f2fs: change to use rwsem for cp_mutex

Use rwsem to ensure serialization of the callers and to avoid
starvation of high priority tasks, when the system is under
heavy IO workload.
Signed-off-by: NSahitya Tummala <stummala@codeaurora.org>
Reviewed-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/checkpoint.c

@@ -348,13 +348,13 @@ static int f2fs_write_meta_pages(struct address_space *mapping,
 		goto skip_write;
 
 	/* if locked failed, cp will flush dirty pages instead */
-	if (!mutex_trylock(&sbi->cp_mutex))
+	if (!down_write_trylock(&sbi->cp_global_sem))
 		goto skip_write;
 
 	trace_f2fs_writepages(mapping->host, wbc, META);
 	diff = nr_pages_to_write(sbi, META, wbc);
 	written = f2fs_sync_meta_pages(sbi, META, wbc->nr_to_write, FS_META_IO);
-	mutex_unlock(&sbi->cp_mutex);
+	up_write(&sbi->cp_global_sem);
 	wbc->nr_to_write = max((long)0, wbc->nr_to_write - written - diff);
 	return 0;
 
@@ -1572,7 +1572,7 @@ int f2fs_write_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
 		f2fs_warn(sbi, "Start checkpoint disabled!");
 	}
 	if (cpc->reason != CP_RESIZE)
-		mutex_lock(&sbi->cp_mutex);
+		down_write(&sbi->cp_global_sem);
 
 	if (!is_sbi_flag_set(sbi, SBI_IS_DIRTY) &&
 		((cpc->reason & CP_FASTBOOT) || (cpc->reason & CP_SYNC) ||
@@ -1647,7 +1647,7 @@ int f2fs_write_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
 	trace_f2fs_write_checkpoint(sbi->sb, cpc->reason, "finish checkpoint");
 out:
 	if (cpc->reason != CP_RESIZE)
-		mutex_unlock(&sbi->cp_mutex);
+		up_write(&sbi->cp_global_sem);
 	return err;
 }
 

fs/f2fs/f2fs.h

@@ -1369,7 +1369,7 @@ struct f2fs_sb_info {
 	int cur_cp_pack;			/* remain current cp pack */
 	spinlock_t cp_lock;			/* for flag in ckpt */
 	struct inode *meta_inode;		/* cache meta blocks */
-	struct mutex cp_mutex;			/* checkpoint procedure lock */
+	struct rw_semaphore cp_global_sem;	/* checkpoint procedure lock */
 	struct rw_semaphore cp_rwsem;		/* blocking FS operations */
 	struct rw_semaphore node_write;		/* locking node writes */
 	struct rw_semaphore node_change;	/* locking node change */

fs/f2fs/gc.c

@@ -1986,7 +1986,7 @@ int f2fs_resize_fs(struct f2fs_sb_info *sbi, __u64 block_count)
 
 	freeze_super(sbi->sb);
 	down_write(&sbi->gc_lock);
-	mutex_lock(&sbi->cp_mutex);
+	down_write(&sbi->cp_global_sem);
 
 	spin_lock(&sbi->stat_lock);
 	if (shrunk_blocks + valid_user_blocks(sbi) +
@@ -2031,7 +2031,7 @@ int f2fs_resize_fs(struct f2fs_sb_info *sbi, __u64 block_count)
 		spin_unlock(&sbi->stat_lock);
 	}
 out_err:
-	mutex_unlock(&sbi->cp_mutex);
+	up_write(&sbi->cp_global_sem);
 	up_write(&sbi->gc_lock);
 	thaw_super(sbi->sb);
 	clear_sbi_flag(sbi, SBI_IS_RESIZEFS);

fs/f2fs/recovery.c

@@ -799,7 +799,7 @@ int f2fs_recover_fsync_data(struct f2fs_sb_info *sbi, bool check_only)
 	INIT_LIST_HEAD(&dir_list);
 
 	/* prevent checkpoint */
-	mutex_lock(&sbi->cp_mutex);
+	down_write(&sbi->cp_global_sem);
 
 	/* step #1: find fsynced inode numbers */
 	err = find_fsync_dnodes(sbi, &inode_list, check_only);
@@ -850,7 +850,7 @@ int f2fs_recover_fsync_data(struct f2fs_sb_info *sbi, bool check_only)
 	if (!err)
 		clear_sbi_flag(sbi, SBI_POR_DOING);
 
-	mutex_unlock(&sbi->cp_mutex);
+	up_write(&sbi->cp_global_sem);
 
 	/* let's drop all the directory inodes for clean checkpoint */
 	destroy_fsync_dnodes(&dir_list, err);

fs/f2fs/super.c

@@ -3551,7 +3551,7 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
 	sbi->valid_super_block = valid_super_block;
 	init_rwsem(&sbi->gc_lock);
 	mutex_init(&sbi->writepages);
-	mutex_init(&sbi->cp_mutex);
+	init_rwsem(&sbi->cp_global_sem);
 	init_rwsem(&sbi->node_write);
 	init_rwsem(&sbi->node_change);