Re: [PATCH 08/25] vfs: combine the clone and dedupe into a single remap_file_range

Darrick J. Wong
2018-10-10T15:13:21Z

On Wed, Oct 10, 2018 at 08:54:44AM +0300, Amir Goldstein wrote:
> On Wed, Oct 10, 2018 at 3:12 AM Darrick J. Wong <darrick.wong@oracle.com> wrote:
> >
> > From: Darrick J. Wong <darrick.wong@oracle.com>
> >
> > Combine the clone_file_range and dedupe_file_range operations into a
> > single remap_file_range file operation dispatch since they're
> > fundamentally the same operation. The differences between the two can
> > be made in the prep functions.
> >
> > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> > ---
>
> I like this. Nits below.
>
> [...]
>
> > diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> > index d60b6caf09e8..e22b294fa25b 100644
> > --- a/fs/btrfs/ioctl.c
> > +++ b/fs/btrfs/ioctl.c
> > @@ -3627,26 +3627,6 @@ static int btrfs_extent_same(struct inode *src, u64 loff, u64 olen,
> > return ret;
> > }
> >
> > -int btrfs_dedupe_file_range(struct file *src_file, loff_t src_loff,
> > - struct file *dst_file, loff_t dst_loff,
> > - u64 olen)
> > -{
> > - struct inode *src = file_inode(src_file);
> > - struct inode *dst = file_inode(dst_file);
> > - u64 bs = BTRFS_I(src)->root->fs_info->sb->s_blocksize;
> > -
> > - if (WARN_ON_ONCE(bs < PAGE_SIZE)) {
> > - /*
> > - * Btrfs does not support blocksize < page_size. As a
> > - * result, btrfs_cmp_data() won't correctly handle
> > - * this situation without an update.
> > - */
> > - return -EINVAL;
> > - }
> > -
> > - return btrfs_extent_same(src, src_loff, olen, dst, dst_loff);
> > -}
> > -
> > static int clone_finish_inode_update(struct btrfs_trans_handle *trans,
> > struct inode *inode,
> > u64 endoff,
> > @@ -4348,9 +4328,27 @@ static noinline int btrfs_clone_files(struct file *file, struct file *file_src,
> > return ret;
> > }
> >
> > -int btrfs_clone_file_range(struct file *src_file, loff_t off,
> > - struct file *dst_file, loff_t destoff, u64 len)
> > +int btrfs_remap_file_range(struct file *src_file, loff_t off,
> > + struct file *dst_file, loff_t destoff, u64 len,
> > + unsigned int flags)
> > {
> > + if (flags & RFR_IDENTICAL_DATA) {
> > + struct inode *src = file_inode(src_file);
> > + struct inode *dst = file_inode(dst_file);
> > + u64 bs = BTRFS_I(src)->root->fs_info->sb->s_blocksize;
> > +
> > + if (WARN_ON_ONCE(bs < PAGE_SIZE)) {
> > + /*
> > + * Btrfs does not support blocksize < page_size. As a
> > + * result, btrfs_cmp_data() won't correctly handle
> > + * this situation without an update.
> > + */
> > + return -EINVAL;
> > + }
> > +
> > + return btrfs_extent_same(src, off, len, dst, destoff);
> > + }
> > +
>
> Seems weird that you would do that instead of:
>
> + if (flags & ~RFR_IDENTICAL_DATA)
> + return -EINVAL;
> + if (flags & RFR_IDENTICAL_DATA)
> + return btrfs_dedupe_file_range(src, off, dst, destoff, len);

Hmm. The flags validation thing is kind of a mess here. There should be a:

#define RFR_VALID_FLAGS (RFR_IDENTICAL_DATA | /* add other RFR flags */)

And all these functions should also gate on:

if (remap_flags & ~RFR_VALID_FLAGS) {
WARN_ON(...);
return -EINVAL;
}

Though FWIW the btrfs implementation actually will support all three
flags, so the particular structure of these checks here are correct if
you add in my self-criticism above.

>
> > return btrfs_clone_files(dst_file, src_file, off, len, destoff);
> > }
> >
> > diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
> > index 7065426b3280..bf971fd7cab2 100644
> > --- a/fs/cifs/cifsfs.c
> > +++ b/fs/cifs/cifsfs.c
> > @@ -975,8 +975,9 @@ const struct inode_operations cifs_symlink_inode_ops = {
> > .listxattr = cifs_listxattr,
> > };
> >
> > -static int cifs_clone_file_range(struct file *src_file, loff_t off,
> > - struct file *dst_file, loff_t destoff, u64 len)
> > +static int cifs_remap_file_range(struct file *src_file, loff_t off,
> > + struct file *dst_file, loff_t destoff, u64 len,
> > + unsigned int flags)
> > {
> > struct inode *src_inode = file_inode(src_file);
> > struct inode *target_inode = file_inode(dst_file);
> > @@ -986,6 +987,9 @@ static int cifs_clone_file_range(struct file *src_file, loff_t off,
> > unsigned int xid;
> > int rc;
> >
> > + if (flags & RFR_IDENTICAL_DATA)
> > + return -EOPNOTSUPP;
> > +
>
> I think everyone would be better off with:
> + if (flags)
> + return -EINVAL;
>
> This way you won't need to change all filesystem implementations
> every time that you add a new RFR flag.
> Lucky for us, dedup already return -EINVAL if (!f_op->dedupe_file_range)
> (and not -EOPNOTSUPP).

Ugh, right, I forgot about that, um, quirk of the interface. :(

> [...]
> > diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
> > index 986313da0c88..693bd0620a81 100644
> > --- a/fs/overlayfs/file.c
> > +++ b/fs/overlayfs/file.c
> > @@ -489,26 +489,28 @@ static ssize_t ovl_copy_file_range(struct file *file_in, loff_t pos_in,
> > OVL_COPY);
> > }
> >
> > -static int ovl_clone_file_range(struct file *file_in, loff_t pos_in,
> > - struct file *file_out, loff_t pos_out, u64 len)
> > +static int ovl_remap_file_range(struct file *file_in, loff_t pos_in,
> > + struct file *file_out, loff_t pos_out,
> > + u64 len, unsigned int flags)
> > {
> > - return ovl_copyfile(file_in, pos_in, file_out, pos_out, len, 0,
> > - OVL_CLONE);
> > -}
> > + enum ovl_copyop op;
> > +
> > + if (flags & RFR_IDENTICAL_DATA)
> > + op = OVL_DEDUPE;
> > + else
> > + op = OVL_CLONE;
> >
> > -static int ovl_dedupe_file_range(struct file *file_in, loff_t pos_in,
> > - struct file *file_out, loff_t pos_out, u64 len)
> > -{
> > /*
> > * Don't copy up because of a dedupe request, this wouldn't make sense
> > * most of the time (data would be duplicated instead of deduplicated).
> > */
> > - if (!ovl_inode_upper(file_inode(file_in)) ||
> > - !ovl_inode_upper(file_inode(file_out)))
> > + if (op == OVL_DEDUPE &&
> > + (!ovl_inode_upper(file_inode(file_in)) ||
> > + !ovl_inode_upper(file_inode(file_out))))
> > return -EPERM;
> >
> > return ovl_copyfile(file_in, pos_in, file_out, pos_out, len, 0,
> > - OVL_DEDUPE);
> > + op);
> > }
> >
>
> Apart from the generic check invalid flags comment - ACK on ovl part.

Thanks for the review! Is that an official Acked-by to add to the
commit message, or an informal ACK?

--D

> Thanks,
> Amir.