On Wed, May 29, 2019 at 08:43:10PM +0300, Amir Goldstein wrote:
> 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@xxxxxxxxx>
> ---
> 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..2885f2f2c7a5 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 (likely(file->f_mode & FMODE_NOCMTIME))
I would not have thought NOCMTIME is likely?
Maybe it is for io requests coming from overlayfs, but for regular uses
I don't think that's true.
--D
> + 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
>
