dquot_scan_active() can race with quota deactivation in
quota_release_workfn() like:
CPU0 (quota_release_workfn) CPU1 (dquot_scan_active)
============================== ==============================
spin_lock(&dq_list_lock);
list_replace_init(
&releasing_dquots, &rls_head);
/* dquot X on rls_head,
dq_count == 0,
DQ_ACTIVE_B still set */
spin_unlock(&dq_list_lock);
synchronize_srcu(&dquot_srcu);
spin_lock(&dq_list_lock);
list_for_each_entry(dquot,
&inuse_list, dq_inuse) {
/* finds dquot X */
dquot_active(X) -> true
atomic_inc(&X->dq_count);
}
spin_unlock(&dq_list_lock);
spin_lock(&dq_list_lock);
dquot = list_first_entry(&rls_head);
WARN_ON_ONCE(atomic_read(&dquot->dq_count));
The problem is not only a cosmetic one as under memory pressure the
caller of dquot_scan_active() can end up working on freed dquot.
Fix the problem by making sure the dquot is removed from releasing list
when we acquire a reference to it.
Fixes: 869b6ea160 ("quota: Fix slow quotaoff")
Reported-by: Sam Sun <samsun1006219@gmail.com>
Link: https://lore.kernel.org/all/CAEkJfYPTt3uP1vAYnQ5V2ZWn5O9PLhhGi5HbOcAzyP9vbXyjeg@mail.gmail.com
Signed-off-by: Jan Kara <jack@suse.cz>
This was done entirely with mindless brute force, using
git grep -l '\<k[vmz]*alloc_objs*(.*, GFP_KERNEL)' |
xargs sed -i 's/\(alloc_objs*(.*\), GFP_KERNEL)/\1)/'
to convert the new alloc_obj() users that had a simple GFP_KERNEL
argument to just drop that argument.
Note that due to the extreme simplicity of the scripting, any slightly
more complex cases spread over multiple lines would not be triggered:
they definitely exist, but this covers the vast bulk of the cases, and
the resulting diff is also then easier to check automatically.
For the same reason the 'flex' versions will be done as a separate
conversion.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This is the result of running the Coccinelle script from
scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to
avoid scalar types (which need careful case-by-case checking), and
instead replace kmalloc-family calls that allocate struct or union
object instances:
Single allocations: kmalloc(sizeof(TYPE), ...)
are replaced with: kmalloc_obj(TYPE, ...)
Array allocations: kmalloc_array(COUNT, sizeof(TYPE), ...)
are replaced with: kmalloc_objs(TYPE, COUNT, ...)
Flex array allocations: kmalloc(struct_size(PTR, FAM, COUNT), ...)
are replaced with: kmalloc_flex(*PTR, FAM, COUNT, ...)
(where TYPE may also be *VAR)
The resulting allocations no longer return "void *", instead returning
"TYPE *".
Signed-off-by: Kees Cook <kees@kernel.org>
Pull quota and isofs updates from Jan Kara:
- a fix for quotactl livelock during filesystem freezing
- a small improvement for isofs
- a documentation fix for ext2
* tag 'fs_for_v6.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs:
isofs: support full length file names (255 instead of 253)
quota: fix livelock between quotactl and freeze_super
doc : fix a broken link in ext2.rst
When a filesystem is frozen, quotactl_block() enters a retry loop
waiting for the filesystem to thaw. It acquires s_umount, checks the
freeze state, drops s_umount and uses sb_start_write() - sb_end_write()
pair to wait for the unfreeze.
However, this retry loop can trigger a livelock issue, specifically on
kernels with preemption disabled.
The mechanism is as follows:
1. freeze_super() sets SB_FREEZE_WRITE and calls sb_wait_write().
2. sb_wait_write() calls percpu_down_write(), which initiates
synchronize_rcu().
3. Simultaneously, quotactl_block() spins in its retry loop, immediately
executing the sb_start_write() - sb_end_write() pair.
4. Because the kernel is non-preemptible and the loop contains no
scheduling points, quotactl_block() never yields the CPU. This
prevents that CPU from reaching an RCU quiescent state.
5. synchronize_rcu() in the freezer thread waits indefinitely for the
quotactl_block() CPU to report a quiescent state.
6. quotactl_block() spins indefinitely waiting for the freezer to
advance, which it cannot do as it is blocked on the RCU sync.
This results in a hang of the freezer process and 100% CPU usage by the
quota process.
While this can occur intermittently on multi-core systems, it is
reliably reproducing on a node with the following script, running both
the freezer and the quota toggle on the same CPU:
# mkfs.ext4 -O quota /dev/sda 2g && mkdir a_mount
# mount /dev/sda -o quota,usrquota,grpquota a_mount
# taskset -c 3 bash -c "while true; do xfs_freeze -f a_mount; \
xfs_freeze -u a_mount; done" &
# taskset -c 3 bash -c "while true; do quotaon a_mount; \
quotaoff a_mount; done" &
Adding cond_resched() to the retry loop fixes the issue. It acts as an
RCU quiescent state, allowing synchronize_rcu() in percpu_down_write()
to complete.
