Re: [f2fs-dev] [PATCH v2] f2fs: quota: fix to avoid warning in dquot_writeback_dquots()

[Chao Yu via Linux-f2fs-devel <linux-f2fs-devel@lists.sourceforge.net>]

On 2025/2/8 00:24, Jaegeuk Kim wrote:
> It seems you need to remove dummy f2fs_quota_sync() in fs/f2fs/super.c to
> fix the build error.

It seems we need to replace f2fs_quota_sync() w/ f2fs_do_quota_sync().\,

 >> -int f2fs_quota_sync(struct super_block *sb, int type);
 >> +int f2fs_do_quota_sync(struct super_block *sb, int type);

since we changed exported function name.

Thanks,

> 
> 3204 int f2fs_quota_sync(struct super_block *sb, int type)
> 3205 {
> 3206         return 0;
> 3207 }
> 
> On 02/07, Chao Yu wrote:
>> F2FS-fs (dm-59): checkpoint=enable has some unwritten data.
>>
>> ------------[ cut here ]------------
>> WARNING: CPU: 6 PID: 8013 at fs/quota/dquot.c:691 dquot_writeback_dquots+0x2fc/0x308
>> pc : dquot_writeback_dquots+0x2fc/0x308
>> lr : f2fs_quota_sync+0xcc/0x1c4
>> Call trace:
>> dquot_writeback_dquots+0x2fc/0x308
>> f2fs_quota_sync+0xcc/0x1c4
>> f2fs_write_checkpoint+0x3d4/0x9b0
>> f2fs_issue_checkpoint+0x1bc/0x2c0
>> f2fs_sync_fs+0x54/0x150
>> f2fs_do_sync_file+0x2f8/0x814
>> __f2fs_ioctl+0x1960/0x3244
>> f2fs_ioctl+0x54/0xe0
>> __arm64_sys_ioctl+0xa8/0xe4
>> invoke_syscall+0x58/0x114
>>
>> checkpoint and f2fs_remount may race as below, resulting triggering warning
>> in dquot_writeback_dquots().
>>
>> atomic write                                    remount
>>                                                  - do_remount
>>                                                   - down_write(&sb->s_umount);
>>                                                    - f2fs_remount
>> - ioctl
>>   - f2fs_do_sync_file
>>    - f2fs_sync_fs
>>     - f2fs_write_checkpoint
>>      - block_operations
>>       - locked = down_read_trylock(&sbi->sb->s_umount)
>>         : fail to lock due to the write lock was held by remount
>>                                                   - up_write(&sb->s_umount);
>>       - f2fs_quota_sync
>>        - dquot_writeback_dquots
>>         - WARN_ON_ONCE(!rwsem_is_locked(&sb->s_umount))
>>         : trigger warning because s_umount lock was unlocked by remount
>>
>> If checkpoint comes from mount/umount/remount/freeze/quotactl, caller of
>> checkpoint has already held s_umount lock, calling dquot_writeback_dquots()
>> in the context should be safe.
>>
>> So let's record task to sbi->umount_lock_holder, so that checkpoint can
>> know whether the lock has held in the context or not by checking current
>> w/ it.
>>
>> In addition, in order to not misrepresent caller of checkpoint, we should
>> not allow to trigger async checkpoint for those callers: mount/umount/remount/
>> freeze/quotactl.
>>
>> Fixes: af033b2aa8a8 ("f2fs: guarantee journalled quota data by checkpoint")
>> Signed-off-by: Chao Yu <chao@kernel.org>
>> ---
>> v2:
>> - fix to return correct error number in f2fs_quota_on()
