_inode() and file_dentry() to
reference the filesystem objects that it is measuring.
This contains work to switch things around: instead of having
filesystem code opt-in to get the "real" path, have generic code
opt-in for the "fake" path in the few places that it is needed.
Is it far more likely that new filesystems code that does not use
the file_dentry() and file_real_path() helpers will end up causing
crashes or averting LSM/audit rules if we keep the "fake" path
exposed by default.
This change already makes file_dentry() moot, but for now we did
not change this helper just added a WARN_ON() in ovl_d_real() to
catch if we have made any wrong assumptions.
After the dust settles on this change, we can make file_dentry() a
plain accessor and we can drop the inode argument to ->d_real().
- Switch struct file to SLAB_TYPESAFE_BY_RCU. This looks like a small
change but it really isn't and I would like to see everyone on
their tippie toes for any possible bugs from this work.
Essentially we've been doing most of what SLAB_TYPESAFE_BY_RCU for
files since a very long time because of the nasty interactions
between the SCM_RIGHTS file descriptor garbage collection. So
extending it makes a lot of sense but it is a subtle change. There
are almost no places that fiddle with file rcu semantics directly
and the ones that did mess around with struct file internal under
rcu have been made to stop doing that because it really was always
dodgy.
I forgot to put in the link tag for this change and the discussion
in the commit so adding it into the merge message:
https://lore.kernel.org/r/20230926162228.68666-1-mjguzik@gmail.com
Cleanups:
- Various smaller pipe cleanups including the removal of a spin lock
that was only used to protect against writes without pipe_lock()
from O_NOTIFICATION_PIPE aka watch queues. As that was never
implemented remove the additional locking from pipe_write().
- Annotate struct watch_filter with the new __counted_by attribute.
- Clarify do_unlinkat() cleanup so that it doesn't look like an extra
iput() is done that would cause issues.
- Simplify file cleanup when the file has never been opened.
- Use module helper instead of open-coding it.
- Predict error unlikely for stale retry.
- Use WRITE_ONCE() for mount expiry field instead of just commenting
that one hopes the compiler doesn't get smart.
Fixes:
- Fix readahead on block devices.
- Fix writeback when layztime is enabled and inodes whose timestamp
is the only thing that changed reside on wb->b_dirty_time. This
caused excessively large zombie memory cgroup when lazytime was
enabled as such inodes weren't handled fast enough.
- Convert BUG_ON() to WARN_ON_ONCE() in open_last_lookups()"
* tag 'vfs-6.7.misc' of gitolite.kernel.org:pub/scm/linux/kernel/git/vfs/vfs: (26 commits)
file, i915: fix file reference for mmap_singleton()
vfs: Convert BUG_ON to WARN_ON_ONCE in open_last_lookups
writeback, cgroup: switch inodes with dirty timestamps to release dying cgwbs
chardev: Simplify usage of try_module_get()
ovl: rely on SB_I_NOUMASK
fs: fix umask on NFS with CONFIG_FS_POSIX_ACL=n
fs: store real path instead of fake path in backing file f_path
fs: create helper file_user_path() for user displayed mapped file path
fs: get mnt_writers count for an open backing file's real path
vfs: stop counting on gcc not messing with mnt_expiry_mark if not asked
vfs: predict the error in retry_estale as unlikely
backing file: free directly
vfs: fix readahead(2) on block devices
io_uring: use files_lookup_fd_locked()
file: convert to SLAB_TYPESAFE_BY_RCU
vfs: shave work on failed file open
fs: simplify misleading code to remove ambiguity regarding ihold()/iput()
watch_queue: Annotate struct watch_filter with __counted_by
fs/pipe: use spinlock in pipe_read() only if there is a watch_queue
fs/pipe: remove unnecessary spinlock from pipe_write()
...
|
|
The cgwb cleanup routine will try to release the dying cgwb by switching
the attached inodes. It fetches the attached inodes from wb->b_attached
list, omitting the fact that inodes only with dirty timestamps reside in
wb->b_dirty_time list, which is the case when lazytime is enabled. This
causes enormous zombie memory cgroup when lazytime is enabled, as inodes
with dirty timestamps can not be switched to a live cgwb for a long time.
