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?
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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