>> - clean up codes in block_operations()
>> - fix commit message
>>   fs/f2fs/checkpoint.c | 15 ++++++-----
>>   fs/f2fs/f2fs.h       |  3 ++-
>>   fs/f2fs/super.c      | 63 ++++++++++++++++++++++++++++++++++----------
>>   3 files changed, 60 insertions(+), 21 deletions(-)
>>
>> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
>> index efda9a022981..bd890738b94d 100644
>> --- a/fs/f2fs/checkpoint.c
>> +++ b/fs/f2fs/checkpoint.c
>> @@ -1237,7 +1237,7 @@ static int block_operations(struct f2fs_sb_info *sbi)
>>   retry_flush_quotas:
>>   	f2fs_lock_all(sbi);
>>   	if (__need_flush_quota(sbi)) {
>> -		int locked;
>> +		bool need_lock = sbi->umount_lock_holder != current;
>>   
>>   		if (++cnt > DEFAULT_RETRY_QUOTA_FLUSH_COUNT) {
>>   			set_sbi_flag(sbi, SBI_QUOTA_SKIP_FLUSH);
>> @@ -1246,11 +1246,13 @@ static int block_operations(struct f2fs_sb_info *sbi)
>>   		}
>>   		f2fs_unlock_all(sbi);
>>   
>> -		/* only failed during mount/umount/freeze/quotactl */
>> -		locked = down_read_trylock(&sbi->sb->s_umount);
>> -		f2fs_quota_sync(sbi->sb, -1);
>> -		if (locked)
>> +		/* don't grab s_umount lock during mount/umount/remount/freeze/quotactl */
>> +		if (!need_lock) {
>> +			f2fs_do_quota_sync(sbi->sb, -1);
>> +		} else if (down_read_trylock(&sbi->sb->s_umount)) {
>> +			f2fs_do_quota_sync(sbi->sb, -1);
>>   			up_read(&sbi->sb->s_umount);
>> +		}
>>   		cond_resched();
>>   		goto retry_flush_quotas;
>>   	}
>> @@ -1867,7 +1869,8 @@ int f2fs_issue_checkpoint(struct f2fs_sb_info *sbi)
>>   	struct cp_control cpc;
>>   
>>   	cpc.reason = __get_cp_reason(sbi);
>> -	if (!test_opt(sbi, MERGE_CHECKPOINT) || cpc.reason != CP_SYNC) {
>> +	if (!test_opt(sbi, MERGE_CHECKPOINT) || cpc.reason != CP_SYNC ||
>> +		sbi->umount_lock_holder == current) {
>>   		int ret;
>>   
>>   		f2fs_down_write(&sbi->gc_lock);
>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>> index bd0d8138b71d..205bdcbd01e6 100644
>> --- a/fs/f2fs/f2fs.h
>> +++ b/fs/f2fs/f2fs.h
>> @@ -1668,6 +1668,7 @@ struct f2fs_sb_info {
>>   
>>   	unsigned int nquota_files;		/* # of quota sysfile */
>>   	struct f2fs_rwsem quota_sem;		/* blocking cp for flags */
>> +	struct task_struct *umount_lock_holder;	/* s_umount lock holder */
>>   
>>   	/* # of pages, see count_type */
>>   	atomic_t nr_pages[NR_COUNT_TYPE];
>> @@ -3633,7 +3634,7 @@ int f2fs_inode_dirtied(struct inode *inode, bool sync);
>>   void f2fs_inode_synced(struct inode *inode);
>>   int f2fs_dquot_initialize(struct inode *inode);
>>   int f2fs_enable_quota_files(struct f2fs_sb_info *sbi, bool rdonly);
>> -int f2fs_quota_sync(struct super_block *sb, int type);
>> +int f2fs_do_quota_sync(struct super_block *sb, int type);
>>   loff_t max_file_blocks(struct inode *inode);
>>   void f2fs_quota_off_umount(struct super_block *sb);
>>   void f2fs_save_errors(struct f2fs_sb_info *sbi, unsigned char flag);
>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
