Re: [PATCH v1 2/3] NFSD: Implement the COPY call

[Anna Schumaker <Anna.Schumaker@netapp.com>]

On 12/04/2015 10:45 AM, J. Bruce Fields wrote:
> On Thu, Dec 03, 2015 at 03:55:35PM -0500, Anna Schumaker wrote:
>> @@ -498,6 +499,22 @@ __be32 nfsd4_set_nfs4_label(struct svc_rqst *rqstp, struct svc_fh *fhp,
>>  }
>>  #endif
>>  
>> +ssize_t nfsd_copy_range(struct file *src, u64 src_pos,
>> +		       struct file *dst, u64 dst_pos,
>> +		       u64 count)
>> +{
>> +	ssize_t bytes;
>> +	u64 limit = 0x10000000;
> 
> Why that value?  Could I get a comment here?

Whoops!  I had a comment there at one point, but I must have deleted it :(.  That value is to cap copies to 256MB.
> 
>> +
>> +	if (count > limit)
>> +		count = limit;
>> +
>> +	bytes = vfs_copy_file_range(src, src_pos, dst, dst_pos, count, 0);
> 
> Sorry, I lost track of the copy discussions: does this only work on
> filesystems with special support, or does it fall back on doing the copy
> by hand?  Which filesystems (of the exportable filesystems) support
> this?

The system call falls back on doing the copy by hand if there is no filesystem acceleration.

Anna

> 
> --b.
> 
>> +	if (bytes > 0)
>> +		vfs_fsync_range(dst, dst_pos, dst_pos + bytes, 0);
>> +	return bytes;
>> +}
>> +
>>  __be32 nfsd4_vfs_fallocate(struct svc_rqst *rqstp, struct svc_fh *fhp,
>>  			   struct file *file, loff_t offset, loff_t len,
>>  			   int flags)
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