Fixes: 576215cffd ("fs: Drop wait_unfrozen wait queue")
Signed-off-by: Abhishek Bapat <abhishekbapat@google.com>
Link: https://patch.msgid.link/20260115213103.1089129-1-abhishekbapat@google.com
Signed-off-by: Jan Kara <jack@suse.cz>
There is a kernel panic due to WARN_ONCE when panic_on_warn is set.
This issue occurs when writeback is triggered due to sync call for an
opened file(ie, writeback reason is WB_REASON_SYNC). When f2fs balance
is needed at sync path, flush for quota_release_work is triggered.
By default quota_release_work is queued to "events_unbound" queue which
does not have WQ_MEM_RECLAIM flag. During f2fs balance "writeback"
workqueue tries to flush quota_release_work causing kernel panic due to
MEM_RECLAIM flag mismatch errors.
This patch creates dedicated workqueue with WQ_MEM_RECLAIM flag
for work quota_release_work.
------------[ cut here ]------------
WARNING: CPU: 4 PID: 14867 at kernel/workqueue.c:3721 check_flush_dependency+0x13c/0x148
Call trace:
check_flush_dependency+0x13c/0x148
__flush_work+0xd0/0x398
flush_delayed_work+0x44/0x5c
dquot_writeback_dquots+0x54/0x318
f2fs_do_quota_sync+0xb8/0x1a8
f2fs_write_checkpoint+0x3cc/0x99c
f2fs_gc+0x190/0x750
f2fs_balance_fs+0x110/0x168
f2fs_write_single_data_page+0x474/0x7dc
f2fs_write_data_pages+0x7d0/0xd0c
do_writepages+0xe0/0x2f4
__writeback_single_inode+0x44/0x4ac
writeback_sb_inodes+0x30c/0x538
wb_writeback+0xf4/0x440
wb_workfn+0x128/0x5d4
process_scheduled_works+0x1c4/0x45c
worker_thread+0x32c/0x3e8
kthread+0x11c/0x1b0
ret_from_fork+0x10/0x20
Kernel panic - not syncing: kernel: panic_on_warn set ...
Fixes: ac6f420291 ("quota: flush quota_release_work upon quota writeback")
CC: stable@vger.kernel.org
Signed-off-by: Shashank A P <shashank.ap@samsung.com>
Link: https://patch.msgid.link/20250901092905.2115-1-shashank.ap@samsung.com
Signed-off-by: Jan Kara <jack@suse.cz>
The lookup_one_len family of functions is (now) only used internally by
a filesystem on itself either
- in a context where permission checking is irrelevant such as by a
virtual filesystem populating itself, or xfs accessing its ORPHANAGE
or dquota accessing the quota file; or
- in a context where a permission check (MAY_EXEC on the parent) has just
been performed such as a network filesystem finding in "silly-rename"
file in the same directory. This is also the context after the
_parentat() functions where currently lookup_one_qstr_excl() is used.
So the permission check is pointless.
The name "one_len" is unhelpful in understanding the purpose of these
functions and should be changed. Most of the callers pass the len as
"strlen()" so using a qstr and QSTR() can simplify the code.
This patch renames these functions (include lookup_positive_unlocked()
which is part of the family despite the name) to have a name based on
"lookup_noperm". They are changed to receive a 'struct qstr' instead
of separate name and len. In a few cases the use of QSTR() results in a
new call to strlen().
try_lookup_noperm() takes a pointer to a qstr instead of the whole
qstr. This is consistent with d_hash_and_lookup() (which is nearly
identical) and useful for lookup_noperm_unlocked().
The new lookup_noperm_common() doesn't take a qstr yet. That will be
tidied up in a subsequent patch.
Signed-off-by: NeilBrown <neil@brown.name>
Link: https://lore.kernel.org/r/20250319031545.2999807-5-neil@brown.name
Signed-off-by: Christian Brauner <brauner@kernel.org>
Add the const qualifier to all the ctl_tables in the tree except for
watchdog_hardlockup_sysctl, memory_allocation_profiling_sysctls,
loadpin_sysctl_table and the ones calling register_net_sysctl (./net,
drivers/inifiniband dirs). These are special cases as they use a
registration function with a non-const qualified ctl_table argument or
modify the arrays before passing them on to the registration function.
Constifying ctl_table structs will prevent the modification of
proc_handler function pointers as the arrays would reside in .rodata.
This is made possible after commit 78eb4ea25c ("sysctl: treewide:
constify the ctl_table argument of proc_handlers") constified all the
proc_handlers.
