On Tue, Jan 23, 2018 at 02:30:57PM -0800, Chuck Lever wrote:
>
>
> > On Jan 23, 2018, at 12:52 PM, Bruce Fields <bfields@xxxxxxxxxxxx> wrote:
> >
> > On Mon, Jan 22, 2018 at 05:09:35PM -0800, Chuck Lever wrote:
> >>
> >>
> >>> On Jan 22, 2018, at 2:00 PM, J. Bruce Fields <bfields@xxxxxxxxxxxx> wrote:
> >>>
> >>> On Wed, Jan 03, 2018 at 03:42:35PM -0500, Chuck Lever wrote:
> >>>> Move common code in NFSD's symlink arg decoders into a helper. The
> >>>> immediate benefits include:
> >>>>
> >>>> - one fewer data copies on transports that support DDP
> >>>> - no memory allocation in the NFSv4 XDR decoder
> >>>> - consistent error checking across all versions
> >>>> - reduction of code duplication
> >>>> - support for both legal forms of SYMLINK requests on RDMA
> >>>> transports for all versions of NFS (in particular, NFSv2, for
> >>>> completeness)
> >>>>
> >>>> In the long term, this helper is an appropriate spot to perform a
> >>>> per-transport call-out to fill the pathname argument using, say,
> >>>> RDMA Reads.
> >>>>
> >>>> Filling the pathname in the proc function also means that eventually
> >>>> the incoming filehandle can be interpreted so that filesystem-
> >>>> specific memory can be allocated as a sink for the pathname
> >>>> argument, rather than using anonymous pages.
> >>>>
> >>>> Wondering why the current code punts a zero-length SYMLINK. Is it
> >>>> illegal to create a zero-length SYMLINK on Linux?
> >>>
> >>> SYMLINK(2) says
> >>>
> >>> ENOENT A directory component in linkpath does not exist or is a
> >>> dangling symbolic link, or target or linkpath is an empty
> >>> string.
> >>>
> >>> That doesn't explain the INVAL, or why this is the right place to be
> >>> checking it.
> >>
> >> RFC 1813:
> >>
> >> NFS3ERR_IO
> >> NFS3ERR_ACCES
> >> NFS3ERR_EXIST
> >> NFS3ERR_NOTDIR
> >> NFS3ERR_NOSPC
> >> NFS3ERR_ROFS
> >> NFS3ERR_NAMETOOLONG
> >> NFS3ERR_DQUOT
> >> NFS3ERR_STALE
> >> NFS3ERR_BADHANDLE
> >> NFS3ERR_NOTSUPP
> >> NFS3ERR_SERVERFAULT
> >>
> >> Interestingly, neither INVAL nor NOENT are valid
> >> status codes for NFSv3 SYMLINK. NFS3ERR_NOTSUPP
> >> might be closest, I suppose.
> >>
> >> RFC 5661 says explicitly:
> >>
> >> If the objname has a length of zero, or if objname does not obey the
> >> UTF-8 definition, the error NFS4ERR_INVAL will be returned.
> >>
> >> And lists these as valid status codes for CREATE(NF4LNK):
> >>
> >> | NFS4ERR_ACCESS, NFS4ERR_ATTRNOTSUPP, |
> >> | NFS4ERR_BADCHAR, NFS4ERR_BADNAME, |
> >> | NFS4ERR_BADOWNER, NFS4ERR_BADTYPE, |
> >> | NFS4ERR_BADXDR, NFS4ERR_DEADSESSION, |
> >> | NFS4ERR_DELAY, NFS4ERR_DQUOT, |
> >> | NFS4ERR_EXIST, NFS4ERR_FHEXPIRED, |
> >> | NFS4ERR_INVAL, NFS4ERR_IO, NFS4ERR_MLINK, |
> >> | NFS4ERR_MOVED, NFS4ERR_NAMETOOLONG, |
> >> | NFS4ERR_NOFILEHANDLE, NFS4ERR_NOSPC, |
> >> | NFS4ERR_NOTDIR, NFS4ERR_OP_NOT_IN_SESSION, |
> >> | NFS4ERR_PERM, NFS4ERR_REP_TOO_BIG, |
> >> | NFS4ERR_REP_TOO_BIG_TO_CACHE, |
> >> | NFS4ERR_REQ_TOO_BIG, |
> >> | NFS4ERR_RETRY_UNCACHED_REP, NFS4ERR_ROFS, |
> >> | NFS4ERR_SERVERFAULT, NFS4ERR_STALE, |
> >> | NFS4ERR_TOO_MANY_OPS, |
> >> | NFS4ERR_UNSAFE_COMPOUND |
> >>
> >>
> >>> I'm a little nervous about the NULL termination in
> >>> svc_fill_symlink_pathname; how do we know it's safe to write a zero
> >>> there? I haven't checked it carefully yet.
