Ocfs2 devel - Oct 2018 - [PATCH 17/25] vfs: enable remap callers that can handle short operations

On Thu, Oct 11, 2018 at 08:15:42AM +0300, Amir Goldstein
wrote:
> On Thu, Oct 11, 2018 at 7:14 AM Darrick J. Wong <darrick.wong at
oracle.com> wrote:
> >
> > From: Darrick J. Wong <darrick.wong at oracle.com>
> >
> > Plumb in a remap flag that enables the filesystem remap handler to
> > shorten remapping requests for callers that can handle it.  Now
> > copy_file_range can report partial success (in case we run up against
> > alignment problems, resource limits, etc.).
> >
> > Signed-off-by: Darrick J. Wong <darrick.wong at oracle.com>
> > Reviewed-by: Amir Goldstein <amir73il at gmail.com>
> > ---
> >  fs/read_write.c    |   15 +++++++++------
> >  include/linux/fs.h |    7 +++++--
> >  mm/filemap.c       |   16 ++++++++++++----
> >  3 files changed, 26 insertions(+), 12 deletions(-)
> >
> >
> > diff --git a/fs/read_write.c b/fs/read_write.c
> > index 6ec908f9a69b..3713893b7e38 100644
> > --- a/fs/read_write.c
> > +++ b/fs/read_write.c
> > @@ -1593,7 +1593,8 @@ ssize_t vfs_copy_file_range(struct file
*file_in, loff_t pos_in,
> >
> >                 cloned =
file_in->f_op->remap_file_range(file_in, pos_in,
> >                                 file_out, pos_out,
> > -                               min_t(loff_t, MAX_RW_COUNT, len), 0);
> > +                               min_t(loff_t, MAX_RW_COUNT, len),
> > +                               RFR_CAN_SHORTEN);
> >                 if (cloned > 0) {
> >                         ret = cloned;
> >                         goto done;
> > @@ -1804,16 +1805,18 @@ int generic_remap_file_range_prep(struct file
*file_in, loff_t pos_in,
> >                  * If the user is attempting to remap a partial EOF
block and
> >                  * it's inside the destination EOF then reject it.
> >                  *
> > -                * We don't support shortening requests, so we can
only reject
> > -                * them.
> > +                * If possible, shorten the request instead of
rejecting it.
> >                  */
> >                 if (is_dedupe)
> >                         ret = -EBADE;
> >                 else if (pos_out + *len < i_size_read(inode_out))
> >                         ret = -EINVAL;
> >
> > -               if (ret)
> > -                       return ret;
> > +               if (ret) {
> > +                       if (!(remap_flags & RFR_CAN_SHORTEN))
> > +                               return ret;
> > +                       *len &= ~blkmask;
> > +               }
> >         }
> >
> >         return 1;
> > @@ -2112,7 +2115,7 @@ int vfs_dedupe_file_range(struct file *file,
struct file_dedupe_range *same)
> >
> >                 deduped = vfs_dedupe_file_range_one(file, off,
dst_file,
> >                                                    
info->dest_offset, len,
> > -                                                   0);
> > +                                                   RFR_CAN_SHORTEN);
> 
> You did not update WARN_ON_ONCE in vfs_dedupe_file_range_one()
> to allow this flag and did not mention dedupe in commit message.
> Was that change intentional in this patch?
> 
> After RFR_SHORT_DEDUPE patch the end result in fine.
Heh, oops, sorry about that.  I'll reissue the patch with the two
corrections.

--D
> Thanks,
> Amir.