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In earlier patches we moved both nsfs and pidfs to path_from_stashed().
The helper currently tries to add and stash a new dentry if a reusable
dentry couldn't be found and returns EAGAIN if it lost the race to stash
the dentry. The caller can use EAGAIN to retry.
The helper and the two filesystems be written in a way that makes
returning EAGAIN unnecessary. To do this we need to change the
dentry->d_prune() implementation of nsfs and pidfs to not simply replace
the stashed dentry with NULL but to use a cmpxchg() and only replace
their own dentry.
Then path_from_stashed() can then be changed to not just stash a new
dentry when no dentry is currently stashed but also when an already dead
dentry is stashed. If another task managed to install a dentry in the
meantime it can simply be reused. Pack that into a loop and call it a
day.
Suggested-by: Linus Torvalds <[email protected]>
Link: https://lore.kernel.org/r/CAHk-=wgtLF5Z5=15-LKAczWm=-tUjHO+Bpf7WjBG+UU3s=fEQw@mail.gmail.com
Signed-off-by: Christian Brauner <[email protected]>
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Moving pidfds from the anonymous inode infrastructure to a separate tiny
in-kernel filesystem similar to sockfs, pipefs, and anon_inodefs causes
selinux denials and thus various userspace components that make heavy
use of pidfds to fail as pidfds used anon_inode_getfile() which aren't
subject to any LSM hooks. But dentry_open() is and that would cause
regressions.
The failures that are seen are selinux denials. But the core failure is
dbus-broker. That cascades into other services failing that depend on
dbus-broker. For example, when dbus-broker fails to start polkit and all
the others won't be able to work because they depend on dbus-broker.
The reason for dbus-broker failing is because it doesn't handle failures
for SO_PEERPIDFD correctly. Last kernel release we introduced
SO_PEERPIDFD (and SCM_PIDFD). SO_PEERPIDFD allows dbus-broker and polkit
and others to receive a pidfd for the peer of an AF_UNIX socket. This is
the first time in the history of Linux that we can safely authenticate
clients in a race-free manner.
dbus-broker immediately made use of this but messed up the error
checking. It only allowed EINVAL as a valid failure for SO_PEERPIDFD.
That's obviously problematic not just because of LSM denials but because
of seccomp denials that would prevent SO_PEERPIDFD from working; or any
other new error code from there.
So this is catching a flawed implementation in dbus-broker as well. It
has to fallback to the old pid-based authentication when SO_PEERPIDFD
doesn't work no matter the reasons otherwise it'll always risk such
failures. So overall that LSM denial should not have caused dbus-broker
to fail. It can never assume that a feature released one kernel ago like
SO_PEERPIDFD can be assumed to be available.
So, the next fix separate from the selinux policy update is to try and
fix dbus-broker at [3]. That should make it into Fedora as well. In
addition the selinux reference policy should also be updated. See [4]
for that. If Selinux is in enforcing mode in userspace and it encounters
anything that it doesn't know about it will deny it by default. And the
policy is entirely in userspace including declaring new types for stuff
like nsfs or pidfs to allow it.
For now we continue to raise S_PRIVATE on the inode if it's a pidfs
inode which means things behave exactly like before.
Link: https://bugzilla.redhat.com/show_bug.cgi?id=2265630
Link: https://github.com/fedora-selinux/selinux-policy/pull/2050
Link: https://github.com/bus1/dbus-broker/pull/343 [3]
Link: https://github.com/SELinuxProject/refpolicy/pull/762 [4]
Reported-by: Nathan Chancellor <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Link: https://lore.kernel.org/r/20240218-neufahrzeuge-brauhaus-fb0eb6459771@brauner
Signed-off-by: Christian Brauner <[email protected]>
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Use the newly added path_from_stashed() helper for nsfs.
Link: https://lore.kernel.org/r/20240218-neufahrzeuge-brauhaus-fb0eb6459771@brauner
Signed-off-by: Christian Brauner <[email protected]>
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Add a helper for both nsfs and pidfs to reuse an already stashed dentry
or to add and stash a new dentry.
