thread 1:                        thread 2:
writeback                        checkpoint
set QUOTA_NEED_FLUSH
                                 clear QUOTA_NEED_FLUSH
f2fs_dquot_commit
dquot_commit
clear_dquot_dirty
                                 f2fs_quota_sync
                                 dquot_writeback_dquots
                                 nothing to commit
commit_dqblk
quota_write
f2fs_quota_write
waiting for f2fs_lock_op()
                                 pass __need_flush_quota
                                 (no F2FS_DIRTY_QDATA)

-> up-to-date quota is not written

Signed-off-by: Jaegeuk Kim <[email protected]>
---

v2 from v1:
 - avoid deadlock.
 - shorten the loop path

 fs/f2fs/checkpoint.c | 40 ++++++++++++++++++++--------------------
 fs/f2fs/f2fs.h       |  1 +
 fs/f2fs/super.c      | 27 ++++++++++++++++++++++-----
 3 files changed, 43 insertions(+), 25 deletions(-)

diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
index 89825261d474..66f29907fc0e 100644
--- a/fs/f2fs/checkpoint.c
+++ b/fs/f2fs/checkpoint.c
@@ -1131,17 +1131,26 @@ static void __prepare_cp_block(struct f2fs_sb_info *sbi)
 
 static bool __need_flush_quota(struct f2fs_sb_info *sbi)
 {
+       bool ret;
+
        if (!is_journalled_quota(sbi))
                return false;
-       if (is_sbi_flag_set(sbi, SBI_QUOTA_SKIP_FLUSH))
-               return false;
-       if (is_sbi_flag_set(sbi, SBI_QUOTA_NEED_REPAIR))
-               return false;
-       if (is_sbi_flag_set(sbi, SBI_QUOTA_NEED_FLUSH))
-               return true;
-       if (get_pages(sbi, F2FS_DIRTY_QDATA))
+
+       if (!down_write_trylock(&sbi->quota_sem))
                return true;
-       return false;
+
+       if (is_sbi_flag_set(sbi, SBI_QUOTA_SKIP_FLUSH))
+               ret = false;
+       else if (is_sbi_flag_set(sbi, SBI_QUOTA_NEED_REPAIR))
+               ret = false;
+       else if (is_sbi_flag_set(sbi, SBI_QUOTA_NEED_FLUSH))
+               ret = true;
+       else if (get_pages(sbi, F2FS_DIRTY_QDATA))
+               ret = true;
+       else
+               ret = false;
+       up_write(&sbi->quota_sem);
+       return ret;
 }
 
 /*
@@ -1160,14 +1169,16 @@ static int block_operations(struct f2fs_sb_info *sbi)
        blk_start_plug(&plug);
 
 retry_flush_quotas:
+       f2fs_lock_all(sbi);
        if (__need_flush_quota(sbi)) {
                int locked;
 
                if (++cnt > DEFAULT_RETRY_QUOTA_FLUSH_COUNT) {
                        set_sbi_flag(sbi, SBI_QUOTA_SKIP_FLUSH);
-                       f2fs_lock_all(sbi);
                        goto retry_flush_dents;
                }
+
+               f2fs_unlock_all(sbi);
                clear_sbi_flag(sbi, SBI_QUOTA_NEED_FLUSH);
 
                /* only failed during mount/umount/freeze/quotactl */
@@ -1175,11 +1186,6 @@ static int block_operations(struct f2fs_sb_info *sbi)
                f2fs_quota_sync(sbi->sb, -1);
                if (locked)
                        up_read(&sbi->sb->s_umount);
-       }
-
-       f2fs_lock_all(sbi);
-       if (__need_flush_quota(sbi)) {
-               f2fs_unlock_all(sbi);
                cond_resched();
                goto retry_flush_quotas;
        }
@@ -1201,12 +1207,6 @@ static int block_operations(struct f2fs_sb_info *sbi)
         */
        down_write(&sbi->node_change);
 
-       if (__need_flush_quota(sbi)) {
-               up_write(&sbi->node_change);
-               f2fs_unlock_all(sbi);
-               goto retry_flush_quotas;
-       }
-
        if (get_pages(sbi, F2FS_DIRTY_IMETA)) {
                up_write(&sbi->node_change);
                f2fs_unlock_all(sbi);
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 9b3d9977cd1e..692c0922f5b2 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1250,6 +1250,7 @@ struct f2fs_sb_info {
        block_t unusable_block_count;           /* # of blocks saved by last cp 
*/
 
        unsigned int nquota_files;              /* # of quota sysfile */
+       struct rw_semaphore quota_sem;          /* blocking cp for flags */
 
