kernel/linux.git/fs/quota, branch v6.6.134

quota: fix livelock between quotactl and freeze_super

2026-03-04T12:19:44+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

2025-10-23T14:16:41+00:00

[ Upstream commit 72b7ceca857f38a8ca7c5629feffc63769638974 ] 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: Sasha Levin Signed-off-by: Greg Kroah-Hartman

quota: remove unneeded return value of register_quota_format

2025-10-23T14:16:41+00:00

[ Upstream commit a838e5dca63d1dc701e63b2b1176943c57485c45 ] 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 Stable-dep-of: 72b7ceca857f ("fs: quota: create dedicated workqueue for quota_release_work") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

quota: flush quota_release_work upon quota writeback

2024-12-09T09:33:01+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

quota: Remove BUG_ON from dqget()

2024-08-29T15:33:33+00:00

[ Upstream commit 249f374eb9b6b969c64212dd860cc1439674c4a8 ] dqget() checks whether dquot->dq_sb is set when returning it using BUG_ON. Firstly this doesn't work as an invalidation check for quite some time (we release dquot with dq_sb set these days), secondly using BUG_ON is quite harsh. Use WARN_ON_ONCE and check whether dquot is still hashed instead. Signed-off-by: Jan Kara Signed-off-by: Sasha Levin

quota: Detect loops in quota tree

2024-08-19T04:04:27+00:00

[ Upstream commit a898cb621ac589b0b9e959309689a027e765aa12 ] Syzbot has found that when it creates corrupted quota files where the quota tree contains a loop, we will deadlock when tryling to insert a dquot. Add loop detection into functions traversing the quota tree. Signed-off-by: Jan Kara Signed-off-by: Sasha Levin

quota: Properly annotate i_dquot arrays with __rcu

2024-03-26T22:19:46+00:00

[ Upstream commit ccb49011bb2ebfd66164dbf68c5bff48917bb5ef ] Dquots pointed to from i_dquot arrays in inodes are protected by dquot_srcu. Annotate them as such and change .get_dquots callback to return properly annotated pointer to make sparse happy. Fixes: b9ba6f94b238 ("quota: remove dqptr_sem") Signed-off-by: Jan Kara Signed-off-by: Sasha Levin

quota: Fix rcu annotations of inode dquot pointers

2024-03-26T22:19:46+00:00

[ Upstream commit 179b8c97ebf63429589f5afeba59a181fe70603e ] Dquot pointers in i_dquot array in the inode are protected by dquot_srcu. Annotate the array pointers with __rcu, perform the locked dereferences with srcu_dereference_check() instead of plain reads, and set the array elements with rcu_assign_pointer(). Fixes: b9ba6f94b238 ("quota: remove dqptr_sem") Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202402061900.rTuYDlo6-lkp@intel.com/ Signed-off-by: Jan Kara Signed-off-by: Sasha Levin

quota: Fix potential NULL pointer dereference

2024-03-26T22:19:46+00:00

[ Upstream commit d0aa72604fbd80c8aabb46eda00535ed35570f1f ] Below race may cause NULL pointer dereference P1 P2 dquot_free_inode quota_off drop_dquot_ref remove_dquot_ref dquots = i_dquot(inode) dquots = i_dquot(inode) srcu_read_lock dquots[cnt]) != NULL (1) dquots[type] = NULL (2) spin_lock(&dquots[cnt]->dq_dqb_lock) (3) .... If dquot_free_inode(or other routines) checks inode's quota pointers (1) before quota_off sets it to NULL(2) and use it (3) after that, NULL pointer dereference will be triggered. So let's fix it by using a temporary pointer to avoid this issue. Signed-off-by: Wang Jianjian Signed-off-by: Jan Kara Message-Id: <20240202081852.2514092-1-wangjianjian3@huawei.com> Stable-dep-of: 179b8c97ebf6 ("quota: Fix rcu annotations of inode dquot pointers") Signed-off-by: Sasha Levin

quota: explicitly forbid quota files from being encrypted

2023-11-28T17:20:04+00:00

commit d3cc1b0be258191d6360c82ea158c2972f8d3991 upstream. Since commit d7e7b9af104c ("fscrypt: stop using keyrings subsystem for fscrypt_master_key"), xfstest generic/270 causes a WARNING when run on f2fs with test_dummy_encryption in the mount options: $ kvm-xfstests -c f2fs/encrypt generic/270 [...] WARNING: CPU: 1 PID: 2453 at fs/crypto/keyring.c:240 fscrypt_destroy_keyring+0x1f5/0x260 The cause of the WARNING is that not all encrypted inodes have been evicted before fscrypt_destroy_keyring() is called, which violates an assumption. This happens because the test uses an external quota file, which gets automatically encrypted due to test_dummy_encryption. Encryption of quota files has never really been supported. On ext4, ext4_quota_read() does not decrypt the data, so encrypted quota files are always considered invalid on ext4. On f2fs, f2fs_quota_read() uses the pagecache, so trying to use an encrypted quota file gets farther, resulting in the issue described above being possible. But this was never intended to be possible, and there is no use case for it. Therefore, make the quota support layer explicitly reject using IS_ENCRYPTED inodes when quotaon is attempted. Cc: stable@vger.kernel.org Signed-off-by: Eric Biggers Signed-off-by: Jan Kara Message-Id: <20230905003227.326998-1-ebiggers@kernel.org> Signed-off-by: Greg Kroah-Hartman