Link: https://lore.kernel.org/r/20240218-neufahrzeuge-brauhaus-fb0eb6459771@brauner
Signed-off-by: Christian Brauner <[email protected]>
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This moves pidfds from the anonymous inode infrastructure to a tiny
pseudo filesystem. This has been on my todo for quite a while as it will
unblock further work that we weren't able to do simply because of the
very justified limitations of anonymous inodes. Moving pidfds to a tiny
pseudo filesystem allows:
* statx() on pidfds becomes useful for the first time.
* pidfds can be compared simply via statx() and then comparing inode
numbers.
* pidfds have unique inode numbers for the system lifetime.
* struct pid is now stashed in inode->i_private instead of
file->private_data. This means it is now possible to introduce
concepts that operate on a process once all file descriptors have been
closed. A concrete example is kill-on-last-close.
* file->private_data is freed up for per-file options for pidfds.
* Each struct pid will refer to a different inode but the same struct
pid will refer to the same inode if it's opened multiple times. In
contrast to now where each struct pid refers to the same inode. Even
if we were to move to anon_inode_create_getfile() which creates new
inodes we'd still be associating the same struct pid with multiple
different inodes.
The tiny pseudo filesystem is not visible anywhere in userspace exactly
like e.g., pipefs and sockfs. There's no lookup, there's no complex
inode operations, nothing. Dentries and inodes are always deleted when
the last pidfd is closed.
We allocate a new inode for each struct pid and we reuse that inode for
all pidfds. We use iget_locked() to find that inode again based on the
inode number which isn't recycled. We allocate a new dentry for each
pidfd that uses the same inode. That is similar to anonymous inodes
which reuse the same inode for thousands of dentries. For pidfds we're
talking way less than that. There usually won't be a lot of concurrent
openers of the same struct pid. They can probably often be counted on
two hands. I know that systemd does use separate pidfd for the same
struct pid for various complex process tracking issues. So I think with
that things actually become way simpler. Especially because we don't
have to care about lookup. Dentries and inodes continue to be always
deleted.
The code is entirely optional and fairly small. If it's not selected we
fallback to anonymous inodes. Heavily inspired by nsfs which uses a
similar stashing mechanism just for namespaces.
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Christian Brauner <[email protected]>
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Move the pidfd file operations over to their own file in preparation of
implementing pidfs and to isolate them from other mostly unrelated
functionality in other files.
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Christian Brauner <[email protected]>
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Right now we determine the scope of the signal based on the type of
pidfd. There are use-cases where it's useful to override the scope of
the signal. For example in [1]. Add flags to determine the scope of the
signal:
(1) PIDFD_SIGNAL_THREAD: send signal to specific thread reference by @pidfd
(2) PIDFD_SIGNAL_THREAD_GROUP: send signal to thread-group of @pidfd
(2) PIDFD_SIGNAL_PROCESS_GROUP: send signal to process-group of @pidfd
Since we now allow specifying PIDFD_SEND_PROCESS_GROUP for
pidfd_send_signal() to send signals to process groups we need to adjust
the check restricting si_code emulation by userspace to account for
PIDTYPE_PGID.
Reviewed-by: Oleg Nesterov <[email protected]>
Link: https://github.com/systemd/systemd/issues/31093 [1]
Link: https://lore.kernel.org/r/20240210-chihuahua-hinzog-3945b6abd44a@brauner
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Christian Brauner <[email protected]>
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Turn kill_pid_info() into kill_pid_info_type(), this allows to pass any
pid_type to group_send_sig_info(), despite its name it should work fine
even if type = PIDTYPE_PID.
Change pidfd_send_signal() to use PIDTYPE_PID or PIDTYPE_TGID depending
on PIDFD_THREAD.
While at it kill another TODO comment in pidfd_show_fdinfo(). As Christian
expains fdinfo reports f_flags, userspace can already detect PIDFD_THREAD.
