Commit b0feb9d9 authored by Miao Xie's avatar Miao Xie Committed by Josef Bacik
Browse files

Btrfs: introduce grab/put functions for the root of the fs/file tree 



The grab/put funtions will be used in the next patch, which need grab
the root object and ensure it is not freed. We use reference counter
instead of the srcu lock is to aovid blocking the memory reclaim task,
which invokes synchronize_srcu().

Signed-off-by: default avatarMiao Xie <miaox@cn.fujitsu.com>
Signed-off-by: default avatarJosef Bacik <jbacik@fusionio.com>
parent cb517eab

fs/btrfs/ctree.h

+1 −0
Original line number Diff line number Diff line
@@ -1746,6 +1746,7 @@ struct btrfs_root { 
	int force_cow;



	spinlock_t root_item_lock;

	atomic_t refs;

};



struct btrfs_ioctl_defrag_range_args {

fs/btrfs/disk-io.c

+3 −2
Original line number Diff line number Diff line
@@ -1216,6 +1216,7 @@ static void __setup_root(u32 nodesize, u32 leafsize, u32 sectorsize, 
	atomic_set(&root->log_writers, 0);

	atomic_set(&root->log_batch, 0);

	atomic_set(&root->orphan_inodes, 0);

	atomic_set(&root->refs, 1);

	root->log_transid = 0;

	root->last_log_commit = 0;

	extent_io_tree_init(&root->dirty_log_pages,
@@ -2052,7 +2053,7 @@ static void del_fs_roots(struct btrfs_fs_info *fs_info) 
		} else {

			free_extent_buffer(gang[0]->node);

			free_extent_buffer(gang[0]->commit_root);

			kfree(gang[0]);

			btrfs_put_fs_root(gang[0]);

		}

	}
@@ -3417,7 +3418,7 @@ static void free_fs_root(struct btrfs_root *root) 
	kfree(root->free_ino_ctl);

	kfree(root->free_ino_pinned);

	kfree(root->name);

	kfree(root);

	btrfs_put_fs_root(root);

}



void btrfs_free_fs_root(struct btrfs_root *root)

fs/btrfs/disk-io.h

+21 −0
Original line number Diff line number Diff line
@@ -76,6 +76,27 @@ void btrfs_btree_balance_dirty_nodelay(struct btrfs_root *root); 
void btrfs_drop_and_free_fs_root(struct btrfs_fs_info *fs_info,

				 struct btrfs_root *root);

void btrfs_free_fs_root(struct btrfs_root *root);



/*

 * This function is used to grab the root, and avoid it is freed when we

 * access it. But it doesn't ensure that the tree is not dropped.

 *

 * If you want to ensure the whole tree is safe, you should use

 * 	fs_info->subvol_srcu

 */

static inline struct btrfs_root *btrfs_grab_fs_root(struct btrfs_root *root)

{

	if (atomic_inc_not_zero(&root->refs))

		return root;

	return NULL;

}



static inline void btrfs_put_fs_root(struct btrfs_root *root)

{

	if (atomic_dec_and_test(&root->refs))

		kfree(root);

}



void btrfs_mark_buffer_dirty(struct extent_buffer *buf);

int btrfs_buffer_uptodate(struct extent_buffer *buf, u64 parent_transid,

			  int atomic);

fs/btrfs/extent-tree.c

+1 −1
Original line number Diff line number Diff line
@@ -7469,7 +7469,7 @@ int btrfs_drop_snapshot(struct btrfs_root *root, 
	} else {

		free_extent_buffer(root->node);

		free_extent_buffer(root->commit_root);

		kfree(root);

		btrfs_put_fs_root(root);

	}

out_end_trans:

	btrfs_end_transaction_throttle(trans, tree_root);

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