> >>
> >> svc_fill_symlink_pathname grabs a whole fresh page
> >> from @rqstp. It is safe to write bytes anywhere in
> >> that page.
> >
> > How do we know it's safe to grab another page?
>
> It's safe in the v3 case because that's what the v3
> decoder currently does. I think you are concerned
> about the NFSv4 COMPOUND case on TCP, for arbitrarily
> large compounds? Given that we have 257-ish pages
> in the rqstp->rq_pages array (ie, that number is
> bounded) I'm not sure how we can ever be sure there
> are enough pages for all combinations of NFS
> operations.
Right, I think it just depends on some maximum lengths being checked
earlier. So my worry is that this my violate some assumptions about how
many pages we need to handle a request of a certain length.
I'll go remind myself how this works. We need some documentation here
at least. So I may end up postponing these after all....
> > (Could we run out of
> > pages? I'd probably know the answer if I'd rewritten this code
> > recently, but I haven't and the details are swapped out....)
> >
> > Also I don't think that's true in the first->iov_base == 0 case.
>
> This case occurs when an RDMA transport has filled
> in the first page of arg->pages with the symlink
> contents. It's also a whole fresh page that was
> obtained from rqstp->rq_pages.
OK, I wasn't following that case.
--b.
>
> Here, are you concerned about the client sending a
> COMPOUND over RPC/RDMA that has more than one SYMLINK
> operation? Our server currently supports only one Read
> chunk per RPC.
>
>
> > --b.
> >
> >>
> >>
> >>> --g.
> >>>
> >>>>
> >>>> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> >>>> ---
> >>>> fs/nfsd/nfs3proc.c | 10 +++++++
> >>>> fs/nfsd/nfs3xdr.c | 51 ++++++++-------------------------
> >>>> fs/nfsd/nfs4proc.c | 7 +++++
> >>>> fs/nfsd/nfs4xdr.c | 10 +++++--
> >>>> fs/nfsd/nfsproc.c | 14 +++++----
> >>>> fs/nfsd/nfsxdr.c | 49 +++++++++++++++++++-------------
> >>>> fs/nfsd/xdr.h | 1 +
> >>>> fs/nfsd/xdr3.h | 1 +
> >>>> fs/nfsd/xdr4.h | 2 +
> >>>> include/linux/sunrpc/svc.h | 2 +
> >>>> net/sunrpc/svc.c | 67 ++++++++++++++++++++++++++++++++++++++++++++
> >>>> 11 files changed, 146 insertions(+), 68 deletions(-)
> >>>>
> >>>> diff --git a/fs/nfsd/nfs3proc.c b/fs/nfsd/nfs3proc.c
> >>>> index 2dd95eb..6259a4b 100644
> >>>> --- a/fs/nfsd/nfs3proc.c
> >>>> +++ b/fs/nfsd/nfs3proc.c
> >>>> @@ -283,6 +283,16 @@
> >>>> struct nfsd3_diropres *resp = rqstp->rq_resp;
> >>>> __be32 nfserr;
> >>>>
> >>>> + if (argp->tlen == 0)
> >>>> + RETURN_STATUS(nfserr_inval);
> >>>> + if (argp->tlen > NFS3_MAXPATHLEN)
> >>>> + RETURN_STATUS(nfserr_nametoolong);
> >>>> +
> >>>> + argp->tname = svc_fill_symlink_pathname(rqstp, &argp->first,
> >>>> + argp->tlen);
> >>>> + if (IS_ERR(argp->tname))
> >>>> + RETURN_STATUS(nfserrno(PTR_ERR(argp->tname)));
> >>>> +
> >>>> dprintk("nfsd: SYMLINK(3) %s %.*s -> %.*s\n",
> >>>> SVCFH_fmt(&argp->ffh),
> >>>> argp->flen, argp->fname,
> >>>> diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
> >>>> index 240cdb0e..78b555b 100644
> >>>> --- a/fs/nfsd/nfs3xdr.c
> >>>> +++ b/fs/nfsd/nfs3xdr.c
> >>>> @@ -452,51 +452,24 @@ void fill_post_wcc(struct svc_fh *fhp)
> >>>> nfs3svc_decode_symlinkargs(struct svc_rqst *rqstp, __be32 *p)
> >>>> {
> >>>> struct nfsd3_symlinkargs *args = rqstp->rq_argp;
> >>>> - unsigned int len, avail;
> >>>> - char *old, *new;
> >>>> - struct kvec *vec;
> >>>> + char *base = (char *)p;
> >>>> + size_t dlen;
> >>>>
> >>>> if (!(p = decode_fh(p, &args->ffh)) ||
> >>>> - !(p = decode_filename(p, &args->fname, &args->flen))
> >>>> - )
> >>>> + !(p = decode_filename(p, &args->fname, &args->flen)))
> >>>> return 0;
> >>>> p = decode_sattr3(p, &args->attrs);
> >>>>
> >>>> - /* now decode the pathname, which might be larger than the first page.
