ext4: use pre-allocated es in __es_insert_extent()

Pass a extent_status pointer prealloc to __es_insert_extent(). If the
pointer is non-null, it is used directly when a new extent_status is
needed to avoid memory allocation failures.
Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20230424033846.4732-5-libaokun1@huawei.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/extents_status.c

@@ -144,7 +144,8 @@
 static struct kmem_cache *ext4_es_cachep;
 static struct kmem_cache *ext4_pending_cachep;
 
-static int __es_insert_extent(struct inode *inode, struct extent_status *newes);
+static int __es_insert_extent(struct inode *inode, struct extent_status *newes,
+			      struct extent_status *prealloc);
 static int __es_remove_extent(struct inode *inode, ext4_lblk_t lblk,
 			      ext4_lblk_t end, int *reserved);
 static int es_reclaim_extents(struct ext4_inode_info *ei, int *nr_to_scan);
@@ -766,7 +767,8 @@ static inline void ext4_es_insert_extent_check(struct inode *inode,
 }
 #endif
 
-static int __es_insert_extent(struct inode *inode, struct extent_status *newes)
+static int __es_insert_extent(struct inode *inode, struct extent_status *newes,
+			      struct extent_status *prealloc)
 {
 	struct ext4_es_tree *tree = &EXT4_I(inode)->i_es_tree;
 	struct rb_node **p = &tree->root.rb_node;
@@ -806,7 +808,10 @@ static int __es_insert_extent(struct inode *inode, struct extent_status *newes)
 		}
 	}
 
-	es = __es_alloc_extent(false);
+	if (prealloc)
+		es = prealloc;
+	else
+		es = __es_alloc_extent(false);
 	if (!es)
 		return -ENOMEM;
 	ext4_es_init_extent(inode, es, newes->es_lblk, newes->es_len,
@@ -866,7 +871,7 @@ int ext4_es_insert_extent(struct inode *inode, ext4_lblk_t lblk,
 	if (err != 0)
 		goto error;
 retry:
-	err = __es_insert_extent(inode, &newes);
+	err = __es_insert_extent(inode, &newes, NULL);
 	if (err == -ENOMEM && __es_shrink(EXT4_SB(inode->i_sb),
 					  128, EXT4_I(inode)))
 		goto retry;
@@ -916,7 +921,7 @@ void ext4_es_cache_extent(struct inode *inode, ext4_lblk_t lblk,
 
 	es = __es_tree_search(&EXT4_I(inode)->i_es_tree.root, lblk);
 	if (!es || es->es_lblk > end)
-		__es_insert_extent(inode, &newes);
+		__es_insert_extent(inode, &newes, NULL);
 	write_unlock(&EXT4_I(inode)->i_es_lock);
 }
 
@@ -1362,7 +1367,7 @@ static int __es_remove_extent(struct inode *inode, ext4_lblk_t lblk,
 					orig_es.es_len - len2;
 			ext4_es_store_pblock_status(&newes, block,
 						    ext4_es_status(&orig_es));
-			err = __es_insert_extent(inode, &newes);
+			err = __es_insert_extent(inode, &newes, NULL);
 			if (err) {
 				es->es_lblk = orig_es.es_lblk;
 				es->es_len = orig_es.es_len;
@@ -2016,7 +2021,7 @@ int ext4_es_insert_delayed_block(struct inode *inode, ext4_lblk_t lblk,
 	if (err != 0)
 		goto error;
 retry:
-	err = __es_insert_extent(inode, &newes);
+	err = __es_insert_extent(inode, &newes, NULL);
 	if (err == -ENOMEM && __es_shrink(EXT4_SB(inode->i_sb),
 					  128, EXT4_I(inode)))
 		goto retry;