fs: Export alloc_empty_backing_file

Hongbo Li · hsiangkao · commit 37364497048c · 2026-01-23T20:01:13.000+08:00
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@huawei.com> Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com> Acked-by: Amir Goldstein <amir73il@gmail.com> Acked-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
diff --git 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

Original file line number	Diff line number	Diff line change
`@@ -308,6 +308,7 @@ struct file alloc_empty_backing_file(int flags, const struct cred cred)`
`308`	`308`	`ff->file.f_mode \|= FMODE_BACKING \| FMODE_NOACCOUNT;`
`309`	`309`	`return &ff->file;`
`310`	`310`	`}`
	`311`	`+EXPORT_SYMBOL_GPL(alloc_empty_backing_file);`
`311`	`312`
`312`	`313`	`/**`
`313`	`314`	`* file_init_path - initialize a 'struct file' based on path`