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>

diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
index afcab00..e30d928 100644 (file)
--- 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;