NFS: Allow the nfs_pageio_descriptor to signal that a re-coalesce is needed

If an attempt to do pNFS fails, and we have to fall back to writing through
the MDS, then we may want to re-coalesce the requests that we already have
since the block size for the MDS read/writes may be different to that of
the DS read/writes.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index d421e19..7139dbf 100644 (file)
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -240,6 +240,7 @@ void nfs_pageio_init(struct nfs_pageio_descriptor *desc,
        desc->pg_bsize = bsize;
        desc->pg_base = 0;
        desc->pg_moreio = 0;
+       desc->pg_recoalesce = 0;
        desc->pg_inode = inode;
        desc->pg_ops = pg_ops;
        desc->pg_ioflags = io_flags;
@@ -331,7 +332,7 @@ static void nfs_pageio_doio(struct nfs_pageio_descriptor *desc)
  * Returns true if the request 'req' was successfully coalesced into the
  * existing list of pages 'desc'.
  */
-int nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
+static int __nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
                           struct nfs_page *req)
 {
        while (!nfs_pageio_do_add_request(desc, req)) {
@@ -340,17 +341,67 @@ int nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
                if (desc->pg_error < 0)
                        return 0;
                desc->pg_moreio = 0;
+               if (desc->pg_recoalesce)
+                       return 0;
        }
        return 1;
 }
 
+static int nfs_do_recoalesce(struct nfs_pageio_descriptor *desc)
+{
+       LIST_HEAD(head);
+
+       do {
+               list_splice_init(&desc->pg_list, &head);
+               desc->pg_bytes_written -= desc->pg_count;
+               desc->pg_count = 0;
+               desc->pg_base = 0;
+               desc->pg_recoalesce = 0;
+
+               while (!list_empty(&head)) {
+                       struct nfs_page *req;
+
+                       req = list_first_entry(&head, struct nfs_page, wb_list);
+                       nfs_list_remove_request(req);
+                       if (__nfs_pageio_add_request(desc, req))
+                               continue;
+                       if (desc->pg_error < 0)
+                               return 0;
+                       break;
+               }
+       } while (desc->pg_recoalesce);
+       return 1;
+}
+
+int nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
+               struct nfs_page *req)
+{
+       int ret;
+
+       do {
+               ret = __nfs_pageio_add_request(desc, req);
+               if (ret)
+                       break;
+               if (desc->pg_error < 0)
+                       break;
+               ret = nfs_do_recoalesce(desc);
+       } while (ret);
+       return ret;
+}
+
 /**
  * nfs_pageio_complete - Complete I/O on an nfs_pageio_descriptor
  * @desc: pointer to io descriptor
  */
 void nfs_pageio_complete(struct nfs_pageio_descriptor *desc)
 {
-       nfs_pageio_doio(desc);
+       for (;;) {
+               nfs_pageio_doio(desc);
+               if (!desc->pg_recoalesce)
+                       break;
+               if (!nfs_do_recoalesce(desc))
+                       break;
+       }
 }
 
 /**
@@ -369,7 +420,7 @@ void nfs_pageio_cond_complete(struct nfs_pageio_descriptor *desc, pgoff_t index)
        if (!list_empty(&desc->pg_list)) {
                struct nfs_page *prev = nfs_list_entry(desc->pg_list.prev);
                if (index != prev->wb_index + 1)
-                       nfs_pageio_doio(desc);
+                       nfs_pageio_complete(desc);
        }
 }
 

diff --git a/include/linux/nfs_page.h b/include/linux/nfs_page.h
index db3194f..7241b2a 100644 (file)
--- a/include/linux/nfs_page.h
+++ b/include/linux/nfs_page.h
@@ -68,7 +68,8 @@ struct nfs_pageio_descriptor {
        size_t                  pg_count;
        size_t                  pg_bsize;
        unsigned int            pg_base;
-       char                    pg_moreio;
+       unsigned char           pg_moreio : 1,
+                               pg_recoalesce : 1;
 
        struct inode            *pg_inode;
        const struct nfs_pageio_ops *pg_ops;