btrfs: Add noinode_cache mount option

Add noinode_cache mount option for btrfs.

Since inode map cache involves all the btrfs_find_free_ino/return_ino
things and if just trigger the mount_opt,
an inode number get from inode map cache will not returned to inode map
cache.

To keep the find and return inode both in the same behavior,
a new bit in mount_opt, CHANGE_INODE_CACHE, is introduced for this idea.
CHANGE_INODE_CACHE is set/cleared in remounting, and the original
INODE_MAP_CACHE is set/cleared according to CHANGE_INODE_CACHE after a
success transaction.
Since find/return inode is all done between btrfs_start_transaction and
btrfs_commit_transaction, this will keep consistent behavior.

Also noinode_cache mount option will not stop the caching_kthread.

Cc: David Sterba <dsterba@suse.cz>
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>

fs/btrfs/ctree.h

@@ -2023,6 +2023,7 @@ 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)
 

fs/btrfs/disk-io.c

@@ -2776,6 +2776,10 @@ 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);
+
 #ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
 	if (btrfs_test_opt(tree_root, CHECK_INTEGRITY)) {
 		ret = btrfsic_mount(tree_root, fs_devices,

fs/btrfs/super.c

@@ -327,7 +327,7 @@ enum {
 	Opt_check_integrity_print_mask, Opt_fatal_errors, Opt_rescan_uuid_tree,
 	Opt_commit_interval, Opt_barrier, Opt_nodefrag, Opt_nodiscard,
 	Opt_noenospc_debug, Opt_noflushoncommit, Opt_acl, Opt_datacow,
-	Opt_datasum, Opt_treelog,
+	Opt_datasum, Opt_treelog, Opt_noinode_cache,
 	Opt_err,
 };
 
@@ -370,6 +370,7 @@ static match_table_t tokens = {
 	{Opt_defrag, "autodefrag"},
 	{Opt_nodefrag, "noautodefrag"},
 	{Opt_inode_cache, "inode_cache"},
+	{Opt_noinode_cache, "noinode_cache"},
 	{Opt_no_space_cache, "nospace_cache"},
 	{Opt_recovery, "recovery"},
 	{Opt_skip_balance, "skip_balance"},
@@ -627,7 +628,12 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 			break;
 		case Opt_inode_cache:
 			btrfs_info(root->fs_info, "enabling inode map caching");
-			btrfs_set_opt(info->mount_opt, INODE_MAP_CACHE);
+			btrfs_set_opt(info->mount_opt, CHANGE_INODE_CACHE);
+			break;
+		case Opt_noinode_cache:
+			if (btrfs_test_opt(root, CHANGE_INODE_CACHE))
+				btrfs_info(root->fs_info, "disabling inode map caching");
+			btrfs_clear_opt(info->mount_opt, CHANGE_INODE_CACHE);
 			break;
 		case Opt_clear_cache:
 			btrfs_info(root->fs_info, "force clearing of disk cache");

fs/btrfs/transaction.c

@@ -1826,6 +1826,15 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
 		goto cleanup_transaction;
 	}
 
+	/*
+	 * Since the transaction is done, we should set the inode map cache flag
+	 * before any other comming 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);
+
 	/* commit_fs_roots gets rid of all the tree log roots, it is now
 	 * safe to free the root of tree log roots
 	 */