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: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index b52c9c0..29dc996 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -1761,40 +1761,67 @@
static bool add_free_nid(struct f2fs_sb_info *sbi, nid_t nid, bool build)
{
struct f2fs_nm_info *nm_i = NM_I(sbi);
- struct free_nid *i;
+ struct free_nid *i, *e;
struct nat_entry *ne;
- int err;
+ int err = -EINVAL;
+ bool ret = false;
/* 0 nid should not be used */
if (unlikely(nid == 0))
return false;
- if (build) {
- /* do not add allocated nids */
- ne = __lookup_nat_cache(nm_i, nid);
- if (ne && (!get_nat_flag(ne, IS_CHECKPOINTED) ||
- nat_get_blkaddr(ne) != NULL_ADDR))
- return false;
- }
-
i = f2fs_kmem_cache_alloc(free_nid_slab, GFP_NOFS);
i->nid = nid;
i->state = NID_NEW;
- if (radix_tree_preload(GFP_NOFS)) {
- kmem_cache_free(free_nid_slab, i);
- return true;
- }
+ if (radix_tree_preload(GFP_NOFS))
+ goto err;
spin_lock(&nm_i->nid_list_lock);
+
+ if (build) {
+ /*
+ * 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)
+ */
+ ne = __lookup_nat_cache(nm_i, nid);
+ if (ne && (!get_nat_flag(ne, IS_CHECKPOINTED) ||
+ nat_get_blkaddr(ne) != NULL_ADDR))
+ goto err_out;
+
+ e = __lookup_free_nid_list(nm_i, nid);
+ if (e) {
+ if (e->state == NID_NEW)
+ ret = true;
+ goto err_out;
+ }
+ }
+ ret = true;
err = __insert_nid_to_list(sbi, i, FREE_NID_LIST, true);
+err_out:
spin_unlock(&nm_i->nid_list_lock);
radix_tree_preload_end();
- if (err) {
+err:
+ if (err)
kmem_cache_free(free_nid_slab, i);
- return true;
- }
- return true;
+ return ret;
}
static void remove_free_nid(struct f2fs_sb_info *sbi, nid_t nid)