Reviewed-by: Tycho Andersen <[email protected]>
Signed-off-by: Oleg Nesterov <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Christian Brauner <[email protected]>
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So that do_tkill() can use this helper too. This also simplifies
the next patch.
TODO: perhaps we can kill prepare_kill_siginfo() and change the
callers to use SEND_SIG_NOINFO, but this needs some changes in
__send_signal_locked() and TP_STORE_SIGINFO().
Reviewed-by: Tycho Andersen <[email protected]>
Signed-off-by: Oleg Nesterov <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Christian Brauner <[email protected]>
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Ensure that pidfd_getfd() reports -ESRCH if the task is already exiting.
Signed-off-by: Tycho Andersen <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Christian Brauner <[email protected]>
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We can get EBADF from pidfd_getfd() if a task is currently exiting,
which might be confusing. Let's check PF_EXITING, and just report ESRCH
if so.
I chose PF_EXITING, because it is set in exit_signals(), which is called
before exit_files(). Since ->exit_status is mostly set after
exit_files() in exit_notify(), using that still leaves a window open for
the race.
Reviewed-by: Oleg Nesterov <[email protected]>
Signed-off-by: Tycho Andersen <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Christian Brauner <[email protected]>
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copy_process() just needs to pass PIDFD_THREAD to __pidfd_prepare()
if clone_flags & CLONE_THREAD.
We can also add another CLONE_ flag (or perhaps reuse CLONE_DETACHED)
to enforce PIDFD_THREAD without CLONE_THREAD.
Originally-from: Tycho Andersen <[email protected]>
Signed-off-by: Oleg Nesterov <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Reviewed-by: Tycho Andersen <[email protected]>
Signed-off-by: Christian Brauner <[email protected]>
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It was used by pidfd_poll() but now it has no callers.
If it finally finds a modular user we can revert this change, but note
that the comment above this helper and the changelog in 38fd525a4c61
("exit: Factor thread_group_exited out of pidfd_poll") are not accurate,
thread_group_exited() won't return true if all other threads have passed
exit_notify() and are zombies, it returns true only when all other threads
are completely gone. Not to mention that it can only work if the task
identified by @pid is a thread-group leader.
Signed-off-by: Oleg Nesterov <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Reviewed-by: Tycho Andersen <[email protected]>
Signed-off-by: Christian Brauner <[email protected]>
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rather than wake_up_all(). This way do_notify_pidfd() won't wakeup the
POLLHUP-only waiters which wait for pid_task() == NULL.
TODO:
- as Christian pointed out, this asks for the new wake_up_all_poll()
helper, it can already have other users.
- we can probably discriminate the PIDFD_THREAD and non-PIDFD_THREAD
waiters, but this needs more work. See
https://lore.kernel.org/all/[email protected]/
Signed-off-by: Oleg Nesterov <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Reviewed-by: Tycho Andersen <[email protected]>
Signed-off-by: Christian Brauner <[email protected]>
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transfer_pid() must be never called with pid == PIDTYPE_PID,
new_leader->thread_pid should be changed by exchange_tids().
Signed-off-by: Oleg Nesterov <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Christian Brauner <[email protected]>
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Now that __change_pid() does wake_up_all(&pid->wait_pidfd) we can kill
do_notify_pidfd(leader) in de_thread(), it calls release_task(leader)
right after that and this implies detach_pid(leader, PIDTYPE_PID).
Signed-off-by: Oleg Nesterov <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Christian Brauner <[email protected]>
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Add another wake_up_all(wait_pidfd) into __change_pid() and change
pidfd_poll() to include EPOLLHUP if task == NULL.
This allows to wait until the target process/thread is reaped.
TODO: change do_notify_pidfd() to use the keyed wakeups.
Signed-off-by: Oleg Nesterov <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Christian Brauner <[email protected]>
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With this flag:
- pidfd_open() doesn't require that the target task must be
a thread-group leader
- pidfd_poll() succeeds when the task exits and becomes a
zombie (iow, passes exit_notify()), even if it is a leader
and thread-group is not empty.