>> index 24ded06c8980..944b09fd3aca 100644
>> --- a/fs/f2fs/super.c
>> +++ b/fs/f2fs/super.c
>> @@ -1738,22 +1738,28 @@ int f2fs_sync_fs(struct super_block *sb, int sync)
>>   
>>   static int f2fs_freeze(struct super_block *sb)
>>   {
>> +	struct f2fs_sb_info *sbi = F2FS_SB(sb);
>> +
>>   	if (f2fs_readonly(sb))
>>   		return 0;
>>   
>>   	/* IO error happened before */
>> -	if (unlikely(f2fs_cp_error(F2FS_SB(sb))))
>> +	if (unlikely(f2fs_cp_error(sbi)))
>>   		return -EIO;
>>   
>>   	/* must be clean, since sync_filesystem() was already called */
>> -	if (is_sbi_flag_set(F2FS_SB(sb), SBI_IS_DIRTY))
>> +	if (is_sbi_flag_set(sbi, SBI_IS_DIRTY))
>>   		return -EINVAL;
>>   
>> +	sbi->umount_lock_holder = current;
>> +
>>   	/* Let's flush checkpoints and stop the thread. */
>> -	f2fs_flush_ckpt_thread(F2FS_SB(sb));
>> +	f2fs_flush_ckpt_thread(sbi);
>> +
>> +	sbi->umount_lock_holder = NULL;
>>   
>>   	/* to avoid deadlock on f2fs_evict_inode->SB_FREEZE_FS */
>> -	set_sbi_flag(F2FS_SB(sb), SBI_IS_FREEZING);
>> +	set_sbi_flag(sbi, SBI_IS_FREEZING);
>>   	return 0;
>>   }
>>   
>> @@ -2330,6 +2336,8 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
>>   	org_mount_opt = sbi->mount_opt;
>>   	old_sb_flags = sb->s_flags;
>>   
>> +	sbi->umount_lock_holder = current;
>> +
>>   #ifdef CONFIG_QUOTA
>>   	org_mount_opt.s_jquota_fmt = F2FS_OPTION(sbi).s_jquota_fmt;
>>   	for (i = 0; i < MAXQUOTAS; i++) {
>> @@ -2553,6 +2561,8 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
>>   
>>   	limit_reserve_root(sbi);
>>   	*flags = (*flags & ~SB_LAZYTIME) | (sb->s_flags & SB_LAZYTIME);
>> +
>> +	sbi->umount_lock_holder = NULL;
>>   	return 0;
>>   restore_checkpoint:
>>   	if (need_enable_checkpoint) {
>> @@ -2593,6 +2603,8 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
>>   #endif
>>   	sbi->mount_opt = org_mount_opt;
>>   	sb->s_flags = old_sb_flags;
>> +
>> +	sbi->umount_lock_holder = NULL;
>>   	return err;
>>   }
>>   
>> @@ -2909,7 +2921,7 @@ static int f2fs_quota_sync_file(struct f2fs_sb_info *sbi, int type)
>>   	return ret;
>>   }
>>   
>> -int f2fs_quota_sync(struct super_block *sb, int type)
>> +int f2fs_do_quota_sync(struct super_block *sb, int type)
>>   {
>>   	struct f2fs_sb_info *sbi = F2FS_SB(sb);
>>   	struct quota_info *dqopt = sb_dqopt(sb);
>> @@ -2957,11 +2969,21 @@ int f2fs_quota_sync(struct super_block *sb, int type)
>>   	return ret;
>>   }
>>   
>> +static int f2fs_quota_sync(struct super_block *sb, int type)
>> +{
>> +	int ret;
>> +
>> +	F2FS_SB(sb)->umount_lock_holder = current;
>> +	ret = f2fs_do_quota_sync(sb, type);
>> +	F2FS_SB(sb)->umount_lock_holder = NULL;
>> +	return ret;
>> +}
>> +
>>   static int f2fs_quota_on(struct super_block *sb, int type, int format_id,
>>   							const struct path *path)
>>   {
>>   	struct inode *inode;
>> -	int err;
>> +	int err = 0;
>>   
>>   	/* if quota sysfile exists, deny enabling quota with specific file */
