Commit 8154ef27 authored by Chuck Lever's avatar Chuck Lever Committed by J. Bruce Fields
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NFSD: Clean up legacy NFS WRITE argument XDR decoders 



Move common code in NFSD's legacy NFS WRITE decoders into a helper.
The immediate benefit is reduction of code duplication and some nice
micro-optimizations (see below).

In the long term, this helper can perform a per-transport call-out
to fill the rq_vec (say, using RDMA Reads).

The legacy WRITE decoders and procs are changed to work like NFSv4,
which constructs the rq_vec just before it is about to call
vfs_writev.

Why? Calling a transport call-out from the proc instead of the XDR
decoder means that the incoming FH can be resolved to a particular
filesystem and file. This would allow pages from the backing file to
be presented to the transport to be filled, rather than presenting
anonymous pages and copying or flipping them into the file's page
cache later.

I also prefer using the pages in rq_arg.pages, instead of pulling
the data pages directly out of the rqstp::rq_pages array. This is
currently the way the NFSv3 write decoder works, but the other two
do not seem to take this approach. Fixing this removes the only
reference to rq_pages found in NFSD, eliminating an NFSD assumption
about how transports use the pages in rq_pages.

Lastly, avoid setting up the first element of rq_vec as a zero-
length buffer. This happens with an RDMA transport when a normal
Read chunk is present because the data payload is in rq_arg's
page list (none of it is in the head buffer).

Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
Signed-off-by: default avatarJ. Bruce Fields <bfields@redhat.com>
parent fff4080b

fs/nfsd/nfs3proc.c

+6 −2
Original line number Diff line number Diff line
@@ -192,6 +192,7 @@ nfsd3_proc_write(struct svc_rqst *rqstp) 
	struct nfsd3_writeres *resp = rqstp->rq_resp;

	__be32	nfserr;

	unsigned long cnt = argp->len;

	unsigned int nvecs;



	dprintk("nfsd: WRITE(3)    %s %d bytes at %Lu%s\n",

				SVCFH_fmt(&argp->fh),
@@ -201,9 +202,12 @@ nfsd3_proc_write(struct svc_rqst *rqstp) 


	fh_copy(&resp->fh, &argp->fh);

	resp->committed = argp->stable;

	nvecs = svc_fill_write_vector(rqstp, &argp->first, cnt);

	if (!nvecs)

		RETURN_STATUS(nfserr_io);

	nfserr = nfsd_write(rqstp, &resp->fh, argp->offset,

				rqstp->rq_vec, argp->vlen,

				&cnt, resp->committed);

			    rqstp->rq_vec, nvecs, &cnt,

			    resp->committed);

	resp->count = cnt;

	RETURN_STATUS(nfserr);

}

fs/nfsd/nfs3xdr.c

+4 −12
Original line number Diff line number Diff line
@@ -391,7 +391,7 @@ int 
nfs3svc_decode_writeargs(struct svc_rqst *rqstp, __be32 *p)

{

	struct nfsd3_writeargs *args = rqstp->rq_argp;

	unsigned int len, v, hdr, dlen;

	unsigned int len, hdr, dlen;

	u32 max_blocksize = svc_max_payload(rqstp);

	struct kvec *head = rqstp->rq_arg.head;

	struct kvec *tail = rqstp->rq_arg.tail;
@@ -433,17 +433,9 @@ nfs3svc_decode_writeargs(struct svc_rqst *rqstp, __be32 *p) 
		args->count = max_blocksize;

		len = args->len = max_blocksize;

	}

	rqstp->rq_vec[0].iov_base = (void*)p;

	rqstp->rq_vec[0].iov_len = head->iov_len - hdr;

	v = 0;

	while (len > rqstp->rq_vec[v].iov_len) {

		len -= rqstp->rq_vec[v].iov_len;

		v++;

		rqstp->rq_vec[v].iov_base = page_address(rqstp->rq_pages[v]);

		rqstp->rq_vec[v].iov_len = PAGE_SIZE;

	}

	rqstp->rq_vec[v].iov_len = len;

	args->vlen = v + 1;



	args->first.iov_base = (void *)p;

	args->first.iov_len = head->iov_len - hdr;

	return 1;

}

fs/nfsd/nfsproc.c

+7 −2
Original line number Diff line number Diff line
@@ -212,13 +212,18 @@ nfsd_proc_write(struct svc_rqst *rqstp) 
	struct nfsd_attrstat *resp = rqstp->rq_resp;

	__be32	nfserr;

	unsigned long cnt = argp->len;

	unsigned int nvecs;



	dprintk("nfsd: WRITE    %s %d bytes at %d\n",

		SVCFH_fmt(&argp->fh),

		argp->len, argp->offset);



	nfserr = nfsd_write(rqstp, fh_copy(&resp->fh, &argp->fh), argp->offset,

				rqstp->rq_vec, argp->vlen, &cnt, NFS_DATA_SYNC);

	nvecs = svc_fill_write_vector(rqstp, &argp->first, cnt);

	if (!nvecs)

		return nfserr_io;

	nfserr = nfsd_write(rqstp, fh_copy(&resp->fh, &argp->fh),

			    argp->offset, rqstp->rq_vec, nvecs,

			    &cnt, NFS_DATA_SYNC);

	return nfsd_return_attrs(nfserr, resp);

}

fs/nfsd/nfsxdr.c

+2 −12
Original line number Diff line number Diff line
@@ -287,7 +287,6 @@ nfssvc_decode_writeargs(struct svc_rqst *rqstp, __be32 *p) 
	struct nfsd_writeargs *args = rqstp->rq_argp;

	unsigned int len, hdr, dlen;

	struct kvec *head = rqstp->rq_arg.head;

	int v;



	p = decode_fh(p, &args->fh);

	if (!p)
@@ -323,17 +322,8 @@ nfssvc_decode_writeargs(struct svc_rqst *rqstp, __be32 *p) 
	if (dlen < XDR_QUADLEN(len)*4)

		return 0;



	rqstp->rq_vec[0].iov_base = (void*)p;

	rqstp->rq_vec[0].iov_len = head->iov_len - hdr;

	v = 0;

	while (len > rqstp->rq_vec[v].iov_len) {

		len -= rqstp->rq_vec[v].iov_len;

		v++;

		rqstp->rq_vec[v].iov_base = page_address(rqstp->rq_pages[v]);

		rqstp->rq_vec[v].iov_len = PAGE_SIZE;

	}

	rqstp->rq_vec[v].iov_len = len;

	args->vlen = v + 1;

	args->first.iov_base = (void *)p;

	args->first.iov_len = head->iov_len - hdr;

	return 1;

}

fs/nfsd/xdr.h

+1 −1
Original line number Diff line number Diff line
@@ -34,7 +34,7 @@ struct nfsd_writeargs { 
	svc_fh			fh;

	__u32			offset;

	int			len;

	int			vlen;

	struct kvec		first;

};



struct nfsd_createargs {

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