From 0baa1bd9b6da7161dc1773b1dfce3adfd37d675f Mon Sep 17 00:00:00 2001 From: Alex Elder Date: Fri, 29 Mar 2013 14:28:03 -0500 Subject: [PATCH] libceph: be explicit in masking bottom 16 bits In ceph_osdc_build_request() there is a call to cpu_to_le16() which provides a 64-bit value as its argument. Because of the implied byte swapping going on it looked pretty suspect to me. At the moment it turns out the behavior is well defined, but masking off those bottom bits explicitly eliminates this distraction, and is in fact more directly related to the purpose of the message header's data_off field. This resolves: http://tracker.ceph.com/issues/4125 Signed-off-by: Alex Elder Reviewed-by: Josh Durgin --- net/ceph/osd_client.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c index 3b6657fe99b1..015bf9f64da7 100644 --- a/net/ceph/osd_client.c +++ b/net/ceph/osd_client.c @@ -419,8 +419,18 @@ void ceph_osdc_build_request(struct ceph_osd_request *req, p += 4; /* data */ - if (flags & CEPH_OSD_FLAG_WRITE) - req->r_request->hdr.data_off = cpu_to_le16(off); + if (flags & CEPH_OSD_FLAG_WRITE) { + u16 data_off; + + /* + * The header "data_off" is a hint to the receiver + * allowing it to align received data into its + * buffers such that there's no need to re-copy + * it before writing it to disk (direct I/O). + */ + data_off = (u16) (off & 0xffff); + req->r_request->hdr.data_off = cpu_to_le16(data_off); + } req->r_request->hdr.data_len = cpu_to_le32(data_len); BUG_ON(p > msg->front.iov_base + msg->front.iov_len); -- GitLab