NFS: Introduce iovec I/O helpers to fs/nfs/direct.c

Add helpers that iterate over multi-segment iovecs.  These will
be used to support multi-segment scatter/gather direct I/O in a
later patch.

Signed-off-by: Chuck Lever <cel@netapp.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 71 insertions, 0 deletions

diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
index afcab007a22b..e30d9285a566 100644
--- a/fs/nfs/direct.c
+++ b/fs/nfs/direct.c
@@ -355,6 +355,41 @@ static ssize_t nfs_direct_read_schedule(struct nfs_direct_req *dreq, unsigned lo
         return result < 0 ? (ssize_t) result : -EFAULT;
 }
 
+static ssize_t nfs_direct_read_schedule_iovec(struct nfs_direct_req *dreq,
+                                              const struct iovec *iov,
+                                              unsigned long nr_segs,
+                                              loff_t pos)
+{
+        ssize_t result = -EINVAL;
+        size_t requested_bytes = 0;
+        unsigned long seg;
+
+        get_dreq(dreq);
+
+        for (seg = 0; seg < nr_segs; seg++) {
+                const struct iovec *vec = &iov[seg];
+                result = nfs_direct_read_schedule(dreq,
+                                        (unsigned long)vec->iov_base,
+                                                  vec->iov_len, pos);
+                if (result < 0)
+                        break;
+                requested_bytes += result;
+                if ((size_t)result < vec->iov_len)
+                        break;
+                pos += vec->iov_len;
+        }
+
+        if (put_dreq(dreq))
+                nfs_direct_complete(dreq);
+
+        if (requested_bytes != 0)
+                return 0;
+
+        if (result < 0)
+                return result;
+        return -EIO;
+}
+
 static ssize_t nfs_direct_read(struct kiocb *iocb, unsigned long user_addr, size_t count, loff_t pos)
 {
         ssize_t result = 0;
@@ -697,6 +732,42 @@ static ssize_t nfs_direct_write_schedule(struct nfs_direct_req *dreq, unsigned l
         return result < 0 ? (ssize_t) result : -EFAULT;
 }
 
+static ssize_t nfs_direct_write_schedule_iovec(struct nfs_direct_req *dreq,
+                                               const struct iovec *iov,
+                                               unsigned long nr_segs,
+                                               loff_t pos, int sync)
+{
+        ssize_t result = 0;
+        size_t requested_bytes = 0;
+        unsigned long seg;
+
+        get_dreq(dreq);
+
+        for (seg = 0; seg < nr_segs; seg++) {
+                const struct iovec *vec = &iov[seg];
+                result = nfs_direct_write_schedule(dreq,
+                                        (unsigned long)vec->iov_base,
+                                                   vec->iov_len,
+                                                   pos, sync);
+                if (result < 0)
+                        break;
+                requested_bytes += result;
+                if ((size_t)result < vec->iov_len)
+                        break;
+                pos += vec->iov_len;
+        }
+
+        if (put_dreq(dreq))
+                nfs_direct_write_complete(dreq, dreq->inode);
+
+        if (requested_bytes != 0)
+                return 0;
+
+        if (result < 0)
+                return result;
+        return -EIO;
+}
+
 static ssize_t nfs_direct_write(struct kiocb *iocb, unsigned long user_addr, size_t count, loff_t pos)
 {
         ssize_t result = 0;