f2fs: give a try to do atomic write in -ENOMEM case

It'd be better to retry writing atomic pages when we get -ENOMEM.
Reviewed-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/segment.c

@@ -309,17 +309,21 @@ static int __commit_inmem_pages(struct inode *inode,
 				inode_dec_dirty_pages(inode);
 				remove_dirty_inode(inode);
 			}
-
+retry:
 			fio.page = page;
 			fio.old_blkaddr = NULL_ADDR;
 			fio.encrypted_page = NULL;
 			fio.need_lock = LOCK_DONE;
 			err = do_write_data_page(&fio);
 			if (err) {
+				if (err == -ENOMEM) {
+					congestion_wait(BLK_RW_ASYNC, HZ/50);
+					cond_resched();
+					goto retry;
+				}
 				unlock_page(page);
 				break;
 			}
-
 			/* record old blkaddr for revoking */
 			cur->old_addr = fio.old_blkaddr;
 			last_idx = page->index;