It is reasonable not to switch cgwb for inodes with dirty data, as
otherwise it may break the bandwidth restrictions. However since the
writeback of inode metadata is not accounted for, let's also switch
inodes with dirty timestamps to avoid zombie memory and block cgroups
when laztytime is enabled.
Fixes: c22d70a162d3 ("writeback, cgroup: release dying cgwbs by switching attached inodes")
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Link: https://lore.kernel.org/r/20231014125511.102978-1-jefflexu@linux.alibaba.com
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
|
|
When writing back an inode and performing an fsync on it concurrently, a
deadlock issue may arise as shown below. In each writeback iteration, a
clean inode is requeued to the wb->b_dirty queue due to non-zero
pages_skipped, without anything actually being written. This causes an
infinite loop and prevents the plug from being flushed, resulting in a
deadlock. We now avoid requeuing the clean inode to prevent this issue.
wb_writeback fsync (inode-Y)
blk_start_plug(&plug)
for (;;) {
iter i-1: some reqs with page-X added into plug->mq_list // f2fs node page-X with PG_writeback
filemap_fdatawrite
__filemap_fdatawrite_range // write inode-Y with sync_mode WB_SYNC_ALL
do_writepages
f2fs_write_data_pages
__f2fs_write_data_pages // wb_sync_req[DATA]++ for WB_SYNC_ALL
f2fs_write_cache_pages
f2fs_write_single_data_page
f2fs_do_write_data_page
f2fs_outplace_write_data
f2fs_update_data_blkaddr
f2fs_wait_on_page_writeback
wait_on_page_writeback // wait for f2fs node page-X
iter i:
progress = __writeback_inodes_wb(wb, work)
. writeback_sb_inodes
. __writeback_single_inode // write inode-Y with sync_mode WB_SYNC_NONE
. . do_writepages
. . f2fs_write_data_pages
. . . __f2fs_write_data_pages // skip writepages due to (wb_sync_req[DATA]>0)
. . . wbc->pages_skipped += get_dirty_pages(inode) // wbc->pages_skipped = 1
. if (!(inode->i_state & I_DIRTY_ALL)) // i_state = I_SYNC | I_SYNC_QUEUED
. total_wrote++; // total_wrote = 1
. requeue_inode // requeue inode-Y to wb->b_dirty queue due to non-zero pages_skipped
if (progress) // progress = 1
continue;
iter i+1:
queue_io
// similar process with iter i, infinite for-loop !
}
blk_finish_plug(&plug) // flush plug won't be called
Signed-off-by: Chunhai Guo <guochunhai@vivo.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Message-Id: <20230916045131.957929-1-guochunhai@vivo.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
|
|
Make the naming consistent with the earlier introduced
super_lock_{read,write}() helpers.
Reviewed-by: Jan Kara <jack@suse.cz>
Message-Id: <20230818-vfs-super-fixes-v3-v3-2-9f0b1876e46b@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
|
|
Patch series "cgroup: eliminate atomic rstat flushing", v5.
A previous patch series [1] changed most atomic rstat flushing contexts to
become non-atomic. This was done to avoid an expensive operation that
scales with # cgroups and # cpus to happen with irqs disabled and
scheduling not permitted. There were two remaining atomic flushing
contexts after that series. This series tries to eliminate them as well,
eliminating atomic rstat flushing completely.
The two remaining atomic flushing contexts are:
(a) wb_over_bg_thresh()->mem_cgroup_wb_stats()
(b) mem_cgroup_threshold()->mem_cgroup_usage()
For (a), flushing needs to be atomic as wb_writeback() calls
wb_over_bg_thresh() with a spinlock held. However, it seems like the call
to wb_over_bg_thresh() doesn't need to be protected by that spinlock, so
this series proposes a refactoring that moves the call outside the lock
criticial section and makes the stats flushing in mem_cgroup_wb_stats()
non-atomic.
For (b), flushing needs to be atomic as mem_cgroup_threshold() is called
with irqs disabled. We only flush the stats when calculating the root
usage, as it is approximated as the sum of some memcg stats (file, anon,
and optionally swap) instead of the conventional page counter. This
series proposes changing this calculation to use the global stats instead,
eliminating the need for a memcg stat flush.
After these 2 contexts are eliminated, we no longer need
mem_cgroup_flush_stats_atomic() or cgroup_rstat_flush_atomic(). We can
remove them and simplify the code.
