On 2/2/2016 02:38, J. Bruce Fields wrote:
> On Sun, Jan 31, 2016 at 08:50:10PM +0800, Kinglong Mee wrote:
>> ltp fsync02 will cause nfs sending LAYOUTCOMMIT with length
>> larger than two pages. nfsd returns NFSERR_BAD_XDR right now.
>
> This is with the xfs block layout?
Yes, xfs block layout.
Tested by ltp's fsync02.
thanks,
Kinglong Mee
>
> Christoph, do we know anything about average or worst-case sizes for
> that layout update field?
>
>> This patch lets nfsd supports read buffer from multiples pages.
>
> Hm. We'll end up kmalloc()ing the passed-in field length:
>
> p = argp->tmpp = kmalloc(nbytes, GFP_KERNEL);
>
> We still do still have that (avail + argp->pagelen) limit, so we're not
> going to pass arbitrarily large nbytes straight from the network to
> kmalloc. But we do try to avoid depending on higher-order allocations.
>
> --b.
>
>>
>> Signed-off-by: Kinglong Mee <kinglongmee@xxxxxxxxx>
>> ---
>> fs/nfsd/nfs4xdr.c | 18 ++++++++++++++----
>> 1 file changed, 14 insertions(+), 4 deletions(-)
>>
>> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
>> index d6ef095..fcf399f 100644
>> --- a/fs/nfsd/nfs4xdr.c
>> +++ b/fs/nfsd/nfs4xdr.c
>> @@ -143,11 +143,11 @@ static __be32 *read_buf(struct nfsd4_compoundargs *argp, u32 nbytes)
>> * Maybe we need a new page, maybe we have just run out
>> */
>> unsigned int avail = (char *)argp->end - (char *)argp->p;
>> + unsigned int copied = 0;
>> __be32 *p;
>> +
>> if (avail + argp->pagelen < nbytes)
>> return NULL;
>> - if (avail + PAGE_SIZE < nbytes) /* need more than a page !! */
>> - return NULL;
>> /* ok, we can do it with the current plus the next page */
>> if (nbytes <= sizeof(argp->tmp))
>> p = argp->tmp;
>> @@ -164,9 +164,19 @@ static __be32 *read_buf(struct nfsd4_compoundargs *argp, u32 nbytes)
>> * guarantee p points to at least nbytes bytes.
>> */
>> memcpy(p, argp->p, avail);
>> + copied += avail;
>> + nbytes -= avail;
>> +
>> + while (nbytes > PAGE_SIZE) {
>> + next_decode_page(argp);
>> + memcpy(((char*)p) + copied, argp->p, PAGE_SIZE);
>> + copied += PAGE_SIZE;
>> + nbytes -= PAGE_SIZE;
>> + }
>> +
>> next_decode_page(argp);
>> - memcpy(((char*)p)+avail, argp->p, (nbytes - avail));
>> - argp->p += XDR_QUADLEN(nbytes - avail);
>> + memcpy(((char*)p) + copied, argp->p, nbytes);
>> + argp->p += XDR_QUADLEN(nbytes);
>> return p;
>> }
>>
>> --
>> 2.5.0
>
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