[RFC PATCH 1/2] vfs: pass file down when getattr to avoid losing info.

[Jianyong Wu <jianyong.wu@arm.com>]

Currently, getting attribute for a file represented by fd is always
by inode or path which may lead to bug for a certain network file system.
Adding file struct into struct kstat and assigning file for it in
vfs_statx_fd can avoid this issue. This change refers to struct istat.

Signed-off-by: Jianyong Wu <jianyong.wu@arm.com>
---
 fs/stat.c            | 1 +
 include/linux/stat.h | 6 ++++++
 2 files changed, 7 insertions(+)

diff --git a/fs/stat.c b/fs/stat.c
index 44f8ad346db4..0dee5487f6d6 100644
--- a/fs/stat.c
+++ b/fs/stat.c
@@ -147,6 +147,7 @@ int vfs_statx_fd(unsigned int fd, struct kstat *stat,
 		return -EINVAL;
 
 	f = fdget_raw(fd);
+	stat->filp = f.file;
 	if (f.file) {
 		error = vfs_getattr(&f.file->f_path, stat,
 				    request_mask, query_flags);
diff --git a/include/linux/stat.h b/include/linux/stat.h
index 56614af83d4a..4755c528d49a 100644
--- a/include/linux/stat.h
+++ b/include/linux/stat.h
@@ -48,6 +48,12 @@ struct kstat {
 	struct timespec64 btime;			/* File creation time */
 	u64		blocks;
 	u64		mnt_id;
+
+	/*
+	 * Not an attribute, but an auxiliary info for filesystems wanting to
+	 * implement an fstat() like method.
+	 */
+	struct file	*filp;
 };
 
 #endif
-- 
2.17.1