[1] https://lore.kernel.org/linux-mm/20230330191801.1967435-1-yosryahmed@google.com/
This patch (of 5):
wb_over_bg_thresh() calls mem_cgroup_wb_stats() which invokes an rstat
flush, which can be expensive on large systems. Currently,
wb_writeback() calls wb_over_bg_thresh() within a lock section, so we
have to do the rstat flush atomically. On systems with a lot of
cpus and/or cgroups, this can cause us to disable irqs for a long time,
potentially causing problems.
Move the call to wb_over_bg_thresh() outside the lock section in
preparation to make the rstat flush in mem_cgroup_wb_stats() non-atomic.
The list_empty(&wb->work_list) check should be okay outside the lock
section of wb->list_lock as it is protected by a separate lock
(wb->work_lock), and wb_over_bg_thresh() doesn't seem like it is
modifying any of wb->b_* lists the wb->list_lock is protecting.
Also, the loop seems to be already releasing and reacquring the
lock, so this refactoring looks safe.
Link: https://lkml.kernel.org/r/20230421174020.2994750-1-yosryahmed@google.com
Link: https://lkml.kernel.org/r/20230421174020.2994750-2-yosryahmed@google.com
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Michal Koutný <mkoutny@suse.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Pull more block updates from Jens Axboe:
- MD pull request via Song:
- Improve raid5 sequential IO performance on spinning disks, which
fixes a regression since v6.0 (Jan Kara)
- Fix bitmap offset types, which fixes an issue introduced in this
merge window (Jonathan Derrick)
- Cleanup of hweight type used for cgroup writeback (Maxim)
- Fix a regression with the "has_submit_bio" changes across partitions
(Ming)
- Cleanup of QUEUE_FLAG_ADD_RANDOM clearing.
We used to set this flag on queues non blk-mq queues, and hence some
drivers clear it unconditionally. Since all of these have since been
converted to true blk-mq drivers, drop the useless clear as the bit
is not set (Chaitanya)
- Fix the flags being set in a bio for a flush for drbd (Christoph)
- Cleanup and deduplication of the code handling setting block device
capacity (Damien)
- Fix for ublk handling IO timeouts (Ming)
- Fix for a regression in blk-cgroup teardown (Tao)
- NBD documentation and code fixes (Eric)
- Convert blk-integrity to using device_attributes rather than a second
kobject to manage lifetimes (Thomas)
* tag 'for-6.4/block-2023-05-06' of git://git.kernel.dk/linux:
ublk: add timeout handler
drbd: correctly submit flush bio on barrier
mailmap: add mailmap entries for Jens Axboe
block: Skip destroyed blkg when restart in blkg_destroy_all()
writeback: fix call of incorrect macro
md: Fix bitmap offset type in sb writer
md/raid5: Improve performance for sequential IO
docs nbd: userspace NBD now favors github over sourceforge
block nbd: use req.cookie instead of req.handle
uapi nbd: add cookie alias to handle
uapi nbd: improve doc links to userspace spec
blk-integrity: register sysfs attributes on struct device
blk-integrity: convert to struct device_attribute
blk-integrity: use sysfs_emit
block/drivers: remove dead clear of random flag
block: sync part's ->bd_has_submit_bio with disk's
block: Cleanup set_capacity()/bdev_set_nr_sectors()
|
|
the variable 'history' is of type u16, it may be an error
that the hweight32 macro was used for it
I guess macro hweight16 should be used
Found by Linux Verification Center (linuxtesting.org) with SVACE.
Fixes: 2a81490811d0 ("writeback: implement foreign cgroup inode detection")
Signed-off-by: Maxim Korotkov <korotkov.maxim.s@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20230119104443.3002-1-korotkov.maxim.s@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
|
|
KASAN report null-ptr-deref:
==================================================================
BUG: KASAN: null-ptr-deref in bdi_split_work_to_wbs+0x5c5/0x7b0
Write of size 8 at addr 0000000000000000 by task sync/943
CPU: 5 PID: 943 Comm: sync Tainted: 6.3.0-rc5-next-20230406-dirty #461
Call Trace:
<TASK>
dump_stack_lvl+0x7f/0xc0
print_report+0x2ba/0x340
kasan_report+0xc4/0x120
kasan_check_range+0x1b7/0x2e0
__kasan_check_write+0x24/0x40
bdi_split_work_to_wbs+0x5c5/0x7b0
sync_inodes_sb+0x195/0x630
sync_inodes_one_sb+0x3a/0x50
iterate_supers+0x106/0x1b0
ksys_sync+0x98/0x160
[...]
