ext4: using nofail preallocation in ext4_es_insert_delayed_block()

Similar to in ext4_es_remove_extent(), we use a no-fail preallocation
to avoid inconsistencies, except that here we may have to preallocate
two extent_status.

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/20230424033846.4732-8-libaokun1@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

Author: LiBaokun96

fs/ext4/extents_status.c

@@ -2009,7 +2009,10 @@ int ext4_es_insert_delayed_block(struct inode *inode, ext4_lblk_t lblk,
 				 bool allocated)
 {
 	struct extent_status newes;
-	int err = 0;
+	int err1 = 0;
+	int err2 = 0;
+	struct extent_status *es1 = NULL;
+	struct extent_status *es2 = NULL;
 
 	if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY)
 		return 0;
@@ -2024,29 +2027,37 @@ int ext4_es_insert_delayed_block(struct inode *inode, ext4_lblk_t lblk,
 
 	ext4_es_insert_extent_check(inode, &newes);
 
+retry:
+	if (err1 && !es1)
+		es1 = __es_alloc_extent(true);
+	if ((err1 || err2) && !es2)
+		es2 = __es_alloc_extent(true);
 	write_lock(&EXT4_I(inode)->i_es_lock);
 
-	err = __es_remove_extent(inode, lblk, lblk, NULL, NULL);
-	if (err != 0)
+	err1 = __es_remove_extent(inode, lblk, lblk, NULL, es1);
+	if (err1 != 0)
 		goto error;
-retry:
-	err = __es_insert_extent(inode, &newes, NULL);
-	if (err == -ENOMEM && __es_shrink(EXT4_SB(inode->i_sb),
-					  128, EXT4_I(inode)))
-		goto retry;
-	if (err != 0)
+
+	err2 = __es_insert_extent(inode, &newes, es2);
+	if (err2 != 0)
 		goto error;
 
 	if (allocated)
 		__insert_pending(inode, lblk);
 
+	/* es is pre-allocated but not used, free it. */
+	if (es1 && !es1->es_len)
+		__es_free_extent(es1);
+	if (es2 && !es2->es_len)
+		__es_free_extent(es2);
 error:
 	write_unlock(&EXT4_I(inode)->i_es_lock);
+	if (err1 || err2)
+		goto retry;
 
 	ext4_es_print_tree(inode);
 	ext4_print_pending_tree(inode);
-
-	return err;
+	return 0;
 }
 
 /*