This means that the behaviour of pidfd_poll(PIDFD_THREAD,
pid-of-group-leader) is not well defined if it races with
exec() from its sub-thread; pidfd_poll() can succeed or not
depending on whether pidfd_task_exited() is called before
or after exchange_tids().
Perhaps we can improve this behaviour later, pidfd_poll()
can probably take sig->group_exec_task into account. But
this doesn't really differ from the case when the leader
exits before other threads (so pidfd_poll() succeeds) and
then another thread execs and pidfd_poll() will block again.
thread_group_exited() is no longer used, perhaps it can die.
Co-developed-by: Tycho Andersen <[email protected]>
Signed-off-by: Oleg Nesterov <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Tested-by: Tycho Andersen <[email protected]>
Reviewed-by: Tycho Andersen <[email protected]>
Signed-off-by: Christian Brauner <[email protected]>
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do_notify_pidfd() makes no sense until the whole thread group exits, change
do_notify_parent() to check thread_group_empty().
This avoids the unnecessary do_notify_pidfd() when tsk is not a leader, or
it exits before other threads, or it has a ptraced EXIT_ZOMBIE sub-thread.
Signed-off-by: Oleg Nesterov <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Reviewed-by: Tycho Andersen <[email protected]>
Signed-off-by: Christian Brauner <[email protected]>
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- make pidfd_create() static.
- Don't pass O_RDWR | O_CLOEXEC to __pidfd_prepare() in copy_process(),
__pidfd_prepare() adds these flags unconditionally.
- Kill the flags check in __pidfd_prepare(). sys_pidfd_open() checks the
flags itself, all other users of pidfd_prepare() pass flags = 0.
If we need a sanity check for those other in kernel users then
WARN_ON_ONCE(flags & ~PIDFD_NONBLOCK) makes more sense.
- Don't pass O_RDWR to get_unused_fd_flags(), it ignores everything except
O_CLOEXEC.
- Don't pass O_CLOEXEC to anon_inode_getfile(), it ignores everything except
O_ACCMODE | O_NONBLOCK.
Signed-off-by: Oleg Nesterov <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Christian Brauner <[email protected]>
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In the current implementation of clone(), there is a line that
initializes `u64 clone_flags = args->flags` at the top.
This means that there is no longer a need to use args->flags
for the legacy clone check.
Signed-off-by: Wang Jinchao <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Christian Brauner <[email protected]>
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Pull more bcachefs updates from Kent Overstreet:
"Some fixes, Some refactoring, some minor features:
- Assorted prep work for disk space accounting rewrite
- BTREE_TRIGGER_ATOMIC: after combining our trigger callbacks, this
makes our trigger context more explicit
- A few fixes to avoid excessive transaction restarts on
multithreaded workloads: fstests (in addition to ktest tests) are
now checking slowpath counters, and that's shaking out a few bugs
- Assorted tracepoint improvements
- Starting to break up bcachefs_format.h and move on disk types so
they're with the code they belong to; this will make room to start
documenting the on disk format better.
- A few minor fixes"
* tag 'bcachefs-2024-01-21' of https://evilpiepirate.org/git/bcachefs: (46 commits)
bcachefs: Improve inode_to_text()
bcachefs: logged_ops_format.h
bcachefs: reflink_format.h
bcachefs; extents_format.h
bcachefs: ec_format.h
bcachefs: subvolume_format.h
bcachefs: snapshot_format.h
bcachefs: alloc_background_format.h
bcachefs: xattr_format.h
bcachefs: dirent_format.h
bcachefs: inode_format.h
bcachefs; quota_format.h
bcachefs: sb-counters_format.h
bcachefs: counters.c -> sb-counters.c
bcachefs: comment bch_subvolume
bcachefs: bch_snapshot::btime
bcachefs: add missing __GFP_NOWARN
bcachefs: opts->compression can now also be applied in the background
bcachefs: Prep work for variable size btree node buffers
bcachefs: grab s_umount only if snapshotting
...