==================================================================
The race that causes the above issue is as follows:
cpu1 cpu2
-------------------------|-------------------------
inode_switch_wbs
INIT_WORK(&isw->work, inode_switch_wbs_work_fn)
queue_rcu_work(isw_wq, &isw->work)
// queue_work async
inode_switch_wbs_work_fn
wb_put_many(old_wb, nr_switched)
percpu_ref_put_many
ref->data->release(ref)
cgwb_release
queue_work(cgwb_release_wq, &wb->release_work)
// queue_work async
&wb->release_work
cgwb_release_workfn
ksys_sync
iterate_supers
sync_inodes_one_sb
sync_inodes_sb
bdi_split_work_to_wbs
kmalloc(sizeof(*work), GFP_ATOMIC)
// alloc memory failed
percpu_ref_exit
ref->data = NULL
kfree(data)
wb_get(wb)
percpu_ref_get(&wb->refcnt)
percpu_ref_get_many(ref, 1)
atomic_long_add(nr, &ref->data->count)
atomic64_add(i, v)
// trigger null-ptr-deref
bdi_split_work_to_wbs() traverses &bdi->wb_list to split work into all
wbs. If the allocation of new work fails, the on-stack fallback will be
used and the reference count of the current wb is increased afterwards.
If cgroup writeback membership switches occur before getting the reference
count and the current wb is released as old_wd, then calling wb_get() or
wb_put() will trigger the null pointer dereference above.
This issue was introduced in v4.3-rc7 (see fix tag1). Both
sync_inodes_sb() and __writeback_inodes_sb_nr() calls to
bdi_split_work_to_wbs() can trigger this issue. For scenarios called via
sync_inodes_sb(), originally commit 7fc5854f8c6e ("writeback: synchronize
sync(2) against cgroup writeback membership switches") reduced the
possibility of the issue by adding wb_switch_rwsem, but in v5.14-rc1 (see
fix tag2) removed the "inode_io_list_del_locked(inode, old_wb)" from
inode_switch_wbs_work_fn() so that wb->state contains WB_has_dirty_io,
thus old_wb is not skipped when traversing wbs in bdi_split_work_to_wbs(),
and the issue becomes easily reproducible again.
To solve this problem, percpu_ref_exit() is called under RCU protection to
avoid race between cgwb_release_workfn() and bdi_split_work_to_wbs().
Moreover, replace wb_get() with wb_tryget() in bdi_split_work_to_wbs(),
and skip the current wb if wb_tryget() fails because the wb has already
been shutdown.
Link: https://lkml.kernel.org/r/20230410130826.1492525-1-libaokun1@huawei.com
Fixes: b817525a4a80 ("writeback: bdi_writeback iteration must not skip dying ones")
Signed-off-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Hou Tao <houtao1@huawei.com>
Cc: yangerkun <yangerkun@huawei.com>
Cc: Zhang Yi <yi.zhang@huawei.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Only one caller doesn't have a folio, so move the page_folio() call to
that one caller from mem_cgroup_css_from_folio().
Link: https://lkml.kernel.org/r/20230116192507.2146150-3-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Patch series "Writeback folio conversions".
Remove more calls to compound_head() by passing folios around instead of
pages.
This patch (of 2):
The only caller of inode_attach_wb() which doesn't pass NULL already has a
folio, so convert the whole call-chain to take folios.
Link: https://lkml.kernel.org/r/20230116192507.2146150-1-willy@infradead.org
Link: https://lkml.kernel.org/r/20230116192507.2146150-2-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Pull writeback updates from Jens Axboe:
- Sanity check adding freed inodes to lists (Jan)
- Removal of an old unused define (Miaohe)
* tag 'for-6.2/writeback-2022-12-12' of git://git.kernel.dk/linux:
writeback: remove obsolete macro EXPIRE_DIRTY_ATIME
writeback: Add asserts for adding freed inode to lists
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EXPIRE_DIRTY_ATIME is not used anymore. Remove it.
