svcrdma expects that the payload falls precisely into the xdr_buf
page vector. Adding "xdr->iov = NULL" forces xdr_reserve_space to
always use pages from xdr->buf->pages when calling nfsd_readv.
This code is called only when fops->splice_read is missing or when
RQ_SPLICE_OK is clear, so it's not a noticeable problem in many
common cases.
Fixes: b04209806384 ("nfsd4: allow exotic read compounds")
Buglink: https://bugzilla.kernel.org/show_bug.cgi?id=198053
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
fs/nfsd/nfs4xdr.c | 15 ++++++---------
1 file changed, 6 insertions(+), 9 deletions(-)
diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 75d1fc13a9c9..92a6ada60932 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -3521,17 +3521,14 @@ static __be32 nfsd4_encode_readv(struct nfsd4_compoundres *resp,
u32 zzz = 0;
int pad;
+ /* Ensure xdr_reserve_space behaves itself */
+ if (xdr->iov == xdr->buf->head) {
+ xdr->iov = NULL;
+ xdr->end = xdr->p;
+ }
+
len = maxcount;
v = 0;
-
- thislen = min_t(long, len, ((void *)xdr->end - (void *)xdr->p));
- p = xdr_reserve_space(xdr, (thislen+3)&~3);
- WARN_ON_ONCE(!p);
- resp->rqstp->rq_vec[v].iov_base = p;
- resp->rqstp->rq_vec[v].iov_len = thislen;
- v++;
- len -= thislen;
-
while (len) {
thislen = min_t(long, len, PAGE_SIZE);
p = xdr_reserve_space(xdr, (thislen+3)&~3);