> >>>> - * As we have to check for nul's anyway, we copy it into a new page
> >>>> - * This page appears in the rq_res.pages list, but as pages_len is always
> >>>> - * 0, it won't get in the way
> >>>> - */
> >>>> - len = ntohl(*p++);
> >>>> - if (len == 0 || len > NFS3_MAXPATHLEN || len >= PAGE_SIZE)
> >>>> - return 0;
> >>>> - args->tname = new = page_address(*(rqstp->rq_next_page++));
> >>>> - args->tlen = len;
> >>>> - /* first copy and check from the first page */
> >>>> - old = (char*)p;
> >>>> - vec = &rqstp->rq_arg.head[0];
> >>>> - if ((void *)old > vec->iov_base + vec->iov_len)
> >>>> - return 0;
> >>>> - avail = vec->iov_len - (old - (char*)vec->iov_base);
> >>>> - while (len && avail && *old) {
> >>>> - *new++ = *old++;
> >>>> - len--;
> >>>> - avail--;
> >>>> - }
> >>>> - /* now copy next page if there is one */
> >>>> - if (len && !avail && rqstp->rq_arg.page_len) {
> >>>> - avail = min_t(unsigned int, rqstp->rq_arg.page_len, PAGE_SIZE);
> >>>> - old = page_address(rqstp->rq_arg.pages[0]);
> >>>> - }
> >>>> - while (len && avail && *old) {
> >>>> - *new++ = *old++;
> >>>> - len--;
> >>>> - avail--;
> >>>> - }
> >>>> - *new = '\0';
> >>>> - if (len)
> >>>> - return 0;
> >>>> + args->tlen = ntohl(*p++);
> >>>>
> >>>> + args->first.iov_base = p;
> >>>> + args->first.iov_len = rqstp->rq_arg.head[0].iov_len;
> >>>> + args->first.iov_len -= (char *)p - base;
> >>>> +
> >>>> + dlen = args->first.iov_len + rqstp->rq_arg.page_len +
> >>>> + rqstp->rq_arg.tail[0].iov_len;
> >>>> + if (dlen < XDR_QUADLEN(args->tlen) << 2)
> >>>> + return 0;
> >>>> return 1;
> >>>> }
> >>>>
> >>>> diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
> >>>> index 5029b96..36bd1f7 100644
> >>>> --- a/fs/nfsd/nfs4proc.c
> >>>> +++ b/fs/nfsd/nfs4proc.c
> >>>> @@ -605,6 +605,13 @@ static void gen_boot_verifier(nfs4_verifier *verifier, struct net *net)
> >>>>
> >>>> switch (create->cr_type) {
> >>>> case NF4LNK:
> >>>> + if (create->cr_datalen > NFS4_MAXPATHLEN)
> >>>> + return nfserr_nametoolong;
> >>>> + create->cr_data =
> >>>> + svc_fill_symlink_pathname(rqstp, &create->cr_first,
> >>>> + create->cr_datalen);
> >>>> + if (IS_ERR(create->cr_data))
> >>>> + return nfserrno(PTR_ERR(create->cr_data));
> >>>> status = nfsd_symlink(rqstp, &cstate->current_fh,
> >>>> create->cr_name, create->cr_namelen,
> >>>> create->cr_data, &resfh);
> >>>> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> >>>> index bd25230..d05384e 100644
> >>>> --- a/fs/nfsd/nfs4xdr.c
> >>>> +++ b/fs/nfsd/nfs4xdr.c
> >>>> @@ -648,6 +648,7 @@ static __be32 nfsd4_decode_bind_conn_to_session(struct nfsd4_compoundargs *argp,
> >>>> static __be32
> >>>> nfsd4_decode_create(struct nfsd4_compoundargs *argp, struct nfsd4_create *create)
> >>>> {
> >>>> + struct kvec *head;
> >>>> DECODE_HEAD;
> >>>>
> >>>> READ_BUF(4);
> >>>> @@ -656,10 +657,13 @@ static __be32 nfsd4_decode_bind_conn_to_session(struct nfsd4_compoundargs *argp,