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer updates from Thomas Gleixner:
"Updates for time and clocksources:
- A fix for the idle and iowait time accounting vs CPU hotplug.
The time is reset on CPU hotplug which makes the accumulated
systemwide time jump backwards.
- Assorted fixes and improvements for clocksource/event drivers"
* tag 'timers-core-2024-01-21' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
tick-sched: Fix idle and iowait sleeptime accounting vs CPU hotplug
clocksource/drivers/ep93xx: Fix error handling during probe
clocksource/drivers/cadence-ttc: Fix some kernel-doc warnings
clocksource/drivers/timer-ti-dm: Fix make W=n kerneldoc warnings
clocksource/timer-riscv: Add riscv_clock_shutdown callback
dt-bindings: timer: Add StarFive JH8100 clint
dt-bindings: timer: thead,c900-aclint-mtimer: separate mtime and mtimecmp regs
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git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux
Pull powerpc fixes from Aneesh Kumar:
- Increase default stack size to 32KB for Book3S
Thanks to Michael Ellerman.
* tag 'powerpc-6.8-2' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
powerpc/64s: Increase default stack size to 32KB
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Add line breaks - inode_to_text() is now much easier to read.
Signed-off-by: Kent Overstreet <[email protected]>
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Signed-off-by: Kent Overstreet <[email protected]>
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Signed-off-by: Kent Overstreet <[email protected]>
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Signed-off-by: Kent Overstreet <[email protected]>
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Signed-off-by: Kent Overstreet <[email protected]>
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Signed-off-by: Kent Overstreet <[email protected]>
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Signed-off-by: Kent Overstreet <[email protected]>
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Signed-off-by: Kent Overstreet <[email protected]>
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Signed-off-by: Kent Overstreet <[email protected]>
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Signed-off-by: Kent Overstreet <[email protected]>
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Signed-off-by: Kent Overstreet <[email protected]>
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Signed-off-by: Kent Overstreet <[email protected]>
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bcachefs_format.h has gotten too big; let's do some organizing.
Signed-off-by: Kent Overstreet <[email protected]>
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Signed-off-by: Kent Overstreet <[email protected]>
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Signed-off-by: Kent Overstreet <[email protected]>
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Add a field to bch_snapshot for creation time; this will be important
when we start exposing the snapshot tree to userspace.
Signed-off-by: Kent Overstreet <[email protected]>
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Signed-off-by: Kent Overstreet <[email protected]>
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The "apply this compression method in the background" paths now use the
compression option if background_compression is not set; this means that
setting or changing the compression option will cause existing data to
be compressed accordingly in the background.
Signed-off-by: Kent Overstreet <[email protected]>
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bcachefs btree nodes are big - typically 256k - and btree roots are
pinned in memory. As we're now up to 18 btrees, we now have significant
memory overhead in mostly empty btree roots.
And in the future we're going to start enforcing that certain btree node
boundaries exist, to solve lock contention issues - analagous to XFS's
AGIs.
Thus, we need to start allocating smaller btree node buffers when we
can. This patch changes code that refers to the filesystem constant
c->opts.btree_node_size to refer to the btree node buffer size -
btree_buf_bytes() - where appropriate.
Signed-off-by: Kent Overstreet <[email protected]>
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When I was testing mongodb over bcachefs with compression,
there is a lockdep warning when snapshotting mongodb data volume.
$ cat test.sh
prog=bcachefs
$prog subvolume create /mnt/data
$prog subvolume create /mnt/data/snapshots
while true;do
$prog subvolume snapshot /mnt/data /mnt/data/snapshots/$(date +%s)
sleep 1s
done
$ cat /etc/mongodb.conf
systemLog:
destination: file
logAppend: true
path: /mnt/data/mongod.log
storage:
dbPath: /mnt/data/
lockdep reports:
[ 3437.452330] ======================================================
[ 3437.452750] WARNING: possible circular locking dependency detected
[ 3437.453168] 6.7.0-rc7-custom+ #85 Tainted: G E
[ 3437.453562] ------------------------------------------------------
[ 3437.453981] bcachefs/35533 is trying to acquire lock:
[ 3437.454325] ffffa0a02b2b1418 (sb_writers#10){.+.+}-{0:0}, at: filename_create+0x62/0x190
[ 3437.454875]
but task is already holding lock:
[ 3437.455268] ffffa0a02b2b10e0 (&type->s_umount_key#48){.+.+}-{3:3}, at: bch2_fs_file_ioctl+0x232/0xc90 [bcachefs]
[ 3437.456009]
which lock already depends on the new lock.
