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

[Jianyong Wu]

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...@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