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authorAlex Elder <elder@inktank.com>2013-03-29 23:28:03 +0400
committerSage Weil <sage@inktank.com>2013-05-02 08:17:41 +0400
commit0baa1bd9b6da7161dc1773b1dfce3adfd37d675f (patch)
tree30986227e5b5bdc0884066015ad78a3ce04bc79c /net/ceph
parent56fc5659162965ce3018a34c6bb8a022f3a3b33c (diff)
downloadlinux-0baa1bd9b6da7161dc1773b1dfce3adfd37d675f.tar.xz
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 <elder@inktank.com> Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
Diffstat (limited to 'net/ceph')
-rw-r--r--net/ceph/osd_client.c14
1 files 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);