[ 3437.456553]
the existing dependency chain (in reverse order) is:
[ 3437.457054]
-> #3 (&type->s_umount_key#48){.+.+}-{3:3}:
[ 3437.457507] down_read+0x3e/0x170
[ 3437.457772] bch2_fs_file_ioctl+0x232/0xc90 [bcachefs]
[ 3437.458206] __x64_sys_ioctl+0x93/0xd0
[ 3437.458498] do_syscall_64+0x42/0xf0
[ 3437.458779] entry_SYSCALL_64_after_hwframe+0x6e/0x76
[ 3437.459155]
-> #2 (&c->snapshot_create_lock){++++}-{3:3}:
[ 3437.459615] down_read+0x3e/0x170
[ 3437.459878] bch2_truncate+0x82/0x110 [bcachefs]
[ 3437.460276] bchfs_truncate+0x254/0x3c0 [bcachefs]
[ 3437.460686] notify_change+0x1f1/0x4a0
[ 3437.461283] do_truncate+0x7f/0xd0
[ 3437.461555] path_openat+0xa57/0xce0
[ 3437.461836] do_filp_open+0xb4/0x160
[ 3437.462116] do_sys_openat2+0x91/0xc0
[ 3437.462402] __x64_sys_openat+0x53/0xa0
[ 3437.462701] do_syscall_64+0x42/0xf0
[ 3437.462982] entry_SYSCALL_64_after_hwframe+0x6e/0x76
[ 3437.463359]
-> #1 (&sb->s_type->i_mutex_key#15){+.+.}-{3:3}:
[ 3437.463843] down_write+0x3b/0xc0
[ 3437.464223] bch2_write_iter+0x5b/0xcc0 [bcachefs]
[ 3437.464493] vfs_write+0x21b/0x4c0
[ 3437.464653] ksys_write+0x69/0xf0
[ 3437.464839] do_syscall_64+0x42/0xf0
[ 3437.465009] entry_SYSCALL_64_after_hwframe+0x6e/0x76
[ 3437.465231]
-> #0 (sb_writers#10){.+.+}-{0:0}:
[ 3437.465471] __lock_acquire+0x1455/0x21b0
[ 3437.465656] lock_acquire+0xc6/0x2b0
[ 3437.465822] mnt_want_write+0x46/0x1a0
[ 3437.465996] filename_create+0x62/0x190
[ 3437.466175] user_path_create+0x2d/0x50
[ 3437.466352] bch2_fs_file_ioctl+0x2ec/0xc90 [bcachefs]
[ 3437.466617] __x64_sys_ioctl+0x93/0xd0
[ 3437.466791] do_syscall_64+0x42/0xf0
[ 3437.466957] entry_SYSCALL_64_after_hwframe+0x6e/0x76
[ 3437.467180]
other info that might help us debug this:
[ 3437.469670] 2 locks held by bcachefs/35533:
other info that might help us debug this:
[ 3437.467507] Chain exists of:
sb_writers#10 --> &c->snapshot_create_lock --> &type->s_umount_key#48
[ 3437.467979] Possible unsafe locking scenario:
[ 3437.468223] CPU0 CPU1
[ 3437.468405] ---- ----
[ 3437.468585] rlock(&type->s_umount_key#48);
[ 3437.468758] lock(&c->snapshot_create_lock);
[ 3437.469030] lock(&type->s_umount_key#48);
[ 3437.469291] rlock(sb_writers#10);
[ 3437.469434]
*** DEADLOCK ***
[ 3437.469670] 2 locks held by bcachefs/35533:
