kernel/linux.git/fs/quota, branch v6.12.80

quota: fix livelock between quotactl and freeze_super

2026-03-04T12:20:00+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

fs: quota: create dedicated workqueue for quota_release_work

2025-10-19T14:33:49+00:00

commit 72b7ceca857f38a8ca7c5629feffc63769638974 upstream. 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 Signed-off-by: Greg Kroah-Hartman

quota: flush quota_release_work upon quota writeback

2024-12-09T09:40:55+00:00

[ Upstream commit ac6f420291b3fee1113f21d612fa88b628afab5b ] 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 Signed-off-by: Sasha Levin

Merge tag 'fs_for_v6.12-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs

2024-09-23T17:49:28+00:00

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

introduce fd_file(), convert all accessors to it.

2024-08-13T02:00:43+00:00

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 Signed-off-by: Al Viro

sysctl: treewide: constify the ctl_table argument of proc_handlers

2024-07-24T18:59:29+00:00

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 Signed-off-by: Thomas Weißschuh Co-developed-by: Joel Granados Signed-off-by: Joel Granados

quota: remove unnecessary error code translation in dquot_quota_enable

2024-07-22T16:13:56+00:00

Simply set error code to -EEXIST when quota limit is already enabled in dquot_quota_enable to remove unnecessary error code translation. Link: https://patch.msgid.link/20240715130534.2112678-5-shikemeng@huaweicloud.com Signed-off-by: Kemeng Shi Signed-off-by: Jan Kara

quota: remove redundant return at end of void function

2024-07-22T16:13:50+00:00

Function dquot_claim_space_nodirty nad dquot_reclaim_space_nodirty have no return value, just remove redundant return at end of the functions. Link: https://patch.msgid.link/20240715130534.2112678-4-shikemeng@huaweicloud.com Signed-off-by: Kemeng Shi Signed-off-by: Jan Kara

quota: remove unneeded return value of register_quota_format

2024-07-22T16:13:44+00:00

The register_quota_format always returns 0, simply remove unneeded return value. Link: https://patch.msgid.link/20240715130534.2112678-3-shikemeng@huaweicloud.com Signed-off-by: Kemeng Shi Reviewed-by: Joseph Qi Signed-off-by: Jan Kara

quota: avoid missing put_quota_format when DQUOT_SUSPENDED is passed

2024-07-22T16:13:34+00:00

Avoid missing put_quota_format when DQUOT_SUSPENDED is passed to dquot_load_quota_sb. Link: https://patch.msgid.link/20240715130534.2112678-2-shikemeng@huaweicloud.com Signed-off-by: Kemeng Shi Fixes: d44c57663723 ("quota: Remove BUG_ON in dquot_load_quota_sb()") Reviewed-by: Joseph Qi Signed-off-by: Jan Kara