Created this by running an spatch followed by a sed command:
Spatch:
virtual patch
@
depends on !(file in "net")
disable optional_qualifier
@
identifier table_name != {
watchdog_hardlockup_sysctl,
iwcm_ctl_table,
ucma_ctl_table,
memory_allocation_profiling_sysctls,
loadpin_sysctl_table
};
@@
+ const
struct ctl_table table_name [] = { ... };
sed:
sed --in-place \
-e "s/struct ctl_table .table = &uts_kern/const struct ctl_table *table = \&uts_kern/" \
kernel/utsname_sysctl.c
Reviewed-by: Song Liu <song@kernel.org>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org> # for kernel/trace/
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com> # SCSI
Reviewed-by: Darrick J. Wong <djwong@kernel.org> # xfs
Acked-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Corey Minyard <cminyard@mvista.com>
Acked-by: Wei Liu <wei.liu@kernel.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Bill O'Donnell <bodonnel@redhat.com>
Acked-by: Baoquan He <bhe@redhat.com>
Acked-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Acked-by: Anna Schumaker <anna.schumaker@oracle.com>
Signed-off-by: Joel Granados <joel.granados@kernel.org>
One of the paths quota writeback is called from is:
freeze_super()
sync_filesystem()
ext4_sync_fs()
dquot_writeback_dquots()
Since we currently don't always flush the quota_release_work queue in
this path, we can end up with the following race:
1. dquot are added to releasing_dquots list during regular operations.
2. FS Freeze starts, however, this does not flush the quota_release_work queue.
3. Freeze completes.
4. Kernel eventually tries to flush the workqueue while FS is frozen which
hits a WARN_ON since transaction gets started during frozen state:
ext4_journal_check_start+0x28/0x110 [ext4] (unreliable)
__ext4_journal_start_sb+0x64/0x1c0 [ext4]
ext4_release_dquot+0x90/0x1d0 [ext4]
quota_release_workfn+0x43c/0x4d0
Which is the following line:
WARN_ON(sb->s_writers.frozen == SB_FREEZE_COMPLETE);
Which ultimately results in generic/390 failing due to dmesg
noise. This was detected on powerpc machine 15 cores.
To avoid this, make sure to flush the workqueue during
dquot_writeback_dquots() so we dont have any pending workitems after
freeze.
Reported-by: Disha Goel <disgoel@linux.ibm.com>
CC: stable@vger.kernel.org
Fixes: dabc8b2075 ("quota: fix dqput() to follow the guarantees dquot_srcu should provide")
Reviewed-by: Baokun Li <libaokun1@huawei.com>
Signed-off-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20241121123855.645335-2-ojaswin@linux.ibm.com
Pull reiserfs removal from Jan Kara:
"The deprecation period of reiserfs is ending at the end of this year
so it is time to remove it"
* tag 'reiserfs_delete' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs:
reiserfs: The last commit
Pull quota and isofs updates from Jan Kara:
"Fix a memory leak in isofs and a cleanup of includes in quota"
* tag 'for_v6.13-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs:
dquot.c: get rid of include ../internal.h
isofs: avoid memory leak in iocharset
Deprecation period of reiserfs ends with the end of this year so it is
time to remove it from the kernel.
Acked-by: Darrick J. Wong <djwong@kernel.org>
Acked-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Pull quota and isofs updates from Jan Kara:
"A few small cleanups in quota and isofs"
* tag 'fs_for_v6.12-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs:
isofs: Annotate struct SL_component with __counted_by()
quota: remove unnecessary error code translation in dquot_quota_enable
quota: remove redundant return at end of void function
quota: remove unneeded return value of register_quota_format
quota: avoid missing put_quota_format when DQUOT_SUSPENDED is passed
For any changes of struct fd representation we need to
turn existing accesses to fields into calls of wrappers.
Accesses to struct fd::flags are very few (3 in linux/file.h,
1 in net/socket.c, 3 in fs/overlayfs/file.c and 3 more in
explicit initializers).
Those can be dealt with in the commit converting to
new layout; accesses to struct fd::file are too many for that.
This commit converts (almost) all of f.file to
fd_file(f). It's not entirely mechanical ('file' is used as
a member name more than just in struct fd) and it does not
even attempt to distinguish the uses in pointer context from
those in boolean context; the latter will be eventually turned
into a separate helper (fd_empty()).
NOTE: mass conversion to fd_empty(), tempting as it
might be, is a bad idea; better do that piecewise in commit
that convert from fdget...() to CLASS(...).
[conflicts in fs/fhandle.c, kernel/bpf/syscall.c, mm/memcontrol.c
caught by git; fs/stat.c one got caught by git grep]
[fs/xattr.c conflict]
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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>
Jan Kara
Linus Torvalds
Kees Cook
Al Viro
Abhishek BapatandJan Kara
Mateusz GuzikandChristian Brauner
Shashank A PandJan Kara
NeilBrownandChristian Brauner
Joel Granados
Ojaswin MujooandJan Kara
Joel Granados
Kemeng ShiandJan Kara
Chao YuandJan Kara