[PATCH v4 6/9] vfs: introduce file_modified() helper

Amir Goldstein
2019-05-31T16:47:23Z

The combination of file_remove_privs() and file_update_mtime() is
quite common in filesystem ->write_iter() methods.

Modelled after the helper file_accessed(), introduce file_modified()
and use it from generic_remap_file_range_prep().

Note that the order of calling file_remove_privs() before
file_update_mtime() in the helper was matched to the more common order by
filesystems and not the current order in generic_remap_file_range_prep().

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
fs/inode.c | 20 ++++++++++++++++++++
fs/read_write.c | 21 +++------------------
include/linux/fs.h | 2 ++
3 files changed, 25 insertions(+), 18 deletions(-)

diff --git a/fs/inode.c b/fs/inode.c
index df6542ec3b88..4348cfb14562 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1899,6 +1899,26 @@ int file_update_time(struct file *file)
}
EXPORT_SYMBOL(file_update_time);

+/* Caller must hold the file's inode lock */
+int file_modified(struct file *file)
+{
+ int err;
+
+ /*
+ * Clear the security bits if the process is not being run by root.
+ * This keeps people from modifying setuid and setgid binaries.
+ */
+ err = file_remove_privs(file);
+ if (err)
+ return err;
+
+ if (unlikely(file->f_mode & FMODE_NOCMTIME))
+ return 0;
+
+ return file_update_time(file);
+}
+EXPORT_SYMBOL(file_modified);
+
int inode_needs_sync(struct inode *inode)
{
if (IS_SYNC(inode))
diff --git a/fs/read_write.c b/fs/read_write.c
index b0fb1176b628..cec7e7b1f693 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -1980,25 +1980,10 @@ int generic_remap_file_range_prep(struct file *file_in, loff_t pos_in,
return ret;

/* If can't alter the file contents, we're done. */
- if (!(remap_flags & REMAP_FILE_DEDUP)) {
- /* Update the timestamps, since we can alter file contents. */
- if (!(file_out->f_mode & FMODE_NOCMTIME)) {
- ret = file_update_time(file_out);
- if (ret)
- return ret;
- }
+ if (!(remap_flags & REMAP_FILE_DEDUP))
+ ret = file_modified(file_out);

- /*
- * Clear the security bits if the process is not being run by
- * root. This keeps people from modifying setuid and setgid
- * binaries.
- */
- ret = file_remove_privs(file_out);
- if (ret)
- return ret;
- }
-
- return 0;
+ return ret;
}
EXPORT_SYMBOL(generic_remap_file_range_prep);

diff --git a/include/linux/fs.h b/include/linux/fs.h
index e4d382c4342a..79ffa2958bd8 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2177,6 +2177,8 @@ static inline void file_accessed(struct file *file)
touch_atime(&file->f_path);
}

+extern int file_modified(struct file *file);
+
int sync_inode(struct inode *inode, struct writeback_control *wbc);
int sync_inode_metadata(struct inode *inode, int wait);

--
2.17.1