>>   	if (f2fs_sb_has_quota_ino(F2FS_SB(sb))) {
>> @@ -2972,31 +2994,34 @@ static int f2fs_quota_on(struct super_block *sb, int type, int format_id,
>>   	if (path->dentry->d_sb != sb)
>>   		return -EXDEV;
>>   
>> -	err = f2fs_quota_sync(sb, type);
>> +	F2FS_SB(sb)->umount_lock_holder = current;
>> +
>> +	err = f2fs_do_quota_sync(sb, type);
>>   	if (err)
>> -		return err;
>> +		goto out;
>>   
>>   	inode = d_inode(path->dentry);
>>   
>>   	err = filemap_fdatawrite(inode->i_mapping);
>>   	if (err)
>> -		return err;
>> +		goto out;
>>   
>>   	err = filemap_fdatawait(inode->i_mapping);
>>   	if (err)
>> -		return err;
>> +		goto out;
>>   
>>   	err = dquot_quota_on(sb, type, format_id, path);
>>   	if (err)
>> -		return err;
>> +		goto out;
>>   
>>   	inode_lock(inode);
>>   	F2FS_I(inode)->i_flags |= F2FS_QUOTA_DEFAULT_FL;
>>   	f2fs_set_inode_flags(inode);
>>   	inode_unlock(inode);
>>   	f2fs_mark_inode_dirty_sync(inode, false);
>> -
>> -	return 0;
>> +out:
>> +	F2FS_SB(sb)->umount_lock_holder = NULL;
>> +	return err;
>>   }
>>   
>>   static int __f2fs_quota_off(struct super_block *sb, int type)
>> @@ -3007,7 +3032,7 @@ static int __f2fs_quota_off(struct super_block *sb, int type)
>>   	if (!inode || !igrab(inode))
>>   		return dquot_quota_off(sb, type);
>>   
>> -	err = f2fs_quota_sync(sb, type);
>> +	err = f2fs_do_quota_sync(sb, type);
>>   	if (err)
>>   		goto out_put;
>>   
>> @@ -3030,6 +3055,8 @@ static int f2fs_quota_off(struct super_block *sb, int type)
>>   	struct f2fs_sb_info *sbi = F2FS_SB(sb);
>>   	int err;
>>   
>> +	F2FS_SB(sb)->umount_lock_holder = current;
>> +
>>   	err = __f2fs_quota_off(sb, type);
>>   
>>   	/*
>> @@ -3039,6 +3066,9 @@ static int f2fs_quota_off(struct super_block *sb, int type)
>>   	 */
>>   	if (is_journalled_quota(sbi))
>>   		set_sbi_flag(sbi, SBI_QUOTA_NEED_REPAIR);
>> +
>> +	F2FS_SB(sb)->umount_lock_holder = NULL;
>> +
>>   	return err;
>>   }
>>   
>> @@ -4704,6 +4734,7 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
>>   	if (err)
>>   		goto free_compress_inode;
>>   
>> +	sbi->umount_lock_holder = current;
>>   #ifdef CONFIG_QUOTA
>>   	/* Enable quota usage during mount */
>>   	if (f2fs_sb_has_quota_ino(sbi) && !f2fs_readonly(sb)) {
>> @@ -4830,6 +4861,8 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
>>   	f2fs_update_time(sbi, CP_TIME);
>>   	f2fs_update_time(sbi, REQ_TIME);
>>   	clear_sbi_flag(sbi, SBI_CP_DISABLED_QUICK);
>> +
>> +	sbi->umount_lock_holder = NULL;
>>   	return 0;
>>   
>>   sync_free_meta:
>> @@ -4932,6 +4965,8 @@ static void kill_f2fs_super(struct super_block *sb)
>>   	struct f2fs_sb_info *sbi = F2FS_SB(sb);
>>   
>>   	if (sb->s_root) {
>> +		sbi->umount_lock_holder = current;
>> +
>>   		set_sbi_flag(sbi, SBI_IS_CLOSE);
>>   		f2fs_stop_gc_thread(sbi);
>>   		f2fs_stop_discard_thread(sbi);
>> -- 
>> 2.48.1.502.g6dc24dfdaf-goog



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