On Fri, Oct 5, 2018 at 3:46 AM Darrick J. Wong <darrick.wong@xxxxxxxxxx> wrote:
>
> From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
>
> Change the clone_file_range and dedupe_file_range functions to return
> the number of bytes they operated on. This is the precursor to allowing
> fs implementations to return short clone/dedupe results to the user,
> which will enable us to obey resource limits in a graceful manner.
>
> Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> ---
[...]
> diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
> index aeaefd2a551b..6d792d817538 100644
> --- a/fs/overlayfs/file.c
> +++ b/fs/overlayfs/file.c
> @@ -487,16 +487,21 @@ 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,
> +static s64 ovl_clone_file_range(struct file *file_in, loff_t pos_in,
> struct file *file_out, loff_t pos_out, u64 len)
> {
> - return ovl_copyfile(file_in, pos_in, file_out, pos_out, len, 0,
> - OVL_CLONE);
> + int ret;
> +
> + ret = ovl_copyfile(file_in, pos_in, file_out, pos_out, len, 0,
> + OVL_CLONE);
> + return ret < 0 ? ret : len;
> }
>
> -static int ovl_dedupe_file_range(struct file *file_in, loff_t pos_in,
> +static s64 ovl_dedupe_file_range(struct file *file_in, loff_t pos_in,
> struct file *file_out, loff_t pos_out, u64 len)
> {
> + int ret;
> +
> /*
> * 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).
> @@ -505,8 +510,9 @@ static int ovl_dedupe_file_range(struct file *file_in, loff_t pos_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);
> + ret = ovl_copyfile(file_in, pos_in, file_out, pos_out, len, 0,
> + OVL_DEDUPE);
> + return ret < 0 ? ret : len;
> }
>
This is not pretty at all.
You are blocking the propagation of partial dedupe/clone result
of files that are accessed via overlay over xfs.
Please extend the interface change to the vfs helpers
(i.e. vfs_clone_file_range()) and then the change above is not needed.
Of course you would need to change the 3 callers of
vfs_clone_file_range() that expect 0 is ok.
Please take a look at commit
a725356b6659 ("vfs: swap names of {do,vfs}_clone_file_range()")
That was just merged for rc7.
I do apologize for the churn, but it's a semantic mistake that
I made that needed fixing, so please rebase your work on top
of that and take care not to trip over it.
ioctl_file_clone() and ovl_copy_up_data() just need to interpret
positive return value correctly.
nfsd4_clone_file_range() should have the same return value as
vfs_clone_file_range() to be interpreted in nfsd4_clone(), following
same practice as nfsd4_copy_file_range().
[...]
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 2a4141d36ebf..e5755340e825 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1759,10 +1759,12 @@ struct file_operations {
> #endif
> ssize_t (*copy_file_range)(struct file *, loff_t, struct file *,
> loff_t, size_t, unsigned int);
> - int (*clone_file_range)(struct file *, loff_t, struct file *, loff_t,
> - u64);
> - int (*dedupe_file_range)(struct file *, loff_t, struct file *, loff_t,
> - u64);
> + s64 (*clone_file_range)(struct file *file_in, loff_t pos_in,
> + struct file *file_out, loff_t pos_out,
> + u64 count);
> + s64 (*dedupe_file_range)(struct file *file_in, loff_t pos_in,
> + struct file *file_out, loff_t pos_out,
> + u64 count);
Matthew has objected a similar interface change when it was proposed by Miklos:
https://marc.info/?l=linux-fsdevel&m=152570317110292&w=2
https://marc.info/?l=linux-fsdevel&m=152569298704781&w=2
He claimed that the interface should look like this:
+ loff_t (*dedupe_file_range)(struct file *src, loff_t src_off,
+ struct file *dst, loff_t dst_off, loff_t len);
Thanks,
Amir.
