f2fs: fix race condition in between free nid allocator/initializer
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: NJaegeuk Kim <jaegeuk@kernel.org> Signed-off-by: NChao Yu <yuchao0@huawei.com> Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>
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