On 05/24/2011 07:21 PM, Trond Myklebust wrote:
> On Tue, 2011-05-24 at 18:56 +0300, Boaz Harrosh wrote:
>> In the nfs_pageio_descriptor passed to pg_test() together with the two pages:
>> Which member means the current byte_size (or page_count?) and what is the
>> meaning of some of these fields
>>
>> struct nfs_pageio_descriptor {
>> ....
>> unsigned long pg_bytes_written;
>> Is this for result after read/write?
>
> This is the total number of bytes we successfully called
> nfs_pageio_doio() for. In other words, it should represent the total
> number of bytes we put on the wire.
>
>> size_t pg_count;
>> Is this the number of pages added up to now?
>> Do we also have the start of the first page?
>
> This is the number of bytes we have successfully coalesced into the
> current i/o.
>
>> size_t pg_bsize;
>> So I understand this is the max allowed pages. Does
>> that mean also the allocated size or Just the negotiated
>> size with the server? (Really bad name if you ask me)
>
> It means the 'block size'. In ordinary NFS parlance that will be the
> 'rsize' or the 'wsize'.
>
>> unsigned int pg_base;
>> Is that the index of the first page? That cannot be, the page->index
>> needs to be 64bit. So what is this then?
>
> It is used when dealing with I/O requests that are not page aligned.
>
> If you consider the pages that we are to write out in the current I/O as
> a single buffer, then the pg_base is the offset of the first byte to
> write out/read in.
>
Thanks Trond, I think I understand and can write the proper implementation
for objects->pg_test now. One more question. I need the file offset
of the beginning of the write would that then be:
int objlayout_pg_test(struct nfs_pageio_descriptor *pgio, struct nfs_page *prev,
struct nfs_page *req)
}
struct nfs_page *first_pg = list_entry(pgio->pg_list.next, struct nfs_page, wb_list);
u64 io_offset = (first_pg->wb_index << PAGE_SHIFT) + first_pg->wb_offset;
...
}
Thanks
Boaz
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