[ 3437.469838] #0: ffffa0a02ce00a88 (&c->snapshot_create_lock){++++}-{3:3}, at: bch2_fs_file_ioctl+0x1e3/0xc90 [bcachefs]
[ 3437.470294] #1: ffffa0a02b2b10e0 (&type->s_umount_key#48){.+.+}-{3:3}, at: bch2_fs_file_ioctl+0x232/0xc90 [bcachefs]
[ 3437.470744]
stack backtrace:
[ 3437.470922] CPU: 7 PID: 35533 Comm: bcachefs Kdump: loaded Tainted: G E 6.7.0-rc7-custom+ #85
[ 3437.471313] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Arch Linux 1.16.3-1-1 04/01/2014
[ 3437.471694] Call Trace:
[ 3437.471795] <TASK>
[ 3437.471884] dump_stack_lvl+0x57/0x90
[ 3437.472035] check_noncircular+0x132/0x150
[ 3437.472202] __lock_acquire+0x1455/0x21b0
[ 3437.472369] lock_acquire+0xc6/0x2b0
[ 3437.472518] ? filename_create+0x62/0x190
[ 3437.472683] ? lock_is_held_type+0x97/0x110
[ 3437.472856] mnt_want_write+0x46/0x1a0
[ 3437.473025] ? filename_create+0x62/0x190
[ 3437.473204] filename_create+0x62/0x190
[ 3437.473380] user_path_create+0x2d/0x50
[ 3437.473555] bch2_fs_file_ioctl+0x2ec/0xc90 [bcachefs]
[ 3437.473819] ? lock_acquire+0xc6/0x2b0
[ 3437.474002] ? __fget_files+0x2a/0x190
[ 3437.474195] ? __fget_files+0xbc/0x190
[ 3437.474380] ? lock_release+0xc5/0x270
[ 3437.474567] ? __x64_sys_ioctl+0x93/0xd0
[ 3437.474764] ? __pfx_bch2_fs_file_ioctl+0x10/0x10 [bcachefs]
[ 3437.475090] __x64_sys_ioctl+0x93/0xd0
[ 3437.475277] do_syscall_64+0x42/0xf0
[ 3437.475454] entry_SYSCALL_64_after_hwframe+0x6e/0x76
[ 3437.475691] RIP: 0033:0x7f2743c313af
======================================================
In __bch2_ioctl_subvolume_create(), we grab s_umount unconditionally
and unlock it at the end of the function. There is a comment
"why do we need this lock?" about the lock coming from
commit 42d237320e98 ("bcachefs: Snapshot creation, deletion")
The reason is that __bch2_ioctl_subvolume_create() calls
sync_inodes_sb() which enforce locked s_umount to writeback all dirty
nodes before doing snapshot works.
Fix it by read locking s_umount for snapshotting only and unlocking
s_umount after sync_inodes_sb().
Signed-off-by: Su Yue <[email protected]>
Signed-off-by: Kent Overstreet <[email protected]>
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bch_fs::snapshots is allocated by kvzalloc in __snapshot_t_mut.
It should be freed by kvfree not kfree.