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20221210101042.2012931-1-linmiaohe@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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In the past we had several use-after-free issues with inodes getting
added to writeback lists after evict() removed them. These are painful
to debug so add some asserts to catch the problem earlier. The only
non-obvious change in the commit is that we need to tweak
redirty_tail_locked() to avoid triggering assertion in
inode_io_list_move_locked().
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20221212113633.29181-1-jack@suse.cz
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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After commit cbfecb927f42 ("fs: record I_DIRTY_TIME even if inode
already has I_DIRTY_INODE") writeback_single_inode can push inode with
I_DIRTY_TIME set to b_dirty_time list. In case of freeing inode with
I_DIRTY_TIME set this can happen after deletion of inode from i_io_list
at evict. Stack trace is following.
evict
fat_evict_inode
fat_truncate_blocks
fat_flush_inodes
writeback_inode
sync_inode_metadata(inode, sync=0)
writeback_single_inode(inode, wbc) <- wbc->sync_mode == WB_SYNC_NONE
This will lead to use after free in flusher thread.
Similar issue can be triggered if writeback_single_inode in the
stack trace update inode->i_io_list. Add explicit check to avoid it.
Fixes: cbfecb927f42 ("fs: record I_DIRTY_TIME even if inode already has I_DIRTY_INODE")
Reported-by: syzbot+6ba92bd00d5093f7e371@syzkaller.appspotmail.com
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Svyatoslav Feldsherov <feldsherov@google.com>
Link: https://lore.kernel.org/r/20221115202001.324188-1-feldsherov@google.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
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Currently the I_DIRTY_TIME will never get set if the inode already has
I_DIRTY_INODE with assumption that it supersedes I_DIRTY_TIME. That's
true, however ext4 will only update the on-disk inode in
->dirty_inode(), not on actual writeback. As a result if the inode
already has I_DIRTY_INODE state by the time we get to
__mark_inode_dirty() only with I_DIRTY_TIME, the time was already filled
into on-disk inode and will not get updated until the next I_DIRTY_INODE
update, which might never come if we crash or get a power failure.
The problem can be reproduced on ext4 by running xfstest generic/622
with -o iversion mount option.
Fix it by allowing I_DIRTY_TIME to be set even if the inode already has
I_DIRTY_INODE. Also make sure that the case is properly handled in
writeback_single_inode() as well. Additionally changes in
xfs_fs_dirty_inode() was made to accommodate for I_DIRTY_TIME in flag.
Thanks Jan Kara for suggestions on how to make this work properly.
Cc: Dave Chinner <david@fromorbit.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: stable@kernel.org
Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Suggested-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20220825100657.44217-1-lczerner@redhat.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
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When a disk is removed, bdi_unregister gets called to stop further
writeback and wait for associated delayed work to complete. However,
wb_inode_writeback_end() may schedule bandwidth estimation dwork after
this has completed, which can result in the timer attempting to access the
just freed bdi_writeback.
Fix this by checking if the bdi_writeback is alive, similar to when
scheduling writeback work.
Since this requires wb->work_lock, and wb_inode_writeback_end() may get
called from interrupt, switch wb->work_lock to an irqsafe lock.
Link: https://lkml.kernel.org/r/20220801155034.3772543-1-khazhy@google.com
Fixes: 45a2966fd641 ("writeback: fix bandwidth estimate for spiky workload")
Signed-off-by: Khazhismel Kumykov <khazhy@google.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Michael Stapelberg <stapelberg+linux@google.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Commit b35250c0816c ("writeback: Protect inode->i_io_list with
inode->i_lock") made inode->i_io_list not only protected by
wb->list_lock but also inode->i_lock, but inode_io_list_move_locked()
was missed. Add lock there and also update comment describing
things protected by inode->i_lock. This also fixes a race where
__mark_inode_dirty() could move inode under flush worker's hands
and thus sync(2) could miss writing some inodes.
Fixes: b35250c0816c ("writeback: Protect inode->i_io_list with inode->i_lock")
Link: https://lore.kernel.org/r/20220524150540.12552-1-sunjunchao2870@gmail.com
CC: stable@vger.kernel.org
Signed-off-by: Jchao Sun <sunjunchao2870@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs
Pull writeback and ext2 cleanups from Jan Kara:
"One small ext2 cleanup and one writeback spelling fix"
* tag 'fs_for_v5.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs:
writeback: fix typo in comment
fs: ext2: Fix duplicate included linux/dax.h
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Spelling mistake (triple letters) in comment.