> >>>> case NF4LNK:
> >>>> READ_BUF(4);
> >>>> create->cr_datalen = be32_to_cpup(p++);
> >>>> + if (create->cr_datalen == 0)
> >>>> + return nfserr_inval;
> >>>> + head = argp->rqstp->rq_arg.head;
> >>>> + create->cr_first.iov_base = p;
> >>>> + create->cr_first.iov_len = head->iov_len;
> >>>> + create->cr_first.iov_len -= (char *)p - (char *)head->iov_base;
> >>>> READ_BUF(create->cr_datalen);
> >>>> - create->cr_data = svcxdr_dupstr(argp, p, create->cr_datalen);
> >>>> - if (!create->cr_data)
> >>>> - return nfserr_jukebox;
> >>>> break;
> >>>> case NF4BLK:
> >>>> case NF4CHR:
> >>>> diff --git a/fs/nfsd/nfsproc.c b/fs/nfsd/nfsproc.c
> >>>> index 1995ea6..f107f9f 100644
> >>>> --- a/fs/nfsd/nfsproc.c
> >>>> +++ b/fs/nfsd/nfsproc.c
> >>>> @@ -449,17 +449,19 @@
> >>>> struct svc_fh newfh;
> >>>> __be32 nfserr;
> >>>>
> >>>> + if (argp->tlen > NFS_MAXPATHLEN)
> >>>> + return nfserr_nametoolong;
> >>>> +
> >>>> + argp->tname = svc_fill_symlink_pathname(rqstp, &argp->first,
> >>>> + argp->tlen);
> >>>> + if (IS_ERR(argp->tname))
> >>>> + return nfserrno(PTR_ERR(argp->tname));
> >>>> +
> >>>> dprintk("nfsd: SYMLINK %s %.*s -> %.*s\n",
> >>>> SVCFH_fmt(&argp->ffh), argp->flen, argp->fname,
> >>>> argp->tlen, argp->tname);
> >>>>
> >>>> fh_init(&newfh, NFS_FHSIZE);
> >>>> - /*
> >>>> - * Crazy hack: the request fits in a page, and already-decoded
> >>>> - * attributes follow argp->tname, so it's safe to just write a
> >>>> - * null to ensure it's null-terminated:
> >>>> - */
> >>>> - argp->tname[argp->tlen] = '\0';
> >>>> nfserr = nfsd_symlink(rqstp, &argp->ffh, argp->fname, argp->flen,
> >>>> argp->tname, &newfh);
> >>>>
> >>>> diff --git a/fs/nfsd/nfsxdr.c b/fs/nfsd/nfsxdr.c
> >>>> index 165e25e..8fcd047 100644
> >>>> --- a/fs/nfsd/nfsxdr.c
> >>>> +++ b/fs/nfsd/nfsxdr.c
> >>>> @@ -71,22 +71,6 @@ __be32 *nfs2svc_decode_fh(__be32 *p, struct svc_fh *fhp)
> >>>> }
> >>>>
> >>>> static __be32 *
> >>>> -decode_pathname(__be32 *p, char **namp, unsigned int *lenp)
> >>>> -{
> >>>> - char *name;
> >>>> - unsigned int i;
> >>>> -
> >>>> - if ((p = xdr_decode_string_inplace(p, namp, lenp, NFS_MAXPATHLEN)) != NULL) {
> >>>> - for (i = 0, name = *namp; i < *lenp; i++, name++) {
> >>>> - if (*name == '\0')
> >>>> - return NULL;
> >>>> - }
> >>>> - }
> >>>> -
> >>>> - return p;
> >>>> -}
> >>>> -
> >>>> -static __be32 *
> >>>> decode_sattr(__be32 *p, struct iattr *iap)
> >>>> {
> >>>> u32 tmp, tmp1;
> >>>> @@ -383,14 +367,39 @@ __be32 *nfs2svc_encode_fattr(struct svc_rqst *rqstp, __be32 *p, struct svc_fh *f
> >>>> nfssvc_decode_symlinkargs(struct svc_rqst *rqstp, __be32 *p)
> >>>> {
> >>>> struct nfsd_symlinkargs *args = rqstp->rq_argp;
> >>>> + char *base = (char *)p;
> >>>> + size_t xdrlen;
> >>>>
> >>>> if ( !(p = decode_fh(p, &args->ffh))
> >>>> - || !(p = decode_filename(p, &args->fname, &args->flen))
> >>>> - || !(p = decode_pathname(p, &args->tname, &args->tlen)))
