On Wed, May 29, 2019 at 10:08:44PM +0300, Amir Goldstein wrote:
> On Wed, May 29, 2019 at 9:27 PM Darrick J. Wong <darrick.wong@xxxxxxxxxx> wrote:
> >
> > 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.
>
> Nope that's a typo. Good spotting.
> Overlayfs doesn't set FMODE_NOCMTIME (yet). Only xfs does from
> XFS_IOC_OPEN_BY_HANDLE, but I think Dave said that is a deprecated
> API. so should have been very_unlikely().
It is most definitely not a deprecated API. I don't know where you
got that idea from. It's used explicitly by the xfs utilities to
perform invisible IO. Anyone who runs xfs_fsr or xfsdump or has an
application that links to libhandle is using XFS_IOC_OPEN_BY_HANDLE
and FMODE_NOCMTIME....
-Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
