btrfs: switch inode_cache option handling to pending changes

The pending mount option(s) now share namespace and bits with the normal
options, and the existing one for (inode_cache) is unset unconditionally
at each transaction commit.

Introduce a separate namespace for pending changes and enhance the
descriptions of the intended change to use separate bits for each
action.

Signed-off-by: David Sterba <dsterba@suse.cz>

fs/btrfs/ctree.h

@@ -2098,7 +2098,6 @@ struct btrfs_ioctl_defrag_range_args {
 #define BTRFS_MOUNT_CHECK_INTEGRITY_INCLUDING_EXTENT_DATA (1 << 21)
 #define BTRFS_MOUNT_PANIC_ON_FATAL_ERROR	(1 << 22)
 #define BTRFS_MOUNT_RESCAN_UUID_TREE	(1 << 23)
-#define	BTRFS_MOUNT_CHANGE_INODE_CACHE	(1 << 24)
 
 #define BTRFS_DEFAULT_COMMIT_INTERVAL	(30)
 #define BTRFS_DEFAULT_MAX_INLINE	(8192)
@@ -2131,6 +2130,9 @@ struct btrfs_ioctl_defrag_range_args {
  * transaction commit)
  */
 
+#define BTRFS_PENDING_SET_INODE_MAP_CACHE	(0)
+#define BTRFS_PENDING_CLEAR_INODE_MAP_CACHE	(1)
+
 #define btrfs_test_pending(info, opt)	\
 	test_bit(BTRFS_PENDING_##opt, &(info)->pending_changes)
 #define btrfs_set_pending(info, opt)	\

fs/btrfs/disk-io.c

@@ -2830,10 +2830,6 @@ retry_root_backup:
 		btrfs_set_opt(fs_info->mount_opt, SSD);
 	}
 
-	/* Set the real inode map cache flag */
-	if (btrfs_test_opt(tree_root, CHANGE_INODE_CACHE))
-		btrfs_set_opt(tree_root->fs_info->mount_opt, INODE_MAP_CACHE);
-
 	/*
 	 * Mount does not set all options immediatelly, we can do it now and do
 	 * not have to wait for transaction commit

fs/btrfs/inode-map.c

@@ -178,7 +178,7 @@ static void start_caching(struct btrfs_root *root)
 			  root->root_key.objectid);
 	if (IS_ERR(tsk)) {
 		btrfs_warn(root->fs_info, "failed to start inode caching task");
-		btrfs_clear_and_info(root, CHANGE_INODE_CACHE,
+		btrfs_clear_pending_and_info(root->fs_info, INODE_MAP_CACHE,
 				"disabling inode map caching");
 	}
 }

fs/btrfs/super.c

@@ -642,11 +642,11 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 					     "disabling disk space caching");
 			break;
 		case Opt_inode_cache:
-			btrfs_set_and_info(root, CHANGE_INODE_CACHE,
+			btrfs_set_pending_and_info(info, INODE_MAP_CACHE,
 					   "enabling inode map caching");
 			break;
 		case Opt_noinode_cache:
-			btrfs_clear_and_info(root, CHANGE_INODE_CACHE,
+			btrfs_clear_pending_and_info(info, INODE_MAP_CACHE,
 					     "disabling inode map caching");
 			break;
 		case Opt_clear_cache:

fs/btrfs/transaction.c

@@ -1842,14 +1842,9 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
 	}
 
 	/*
-	 * Since the transaction is done, we should set the inode map cache flag
-	 * before any other comming transaction.
+	 * Since the transaction is done, we can apply the pending changes
+	 * before the next transaction.
 	 */
-	if (btrfs_test_opt(root, CHANGE_INODE_CACHE))
-		btrfs_set_opt(root->fs_info->mount_opt, INODE_MAP_CACHE);
-	else
-		btrfs_clear_opt(root->fs_info->mount_opt, INODE_MAP_CACHE);
-
 	btrfs_apply_pending_changes(root->fs_info);
 
 	/* commit_fs_roots gets rid of all the tree log roots, it is now
@@ -2031,6 +2026,16 @@ void btrfs_apply_pending_changes(struct btrfs_fs_info *fs_info)
 	if (!prev)
 		return;
 
+	bit = 1 << BTRFS_PENDING_SET_INODE_MAP_CACHE;
+	if (prev & bit)
+		btrfs_set_opt(fs_info->mount_opt, INODE_MAP_CACHE);
+	prev &= ~bit;
+
+	bit = 1 << BTRFS_PENDING_CLEAR_INODE_MAP_CACHE;
+	if (prev & bit)
+		btrfs_clear_opt(fs_info->mount_opt, INODE_MAP_CACHE);
+	prev &= ~bit;
+
 	if (prev)
 		btrfs_warn(fs_info,
 			"unknown pending changes left 0x%lx, ignoring", prev);