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

quota: fix livelock between quotactl and freeze_super

2026-02-26T23:01:06+00:00

[ Upstream commit 77449e453dfc006ad738dec55374c4cbc056fd39 ] 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: 576215cffdef ("fs: Drop wait_unfrozen wait queue") Signed-off-by: Abhishek Bapat Link: https://patch.msgid.link/20260115213103.1089129-1-abhishekbapat@google.com Signed-off-by: Jan Kara Signed-off-by: Sasha Levin

Coccinelle-based conversion to use ->i_state accessors

2025-10-20T18:22:26+00:00

All places were patched by coccinelle with the default expecting that ->i_lock is held, afterwards entries got fixed up by hand to use unlocked variants as needed. The script: @@ expression inode, flags; @@ - inode->i_state & flags + inode_state_read(inode) & flags @@ expression inode, flags; @@ - inode->i_state &= ~flags + inode_state_clear(inode, flags) @@ expression inode, flag1, flag2; @@ - inode->i_state &= ~flag1 & ~flag2 + inode_state_clear(inode, flag1 | flag2) @@ expression inode, flags; @@ - inode->i_state |= flags + inode_state_set(inode, flags) @@ expression inode, flags; @@ - inode->i_state = flags + inode_state_assign(inode, flags) @@ expression inode, flags; @@ - flags = inode->i_state + flags = inode_state_read(inode) @@ expression inode, flags; @@ - READ_ONCE(inode->i_state) & flags + inode_state_read(inode) & flags Signed-off-by: Mateusz Guzik Signed-off-by: Christian Brauner

fs: quota: create dedicated workqueue for quota_release_work

2025-09-03T10:35:00+00:00

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: ac6f420291b3 ("quota: flush quota_release_work upon quota writeback") CC: stable@vger.kernel.org Signed-off-by: Shashank A P Link: https://patch.msgid.link/20250901092905.2115-1-shashank.ap@samsung.com Signed-off-by: Jan Kara

VFS: rename lookup_one_len family to lookup_noperm and remove permission check

2025-04-08T09:24:36+00:00

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 Link: https://lore.kernel.org/r/20250319031545.2999807-5-neil@brown.name Signed-off-by: Christian Brauner

treewide: const qualify ctl_tables where applicable

2025-01-28T12:48:37+00:00

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 78eb4ea25cd5 ("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 Acked-by: Steven Rostedt (Google) # for kernel/trace/ Reviewed-by: Martin K. Petersen # SCSI Reviewed-by: Darrick J. Wong # xfs Acked-by: Jani Nikula Acked-by: Corey Minyard Acked-by: Wei Liu Acked-by: Thomas Gleixner Reviewed-by: Bill O'Donnell Acked-by: Baoquan He Acked-by: Ashutosh Dixit Acked-by: Anna Schumaker Signed-off-by: Joel Granados

quota: flush quota_release_work upon quota writeback

2024-11-26T21:54:00+00:00

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 CC: stable@vger.kernel.org Fixes: dabc8b207566 ("quota: fix dqput() to follow the guarantees dquot_srcu should provide") Reviewed-by: Baokun Li Signed-off-by: Ojaswin Mujoo Signed-off-by: Jan Kara Link: https://patch.msgid.link/20241121123855.645335-2-ojaswin@linux.ibm.com

Merge tag 'reiserfs_delete' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs

2024-11-21T17:50:18+00:00

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

Merge tag 'for_v6.13-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs

2024-11-21T17:47:44+00:00

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

dquot.c: get rid of include ../internal.h

2024-11-13T14:24:08+00:00

Ugh, indeed - and not needed nearly a decade. It had been added for the sake of inode_sb_list_lock and that spinlock had become a per-superblock (->s_inode_list_lock) in March 2015... Signed-off-by: Al Viro Signed-off-by: Jan Kara Link: https://patch.msgid.link/20241112213842.GC3387508@ZenIV

fdget_raw() users: switch to CLASS(fd_raw)

2024-11-03T06:28:06+00:00

Reviewed-by: Christian Brauner Signed-off-by: Al Viro