f2fs: introduce a new global lock scheme

In the previous version, f2fs uses global locks according to the usage types,
such as directory operations, block allocation, block write, and so on.

Reference the following lock types in f2fs.h.
enum lock_type {
	RENAME,		/* for renaming operations */
	DENTRY_OPS,	/* for directory operations */
	DATA_WRITE,	/* for data write */
	DATA_NEW,	/* for data allocation */
	DATA_TRUNC,	/* for data truncate */
	NODE_NEW,	/* for node allocation */
	NODE_TRUNC,	/* for node truncate */
	NODE_WRITE,	/* for node write */
	NR_LOCK_TYPE,
};

In that case, we lose the performance under the multi-threading environment,
since every types of operations must be conducted one at a time.

In order to address the problem, let's share the locks globally with a mutex
array regardless of any types.
So, let users grab a mutex and perform their jobs in parallel as much as
possbile.

For this, I propose a new global lock scheme as follows.

0. Data structure
 - f2fs_sb_info -> mutex_lock[NR_GLOBAL_LOCKS]
 - f2fs_sb_info -> node_write

1. mutex_lock_op(sbi)
 - try to get an avaiable lock from the array.
 - returns the index of the gottern lock variable.

2. mutex_unlock_op(sbi, index of the lock)
 - unlock the given index of the lock.

3. mutex_lock_all(sbi)
 - grab all the locks in the array before the checkpoint.

4. mutex_unlock_all(sbi)
 - release all the locks in the array after checkpoint.

5. block_operations()
 - call mutex_lock_all()
 - sync_dirty_dir_inodes()
 - grab node_write
 - sync_node_pages()

Note that,
 the pairs of mutex_lock_op()/mutex_unlock_op() and
 mutex_lock_all()/mutex_unlock_all() should be used together.

Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

1 files changed, 12 insertions, 27 deletions

diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
index 93fd57d491ac..be6aa2eef894 100644
--- a/fs/f2fs/checkpoint.c
+++ b/fs/f2fs/checkpoint.c
@@ -543,54 +543,39 @@ retry:
  */
 static void block_operations(struct f2fs_sb_info *sbi)
 {
-        int t;
         struct writeback_control wbc = {
                 .sync_mode = WB_SYNC_ALL,
                 .nr_to_write = LONG_MAX,
                 .for_reclaim = 0,
         };
+retry_flush_dents:
+        mutex_lock_all(sbi);
 
-        /* Stop renaming operation */
-        mutex_lock_op(sbi, RENAME);
-        mutex_lock_op(sbi, DENTRY_OPS);
-
-retry_dents:
         /* write all the dirty dentry pages */
-        sync_dirty_dir_inodes(sbi);
-
-        mutex_lock_op(sbi, DATA_WRITE);
         if (get_pages(sbi, F2FS_DIRTY_DENTS)) {
-                mutex_unlock_op(sbi, DATA_WRITE);
-                goto retry_dents;
+                mutex_unlock_all(sbi);
+                sync_dirty_dir_inodes(sbi);
+                goto retry_flush_dents;
         }
 
-        /* block all the operations */
-        for (t = DATA_NEW; t <= NODE_TRUNC; t++)
-                mutex_lock_op(sbi, t);
-
-        mutex_lock(&sbi->write_inode);
-
         /*
          * POR: we should ensure that there is no dirty node pages
          * until finishing nat/sit flush.
          */
-retry:
-        sync_node_pages(sbi, 0, &wbc);
-
-        mutex_lock_op(sbi, NODE_WRITE);
+retry_flush_nodes:
+        mutex_lock(&sbi->node_write);
 
         if (get_pages(sbi, F2FS_DIRTY_NODES)) {
-                mutex_unlock_op(sbi, NODE_WRITE);
-                goto retry;
+                mutex_unlock(&sbi->node_write);
+                sync_node_pages(sbi, 0, &wbc);
+                goto retry_flush_nodes;
         }
-        mutex_unlock(&sbi->write_inode);
 }
 
 static void unblock_operations(struct f2fs_sb_info *sbi)
 {
-        int t;
-        for (t = NODE_WRITE; t >= RENAME; t--)
-                mutex_unlock_op(sbi, t);
+        mutex_unlock(&sbi->node_write);
+        mutex_unlock_all(sbi);
 }
 
 static void do_checkpoint(struct f2fs_sb_info *sbi, bool is_umount)