Detected with the help of Coccinelle.
Link: https://lore.kernel.org/r/20220521111145.81697-32-Julia.Lawall@inria.fr
Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>
Signed-off-by: Jan Kara <jack@suse.cz>
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Commit 505a666ee3fc ("writeback: plug writeback in wb_writeback() and
writeback_inodes_wb()") has us holding a plug during wb_writeback, which
may cause a potential ABBA dead lock:
wb_writeback fat_file_fsync
blk_start_plug(&plug)
for (;;) {
iter i-1: some reqs have been added into plug->mq_list // LOCK A
iter i:
progress = __writeback_inodes_wb(wb, work)
. writeback_sb_inodes // fat's bdev
. __writeback_single_inode
. . generic_writepages
. . __block_write_full_page
. . . . __generic_file_fsync
. . . . sync_inode_metadata
. . . . writeback_single_inode
. . . . __writeback_single_inode
. . . . fat_write_inode
. . . . __fat_write_inode
. . . . sync_dirty_buffer // fat's bdev
. . . . lock_buffer(bh) // LOCK B
. . . . submit_bh
. . . . blk_mq_get_tag // LOCK A
. . . trylock_buffer(bh) // LOCK B
. . . redirty_page_for_writepage
. . . wbc->pages_skipped++
. . --wbc->nr_to_write
. wrote += write_chunk - wbc.nr_to_write // wrote > 0
. requeue_inode
. redirty_tail_locked
if (progress) // progress > 0
continue;
iter i+1:
queue_io
// similar process with iter i, infinite for-loop !
}
blk_finish_plug(&plug) // flush plug won't be called
Above process triggers a hungtask like:
[ 399.044861] INFO: task bb:2607 blocked for more than 30 seconds.
[ 399.046824] Not tainted 5.18.0-rc1-00005-gefae4d9eb6a2-dirty
[ 399.051539] task:bb state:D stack: 0 pid: 2607 ppid:
2426 flags:0x00004000
[ 399.051556] Call Trace:
[ 399.051570] __schedule+0x480/0x1050
[ 399.051592] schedule+0x92/0x1a0
[ 399.051602] io_schedule+0x22/0x50
[ 399.051613] blk_mq_get_tag+0x1d3/0x3c0
[ 399.051640] __blk_mq_alloc_requests+0x21d/0x3f0
[ 399.051657] blk_mq_submit_bio+0x68d/0xca0
[ 399.051674] __submit_bio+0x1b5/0x2d0
[ 399.051708] submit_bio_noacct+0x34e/0x720
[ 399.051718] submit_bio+0x3b/0x150
[ 399.051725] submit_bh_wbc+0x161/0x230
[ 399.051734] __sync_dirty_buffer+0xd1/0x420
[ 399.051744] sync_dirty_buffer+0x17/0x20
[ 399.051750] __fat_write_inode+0x289/0x310
[ 399.051766] fat_write_inode+0x2a/0xa0
[ 399.051783] __writeback_single_inode+0x53c/0x6f0
[ 399.051795] writeback_single_inode+0x145/0x200
[ 399.051803] sync_inode_metadata+0x45/0x70
[ 399.051856] __generic_file_fsync+0xa3/0x150
[ 399.051880] fat_file_fsync+0x1d/0x80
[ 399.051895] vfs_fsync_range+0x40/0xb0
[ 399.051929] __x64_sys_fsync+0x18/0x30
In my test, 'need_resched()' (which is imported by 590dca3a71 "fs-writeback:
unplug before cond_resched in writeback_sb_inodes") in function
'writeback_sb_inodes()' seldom comes true, unless cond_resched() is deleted
from write_cache_pages().
Fix it by correcting wrote number according number of skipped pages
in writeback_sb_inodes().
Goto Link to find a reproducer.
Link: https://bugzilla.kernel.org/show_bug.cgi?id=215837
Cc: stable@vger.kernel.org # v4.3
Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220510133805.1988292-1-chengzhihao1@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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