> >>>> + || !(p = decode_filename(p, &args->fname, &args->flen)))
> >>>> return 0;
> >>>> - p = decode_sattr(p, &args->attrs);
> >>>>
> >>>> - return xdr_argsize_check(rqstp, p);
> >>>> + args->tlen = ntohl(*p++);
> >>>> + if (args->tlen == 0)
> >>>> + return 0;
> >>>> +
> >>>> + args->first.iov_base = p;
> >>>> + args->first.iov_len = rqstp->rq_arg.head[0].iov_len;
> >>>> + args->first.iov_len -= (char *)p - base;
> >>>> +
> >>>> + /* This request is never larger than a page. Therefore,
> >>>> + * transport will deliver either:
> >>>> + * 1. pathname in the pagelist -> sattr is in the tail.
> >>>> + * 2. everything in the head buffer -> sattr is in the head.
> >>>> + */
> >>>> + if (rqstp->rq_arg.page_len) {
> >>>> + if (args->tlen != rqstp->rq_arg.page_len)
> >>>> + return 0;
> >>>> + p = rqstp->rq_arg.tail[0].iov_base;
> >>>> + } else {
> >>>> + xdrlen = XDR_QUADLEN(args->tlen);
> >>>> + if (xdrlen > args->first.iov_len - (8 * sizeof(__be32)))
> >>>> + return 0;
> >>>> + p += xdrlen;
> >>>> + }
> >>>> + decode_sattr(p, &args->attrs);
> >>>> +
> >>>> + return 1;
> >>>> }
> >>>>
> >>>> int
> >>>> diff --git a/fs/nfsd/xdr.h b/fs/nfsd/xdr.h
> >>>> index a765c41..ea7cca3 100644
> >>>> --- a/fs/nfsd/xdr.h
> >>>> +++ b/fs/nfsd/xdr.h
> >>>> @@ -72,6 +72,7 @@ struct nfsd_symlinkargs {
> >>>> char * tname;
> >>>> unsigned int tlen;
> >>>> struct iattr attrs;
> >>>> + struct kvec first;
> >>>> };
> >>>>
> >>>> struct nfsd_readdirargs {
> >>>> diff --git a/fs/nfsd/xdr3.h b/fs/nfsd/xdr3.h
> >>>> index deccf7f..2cb29e9 100644
> >>>> --- a/fs/nfsd/xdr3.h
> >>>> +++ b/fs/nfsd/xdr3.h
> >>>> @@ -90,6 +90,7 @@ struct nfsd3_symlinkargs {
> >>>> char * tname;
> >>>> unsigned int tlen;
> >>>> struct iattr attrs;
> >>>> + struct kvec first;
> >>>> };
> >>>>
> >>>> struct nfsd3_readdirargs {
> >>>> diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h
> >>>> index d56219d..b485cd1 100644
> >>>> --- a/fs/nfsd/xdr4.h
> >>>> +++ b/fs/nfsd/xdr4.h
> >>>> @@ -110,6 +110,7 @@ struct nfsd4_create {
> >>>> struct {
> >>>> u32 datalen;
> >>>> char *data;
> >>>> + struct kvec first;
> >>>> } link; /* NF4LNK */
> >>>> struct {
> >>>> u32 specdata1;
> >>>> @@ -124,6 +125,7 @@ struct nfsd4_create {
> >>>> };
> >>>> #define cr_datalen u.link.datalen
> >>>> #define cr_data u.link.data
> >>>> +#define cr_first u.link.first
> >>>> #define cr_specdata1 u.dev.specdata1
> >>>> #define cr_specdata2 u.dev.specdata2
> >>>>
> >>>> diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
> >>>> index 238b9ae..fd5846e 100644
> >>>> --- a/include/linux/sunrpc/svc.h
> >>>> +++ b/include/linux/sunrpc/svc.h
> >>>> @@ -495,6 +495,8 @@ int svc_register(const struct svc_serv *, struct net *, const int,
> >>>> char * svc_print_addr(struct svc_rqst *, char *, size_t);
> >>>> unsigned int svc_fill_write_vector(struct svc_rqst *rqstp,
> >>>> struct kvec *first, size_t total);
> >>>> +char *svc_fill_symlink_pathname(struct svc_rqst *rqstp,
