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>

1 files changed, 54 insertions, 3 deletions

diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index d421e19557a5..7139dbf8784e 100644
--- 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);
         }
 }