Or umount will triger:
[ 406.829178 ] BUG: unable to handle page fault for address: ffffe7b487148008
[ 406.830676 ] #PF: supervisor read access in kernel mode
[ 406.831643 ] #PF: error_code(0x0000) - not-present page
[ 406.832487 ] PGD 0 P4D 0
[ 406.832898 ] Oops: 0000 [#1] PREEMPT SMP PTI
[ 406.833512 ] CPU: 2 PID: 1754 Comm: umount Kdump: loaded Tainted: G OE 6.7.0-rc7-custom+ #90
[ 406.834746 ] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Arch Linux 1.16.3-1-1 04/01/2014
[ 406.835796 ] RIP: 0010:kfree+0x62/0x140
[ 406.836197 ] Code: 80 48 01 d8 0f 82 e9 00 00 00 48 c7 c2 00 00 00 80 48 2b 15 78 9f 1f 01 48 01 d0 48 c1 e8 0c 48 c1 e0 06 48 03 05 56 9f 1f 01 <48> 8b 50 08 48 89 c7 f6 c2 01 0f 85 b0 00 00 00 66 90 48 8b 07 f6
[ 406.837810 ] RSP: 0018:ffffb9d641607e48 EFLAGS: 00010286
[ 406.838213 ] RAX: ffffe7b487148000 RBX: ffffb9d645200000 RCX: ffffb9d641607dc4
[ 406.838738 ] RDX: 000065bb00000000 RSI: ffffffffc0d88b84 RDI: ffffb9d645200000
[ 406.839217 ] RBP: ffff9a4625d00068 R08: 0000000000000001 R09: 0000000000000001
[ 406.839650 ] R10: 0000000000000001 R11: 000000000000001f R12: ffff9a4625d4da80
[ 406.840055 ] R13: ffff9a4625d00000 R14: ffffffffc0e2eb20 R15: 0000000000000000
[ 406.840451 ] FS: 00007f0a264ffb80(0000) GS:ffff9a4e2d500000(0000) knlGS:0000000000000000
[ 406.840851 ] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 406.841125 ] CR2: ffffe7b487148008 CR3: 000000018c4d2000 CR4: 00000000000006f0
[ 406.841464 ] Call Trace:
[ 406.841583 ] <TASK>
[ 406.841682 ] ? __die+0x1f/0x70
[ 406.841828 ] ? page_fault_oops+0x159/0x470
[ 406.842014 ] ? fixup_exception+0x22/0x310
[ 406.842198 ] ? exc_page_fault+0x1ed/0x200
[ 406.842382 ] ? asm_exc_page_fault+0x22/0x30
[ 406.842574 ] ? bch2_fs_release+0x54/0x280 [bcachefs]
[ 406.842842 ] ? kfree+0x62/0x140
[ 406.842988 ] ? kfree+0x104/0x140
[ 406.843138 ] bch2_fs_release+0x54/0x280 [bcachefs]
[ 406.843390 ] kobject_put+0xb7/0x170
[ 406.843552 ] deactivate_locked_super+0x2f/0xa0
[ 406.843756 ] cleanup_mnt+0xba/0x150
[ 406.843917 ] task_work_run+0x59/0xa0
[ 406.844083 ] exit_to_user_mode_prepare+0x197/0x1a0
[ 406.844302 ] syscall_exit_to_user_mode+0x16/0x40
[ 406.844510 ] do_syscall_64+0x4e/0xf0
[ 406.844675 ] entry_SYSCALL_64_after_hwframe+0x6e/0x76
[ 406.844907 ] RIP: 0033:0x7f0a2664e4fb
Signed-off-by: Su Yue <[email protected]>
Reviewed-by: Brian Foster <[email protected]>
Signed-off-by: Kent Overstreet <[email protected]>
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Fixes: 023f9ac9f70f bcachefs: Delete dio read alignment check
Reported-by: Brian Foster <[email protected]>
Signed-off-by: Kent Overstreet <[email protected]>
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The variable tmp is being assigned a value but it isn't being
read afterwards. The assignment is redundant and so tmp can be
removed.
Cleans up clang scan build warning:
warning: Although the value stored to 'ret' is used in the enclosing
expression, the value is never actually read from 'ret'
[deadcode.DeadStores]
Signed-off-by: Colin Ian King <[email protected]>
Reviewed-by: Brian Foster <[email protected]>
Signed-off-by: Kent Overstreet <[email protected]>
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Signed-off-by: Kent Overstreet <[email protected]>
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drop_locks_do() should not be used in a fastpath without first trying
the do in nonblocking mode - the unlock and relock will cause excessive
transaction restarts and potentially livelocking with other threads that
are contending for the same locks.
Signed-off-by: Kent Overstreet <[email protected]>
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