> >>>> + struct kvec *first, size_t total);
> >>>>
> >>>> #define RPC_MAX_ADDRBUFLEN (63U)
> >>>>
> >>>> diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
> >>>> index 759b668..fc93406 100644
> >>>> --- a/net/sunrpc/svc.c
> >>>> +++ b/net/sunrpc/svc.c
> >>>> @@ -1578,3 +1578,70 @@ unsigned int svc_fill_write_vector(struct svc_rqst *rqstp, struct kvec *first,
> >>>> return i;
> >>>> }
> >>>> EXPORT_SYMBOL_GPL(svc_fill_write_vector);
> >>>> +
> >>>> +/**
> >>>> + * svc_fill_symlink_pathname - Construct pathname argument for VFS symlink call
> >>>> + * @rqstp: svc_rqst to operate on
> >>>> + * @first: buffer containing first section of pathname
> >>>> + * @total: total length of the pathname argument
> >>>> + *
> >>>> + * Returns pointer to a NUL-terminated string, or an ERR_PTR. The buffer is
> >>>> + * released automatically when @rqstp is recycled.
> >>>> + */
> >>>> +char *svc_fill_symlink_pathname(struct svc_rqst *rqstp, struct kvec *first,
> >>>> + size_t total)
> >>>> +{
> >>>> + struct xdr_buf *arg = &rqstp->rq_arg;
> >>>> + struct page **pages;
> >>>> + char *result;
> >>>> +
> >>>> + /* VFS API demands a NUL-terminated pathname. This function
> >>>> + * uses a page from @rqstp as the pathname buffer, to enable
> >>>> + * direct placement. Thus the total buffer size is PAGE_SIZE.
> >>>> + * Space in this buffer for NUL-termination requires that we
> >>>> + * cap the size of the returned symlink pathname just a
> >>>> + * little early.
> >>>> + */
> >>>> + if (total > PAGE_SIZE - 1)
> >>>> + return ERR_PTR(-ENAMETOOLONG);
> >>>> +
> >>>> + /* Some types of transport can present the pathname entirely
> >>>> + * in rq_arg.pages. If not, then copy the pathname into one
> >>>> + * page.
> >>>> + */
> >>>> + pages = arg->pages;
> >>>> + WARN_ON_ONCE(arg->page_base != 0);
> >>>> + if (first->iov_base == 0) {
> >>>> + result = page_address(*pages);
> >>>> + result[total] = '\0';
> >>>> + } else {
> >>>> + size_t len, remaining;
> >>>> + char *dst;
> >>>> +
> >>>> + result = page_address(*(rqstp->rq_next_page++));
> >>>> + dst = result;
> >>>> + remaining = total;
> >>>> +
> >>>> + len = min_t(size_t, total, first->iov_len);
> >>>> + memcpy(dst, first->iov_base, len);
> >>>> + dst += len;
> >>>> + remaining -= len;
> >>>> +
> >>>> + /* No more than one page left */
> >>>> + if (remaining) {
> >>>> + len = min_t(size_t, remaining, PAGE_SIZE);
> >>>> + memcpy(dst, page_address(*pages), len);
> >>>> + dst += len;
> >>>> + }
> >>>> +
> >>>> + *dst = '\0';
> >>>> + }
> >>>> +
> >>>> + /* Sanity check: we don't allow the pathname argument to
> >>>> + * contain a NUL byte.
> >>>> + */
> >>>> + if (strlen(result) != total)
> >>>> + return ERR_PTR(-EINVAL);
> >>>> + return result;
> >>>> +}
> >>>> +EXPORT_SYMBOL_GPL(svc_fill_symlink_pathname);
> >>
> >> --
> >> Chuck Lever
>
> --
> Chuck Lever
>
>
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