summaryrefslogtreecommitdiff
path: root/net/sunrpc/xdr.c
diff options
context:
space:
mode:
authorAnna Schumaker <Anna.Schumaker@Netapp.com>2020-08-17 19:53:06 +0300
committerJ. Bruce Fields <bfields@redhat.com>2020-09-26 01:01:27 +0300
commit403217f30418c808600e3e8e345413ba5cc15676 (patch)
tree5513e684750faaaa6cf321498478809d87bf4b67 /net/sunrpc/xdr.c
parent3caf91757ced158e6c4a44d8b105bd7b3e1767d8 (diff)
downloadlinux-403217f30418c808600e3e8e345413ba5cc15676.tar.xz
SUNRPC/NFSD: Implement xdr_reserve_space_vec()
Reserving space for a large READ payload requires special handling when reserving space in the xdr buffer pages. One problem we can have is use of the scratch buffer, which is used to get a pointer to a contiguous region of data up to PAGE_SIZE. When using the scratch buffer, calls to xdr_commit_encode() shift the data to it's proper alignment in the xdr buffer. If we've reserved several pages in a vector, then this could potentially invalidate earlier pointers and result in incorrect READ data being sent to the client. I get around this by looking at the amount of space left in the current page, and never reserve more than that for each entry in the read vector. This lets us place data directly where it needs to go in the buffer pages. Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com> Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Diffstat (limited to 'net/sunrpc/xdr.c')
-rw-r--r--net/sunrpc/xdr.c45
1 files changed, 45 insertions, 0 deletions
diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
index 3bd5bef02996..b45af330f9f3 100644
--- a/net/sunrpc/xdr.c
+++ b/net/sunrpc/xdr.c
@@ -648,6 +648,51 @@ __be32 * xdr_reserve_space(struct xdr_stream *xdr, size_t nbytes)
}
EXPORT_SYMBOL_GPL(xdr_reserve_space);
+
+/**
+ * xdr_reserve_space_vec - Reserves a large amount of buffer space for sending
+ * @xdr: pointer to xdr_stream
+ * @vec: pointer to a kvec array
+ * @nbytes: number of bytes to reserve
+ *
+ * Reserves enough buffer space to encode 'nbytes' of data and stores the
+ * pointers in 'vec'. The size argument passed to xdr_reserve_space() is
+ * determined based on the number of bytes remaining in the current page to
+ * avoid invalidating iov_base pointers when xdr_commit_encode() is called.
+ */
+int xdr_reserve_space_vec(struct xdr_stream *xdr, struct kvec *vec, size_t nbytes)
+{
+ int thislen;
+ int v = 0;
+ __be32 *p;
+
+ /*
+ * svcrdma requires every READ payload to start somewhere
+ * in xdr->pages.
+ */
+ if (xdr->iov == xdr->buf->head) {
+ xdr->iov = NULL;
+ xdr->end = xdr->p;
+ }
+
+ while (nbytes) {
+ thislen = xdr->buf->page_len % PAGE_SIZE;
+ thislen = min_t(size_t, nbytes, PAGE_SIZE - thislen);
+
+ p = xdr_reserve_space(xdr, thislen);
+ if (!p)
+ return -EIO;
+
+ vec[v].iov_base = p;
+ vec[v].iov_len = thislen;
+ v++;
+ nbytes -= thislen;
+ }
+
+ return v;
+}
+EXPORT_SYMBOL_GPL(xdr_reserve_space_vec);
+
/**
* xdr_truncate_encode - truncate an encode buffer
* @xdr: pointer to xdr_stream