f2fs: cover more area with nat_tree_lock

BugLink: https://bugs.launchpad.net/bugs/1818797

commit a5131193 upstream.

There was a subtle bug on nat cache management which incurs wrong nid allocation
or wrong block addresses when try_to_free_nats is triggered heavily.
This patch enlarges the previous coverage of nat_tree_lock to avoid data race.
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

fs/f2fs/node.c

@@ -261,13 +261,11 @@ static void cache_nat_entry(struct f2fs_nm_info *nm_i, nid_t nid,
 {
 	struct nat_entry *e;
 
-	down_write(&nm_i->nat_tree_lock);
 	e = __lookup_nat_cache(nm_i, nid);
 	if (!e) {
 		e = grab_nat_entry(nm_i, nid);
 		node_info_from_raw_nat(&e->ni, ne);
 	}
-	up_write(&nm_i->nat_tree_lock);
 }
 
 static void set_node_addr(struct f2fs_sb_info *sbi, struct node_info *ni,
@@ -379,6 +377,8 @@ void get_node_info(struct f2fs_sb_info *sbi, nid_t nid, struct node_info *ni)
 
 	memset(&ne, 0, sizeof(struct f2fs_nat_entry));
 
+	down_write(&nm_i->nat_tree_lock);
+
 	/* Check current segment summary */
 	mutex_lock(&curseg->curseg_mutex);
 	i = lookup_journal_in_cursum(sum, NAT_JOURNAL, nid, 0);
@@ -399,6 +399,7 @@ void get_node_info(struct f2fs_sb_info *sbi, nid_t nid, struct node_info *ni)
 cache:
 	/* cache nat entry */
 	cache_nat_entry(NM_I(sbi), nid, &ne);
+	up_write(&nm_i->nat_tree_lock);
 }
 
 /*
@@ -1440,13 +1441,10 @@ static int add_free_nid(struct f2fs_sb_info *sbi, nid_t nid, bool build)
 
 	if (build) {
 		/* do not add allocated nids */
-		down_read(&nm_i->nat_tree_lock);
 		ne = __lookup_nat_cache(nm_i, nid);
-		if (ne &&
-			(!get_nat_flag(ne, IS_CHECKPOINTED) ||
+		if (ne && (!get_nat_flag(ne, IS_CHECKPOINTED) ||
 				nat_get_blkaddr(ne) != NULL_ADDR))
 			allocated = true;
-		up_read(&nm_i->nat_tree_lock);
 		if (allocated)
 			return 0;
 	}
@@ -1532,6 +1530,8 @@ static void build_free_nids(struct f2fs_sb_info *sbi)
 	ra_meta_pages(sbi, NAT_BLOCK_OFFSET(nid), FREE_NID_PAGES,
 							META_NAT, true);
 
+	down_read(&nm_i->nat_tree_lock);
+
 	while (1) {
 		struct page *page = get_current_nat_page(sbi, nid);
 
@@ -1560,6 +1560,7 @@ static void build_free_nids(struct f2fs_sb_info *sbi)
 			remove_free_nid(nm_i, nid);
 	}
 	mutex_unlock(&curseg->curseg_mutex);
+	up_read(&nm_i->nat_tree_lock);
 
 	ra_meta_pages(sbi, NAT_BLOCK_OFFSET(nm_i->next_scan_nid),
 					nm_i->ra_nid_pages, META_NAT, false);
@@ -1842,14 +1843,12 @@ static void remove_nats_in_journal(struct f2fs_sb_info *sbi)
 
 		raw_ne = nat_in_journal(sum, i);
 
-		down_write(&nm_i->nat_tree_lock);
 		ne = __lookup_nat_cache(nm_i, nid);
 		if (!ne) {
 			ne = grab_nat_entry(nm_i, nid);
 			node_info_from_raw_nat(&ne->ni, &raw_ne);
 		}
 		__set_nat_cache_dirty(nm_i, ne);
-		up_write(&nm_i->nat_tree_lock);
 	}
 	update_nats_in_cursum(sum, -i);
 	mutex_unlock(&curseg->curseg_mutex);
@@ -1883,7 +1882,6 @@ static void __flush_nat_entry_set(struct f2fs_sb_info *sbi,
 	struct f2fs_nat_block *nat_blk;
 	struct nat_entry *ne, *cur;
 	struct page *page = NULL;
-	struct f2fs_nm_info *nm_i = NM_I(sbi);
 
 	/*
 	 * there are two steps to flush nat entries:
@@ -1920,12 +1918,8 @@ static void __flush_nat_entry_set(struct f2fs_sb_info *sbi,
 			raw_ne = &nat_blk->entries[nid - start_nid];
 		}
 		raw_nat_from_node_info(raw_ne, &ne->ni);
-
-		down_write(&NM_I(sbi)->nat_tree_lock);
 		nat_reset_flag(ne);
 		__clear_nat_cache_dirty(NM_I(sbi), ne);
-		up_write(&NM_I(sbi)->nat_tree_lock);
-
 		if (nat_get_blkaddr(ne) == NULL_ADDR)
 			add_free_nid(sbi, nid, false);
 	}
@@ -1937,9 +1931,7 @@ static void __flush_nat_entry_set(struct f2fs_sb_info *sbi,
 
 	f2fs_bug_on(sbi, set->entry_cnt);
 
-	down_write(&nm_i->nat_tree_lock);
 	radix_tree_delete(&NM_I(sbi)->nat_set_root, set->set);
-	up_write(&nm_i->nat_tree_lock);
 	kmem_cache_free(nat_entry_set_slab, set);
 }
 
@@ -1959,6 +1951,9 @@ void flush_nat_entries(struct f2fs_sb_info *sbi)
 
 	if (!nm_i->dirty_nat_cnt)
 		return;
+
+	down_write(&nm_i->nat_tree_lock);
+
 	/*
 	 * if there are no enough space in journal to store dirty nat
 	 * entries, remove all entries from journal and merge them
@@ -1967,7 +1962,6 @@ void flush_nat_entries(struct f2fs_sb_info *sbi)
 	if (!__has_cursum_space(sum, nm_i->dirty_nat_cnt, NAT_JOURNAL))
 		remove_nats_in_journal(sbi);
 
-	down_write(&nm_i->nat_tree_lock);
 	while ((found = __gang_lookup_nat_set(nm_i,
 					set_idx, SETVEC_SIZE, setvec))) {
 		unsigned idx;
@@ -1976,12 +1970,13 @@ void flush_nat_entries(struct f2fs_sb_info *sbi)
 			__adjust_nat_entry_set(setvec[idx], &sets,
 							MAX_NAT_JENTRIES(sum));
 	}
-	up_write(&nm_i->nat_tree_lock);
 
 	/* flush dirty nats in nat entry set */
 	list_for_each_entry_safe(set, tmp, &sets, set_list)
 		__flush_nat_entry_set(sbi, set);
 
+	up_write(&nm_i->nat_tree_lock);
+
 	f2fs_bug_on(sbi, nm_i->dirty_nat_cnt);
 }