Add an iov_iter to the read subrequest and set it up to define the
destination buffer to write into.  This will allow future patches to point
to a bounce buffer instead for purposes of handling oversize writes,
decryption (where we want to save the encrypted data to the cache) and
decompression.

Signed-off-by: David Howells <dhowe...@redhat.com>
---

 fs/afs/file.c          |    6 +-----
 fs/netfs/read_helper.c |    5 ++++-
 include/linux/netfs.h  |    2 ++
 3 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/fs/afs/file.c b/fs/afs/file.c
index c9c21ad0e7c9..ca529f23515a 100644
--- a/fs/afs/file.c
+++ b/fs/afs/file.c
@@ -319,11 +319,7 @@ static void afs_req_issue_op(struct netfs_read_subrequest 
*subreq)
        fsreq->len      = subreq->len   - subreq->transferred;
        fsreq->key      = subreq->rreq->netfs_priv;
        fsreq->vnode    = vnode;
-       fsreq->iter     = &fsreq->def_iter;
-
-       iov_iter_xarray(&fsreq->def_iter, READ,
-                       &fsreq->vnode->vfs_inode.i_mapping->i_pages,
-                       fsreq->pos, fsreq->len);
+       fsreq->iter     = &subreq->iter;
 
        afs_fetch_data(fsreq->vnode, fsreq);
 }
diff --git a/fs/netfs/read_helper.c b/fs/netfs/read_helper.c
index 0b6cd3b8734c..715f3e9c380d 100644
--- a/fs/netfs/read_helper.c
+++ b/fs/netfs/read_helper.c
@@ -150,7 +150,7 @@ static void netfs_clear_unread(struct netfs_read_subrequest 
*subreq)
 {
        struct iov_iter iter;
 
-       iov_iter_xarray(&iter, WRITE, &subreq->rreq->mapping->i_pages,
+       iov_iter_xarray(&iter, READ, &subreq->rreq->mapping->i_pages,
                        subreq->start + subreq->transferred,
                        subreq->len   - subreq->transferred);
        iov_iter_zero(iov_iter_count(&iter), &iter);
@@ -745,6 +745,9 @@ netfs_rreq_prepare_read(struct netfs_read_request *rreq,
        if (WARN_ON(subreq->len == 0))
                source = NETFS_INVALID_READ;
 
+       iov_iter_xarray(&subreq->iter, READ, &rreq->mapping->i_pages,
+                       subreq->start, subreq->len);
+
 out:
        subreq->source = source;
        trace_netfs_sreq(subreq, netfs_sreq_trace_prepare);
diff --git a/include/linux/netfs.h b/include/linux/netfs.h
index fe9887768292..5e4fafcc9480 100644
--- a/include/linux/netfs.h
+++ b/include/linux/netfs.h
@@ -17,6 +17,7 @@
 #include <linux/workqueue.h>
 #include <linux/fs.h>
 #include <linux/pagemap.h>
+#include <linux/uio.h>
 
 /*
  * Overload PG_private_2 to give us PG_fscache - this is used to indicate that
@@ -112,6 +113,7 @@ struct netfs_cache_resources {
 struct netfs_read_subrequest {
        struct netfs_read_request *rreq;        /* Supervising read request */
        struct list_head        rreq_link;      /* Link in rreq->subrequests */
+       struct iov_iter         iter;           /* Iterator for this subrequest 
*/
        loff_t                  start;          /* Where to start the I/O */
        size_t                  len;            /* Size of the I/O */
        size_t                  transferred;    /* Amount of data transferred */


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