[PATCH 9/8] nfsd: handle arbitrary page array layouts in nfsd_cache_crc

[Jeff Layton <jlayton@redhat.com>]

The original code didn't handle the case where the page_base was close
to the end of the page. In practice, page_base is always 0 on receive,
so it's not a problem today, but let's future-proof this in the event
that it ever is.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
---
 fs/nfsd/nfscache.c | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c
index cb655f3..e705fea 100644
--- a/fs/nfsd/nfscache.c
+++ b/fs/nfsd/nfscache.c
@@ -248,6 +248,8 @@ nfsd_reply_cache_shrink(struct shrinker *shrink, struct shrink_control *sc)
 static u32
 nfsd_cache_crc(struct xdr_buf *buf)
 {
+	int idx;
+	unsigned int base;
 	u32 crc;
 	const unsigned char *p = buf->head[0].iov_base;
 	size_t csum_len = min_t(size_t, buf->head[0].iov_len + buf->page_len,
@@ -258,13 +260,18 @@ nfsd_cache_crc(struct xdr_buf *buf)
 	crc = crc32(crc_seed, p, len);
 	csum_len -= len;
 
-	/* Nothing left */
-	if (!csum_len)
-		return crc;
-
-	/* checksum the rest from the page_array */
-	p = page_address(buf->pages[0]) + buf->page_base;
-	return crc32(crc, p, csum_len);
+	/* Continue into page array */
+	idx = buf->page_base / PAGE_SIZE;
+	base = buf->page_base & ~PAGE_MASK;
+	while (csum_len) {
+		p = page_address(buf->pages[idx]) + base;
+		len = min(PAGE_SIZE - base, csum_len);
+		crc = crc32(crc, p, len);
+		csum_len -= len;
+		base = 0;
+		++idx;
+	}
+	return crc;
 }
 
 /*
-- 
1.7.11.7