linux-kernel - [PATCH v9 03/10] fs: Export alloc_empty_backing

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Message-ID: <20251117132537.227116-4-lihongbo22@huawei.com>
Date: Mon, 17 Nov 2025 13:25:30 +0000
From: Hongbo Li <lihongbo22@...wei.com>
To: <hsiangkao@...ux.alibaba.com>, <chao@...nel.org>, <brauner@...nel.org>,
	<djwong@...nel.org>, <amir73il@...il.com>, <joannelkoong@...il.com>
CC: <lihongbo22@...wei.com>, <linux-fsdevel@...r.kernel.org>,
	<linux-erofs@...ts.ozlabs.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH v9 03/10] fs: Export alloc_empty_backing_file

There is no need to open nonexistent real files if backing files
couldn't be backed by real files (e.g., EROFS page cache sharing
doesn't need typical real files to open again).

Therefore, we export the alloc_empty_backing_file() helper, allowing
filesystems to dynamically set the backing file without real file
open. This is particularly useful for obtaining the correct @path
and @inode when calling file_user_path() and file_user_inode().

Signed-off-by: Hongbo Li <lihongbo22@...wei.com>
---
 fs/file_table.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/file_table.c b/fs/file_table.c
index b223d873e48b..7508f69a1839 100644
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -308,6 +308,7 @@ struct file *alloc_empty_backing_file(int flags, const struct cred *cred)
 	ff->file.f_mode |= FMODE_BACKING | FMODE_NOACCOUNT;
 	return &ff->file;
 }
+EXPORT_SYMBOL_GPL(alloc_empty_backing_file);

 /**
  * file_init_path - initialize a 'struct file' based on path
-- 
2.22.0