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-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);