f2fs: fix race condition in between free nid allocator/initializer
commit 30a61ddf8117c26ac5b295e1233eaa9629a94ca3 upstream.
In below concurrent case, allocated nid can be loaded into free nid cache
and be allocated again.
Thread A Thread B
- f2fs_create
- f2fs_new_inode
- alloc_nid
- __insert_nid_to_list(ALLOC_NID_LIST)
- f2fs_balance_fs_bg
- build_free_nids
- __build_free_nids
- scan_nat_page
- add_free_nid
- __lookup_nat_cache
- f2fs_add_link
- init_inode_metadata
- new_inode_page
- new_node_page
- set_node_addr
- alloc_nid_done
- __remove_nid_from_list(ALLOC_NID_LIST)
- __insert_nid_to_list(FREE_NID_LIST)
This patch makes nat cache lookup and free nid list operation being atomical
to avoid this race condition.
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
[bwh: Backported to 4.9:
- add_free_nid() returns 0 in case of any error (except low memory)
- Tree/list addition has not been moved into __insert_nid_to_list()]
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 file changed