        /* # of pages, see count_type */
        atomic_t nr_pages[NR_COUNT_TYPE];
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 1dc02101e5e5..7a6d70d8e851 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -1946,7 +1946,10 @@ int f2fs_quota_sync(struct super_block *sb, int type)
        int cnt;
        int ret;
 
+       down_read(&sbi->quota_sem);
        ret = dquot_writeback_dquots(sb, type);
+       up_read(&sbi->quota_sem);
+
        if (ret)
                goto out;
 
@@ -2076,32 +2079,40 @@ static void f2fs_truncate_quota_inode_pages(struct 
super_block *sb)
 
 static int f2fs_dquot_commit(struct dquot *dquot)
 {
+       struct f2fs_sb_info *sbi = F2FS_SB(dquot->dq_sb);
        int ret;
 
+       down_read(&sbi->quota_sem);
        ret = dquot_commit(dquot);
        if (ret < 0)
-               set_sbi_flag(F2FS_SB(dquot->dq_sb), SBI_QUOTA_NEED_REPAIR);
+               set_sbi_flag(sbi, SBI_QUOTA_NEED_REPAIR);
+       up_read(&sbi->quota_sem);
        return ret;
 }
 
 static int f2fs_dquot_acquire(struct dquot *dquot)
 {
+       struct f2fs_sb_info *sbi = F2FS_SB(dquot->dq_sb);
        int ret;
 
+       down_read(&sbi->quota_sem);
        ret = dquot_acquire(dquot);
        if (ret < 0)
-               set_sbi_flag(F2FS_SB(dquot->dq_sb), SBI_QUOTA_NEED_REPAIR);
-
+               set_sbi_flag(sbi, SBI_QUOTA_NEED_REPAIR);
+       up_read(&sbi->quota_sem);
        return ret;
 }
 
 static int f2fs_dquot_release(struct dquot *dquot)
 {
+       struct f2fs_sb_info *sbi = F2FS_SB(dquot->dq_sb);
        int ret;
 
+       down_read(&sbi->quota_sem);
        ret = dquot_release(dquot);
        if (ret < 0)
-               set_sbi_flag(F2FS_SB(dquot->dq_sb), SBI_QUOTA_NEED_REPAIR);
+               set_sbi_flag(sbi, SBI_QUOTA_NEED_REPAIR);
+       up_read(&sbi->quota_sem);
        return ret;
 }
 
@@ -2111,22 +2122,27 @@ static int f2fs_dquot_mark_dquot_dirty(struct dquot 
*dquot)
        struct f2fs_sb_info *sbi = F2FS_SB(sb);
        int ret;
 
+       down_read(&sbi->quota_sem);
        ret = dquot_mark_dquot_dirty(dquot);
 
        /* if we are using journalled quota */
        if (is_journalled_quota(sbi))
                set_sbi_flag(sbi, SBI_QUOTA_NEED_FLUSH);
 
+       up_read(&sbi->quota_sem);
        return ret;
 }
 
 static int f2fs_dquot_commit_info(struct super_block *sb, int type)
 {
+       struct f2fs_sb_info *sbi = F2FS_SB(sb);
        int ret;
 
+       down_read(&sbi->quota_sem);
        ret = dquot_commit_info(sb, type);
        if (ret < 0)
-               set_sbi_flag(F2FS_SB(sb), SBI_QUOTA_NEED_REPAIR);
+               set_sbi_flag(sbi, SBI_QUOTA_NEED_REPAIR);
+       up_read(&sbi->quota_sem);
        return ret;
 }
 
@@ -3235,6 +3251,7 @@ static int f2fs_fill_super(struct super_block *sb, void 
*data, int silent)
        }
 
        init_rwsem(&sbi->cp_rwsem);
+       init_rwsem(&sbi->quota_sem);
        init_waitqueue_head(&sbi->cp_wait);
        init_sb_info(sbi);
 
-- 
2.19.0.605.g01d371f741-goog

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