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f2fs: quota: fix to avoid warning in dquot_writeback_dquots()
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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: af033b2 ("f2fs: guarantee journalled quota data by checkpoint")
Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
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Chao Yu authored and Jaegeuk Kim committed Feb 10, 2025
1 parent 53333cd commit eb85c24
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Showing 3 changed files with 61 additions and 22 deletions.
15 changes: 9 additions & 6 deletions fs/f2fs/checkpoint.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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);
Expand All @@ -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;
}
Expand Down Expand Up @@ -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);
Expand Down
3 changes: 2 additions & 1 deletion fs/f2fs/f2fs.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1659,6 +1659,7 @@ 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];
Expand Down Expand Up @@ -3624,7 +3625,7 @@ 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);
Expand Down
65 changes: 50 additions & 15 deletions fs/f2fs/super.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1737,22 +1737,28 @@ 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;
}

Expand Down Expand Up @@ -2329,6 +2335,8 @@ 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++) {
Expand Down Expand Up @@ -2552,6 +2560,8 @@ 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) {
Expand Down Expand Up @@ -2592,6 +2602,8 @@ 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;
}

Expand Down Expand Up @@ -2908,7 +2920,7 @@ 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);
Expand Down Expand Up @@ -2956,11 +2968,21 @@ 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))) {
Expand All @@ -2971,31 +2993,34 @@ 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)
Expand All @@ -3006,7 +3031,7 @@ 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;

Expand All @@ -3029,6 +3054,8 @@ 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);

/*
Expand All @@ -3038,6 +3065,9 @@ 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;
}

Expand Down Expand Up @@ -3170,7 +3200,7 @@ int f2fs_dquot_initialize(struct inode *inode)
return 0;
}

int f2fs_quota_sync(struct super_block *sb, int type)
int f2fs_do_quota_sync(struct super_block *sb, int type)
{
return 0;
}
Expand Down Expand Up @@ -4703,6 +4733,7 @@ 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)) {
Expand Down Expand Up @@ -4829,6 +4860,8 @@ 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:
Expand Down Expand Up @@ -4931,6 +4964,8 @@ 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);
Expand Down

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