NFS: Fix up page writeback accounting

Currently, we are crediting all the calls to nfs_writepages_callback()
(i.e. the nfs_writepages() callback) to nfs_writepage(). Aside from
being inconsistent with the behaviour of the equivalent readpage/readpages
accounting, this also means that we cannot distinguish between bulk writes
and single page writebacks (which confuses the 'nfsiostat -p' tool).

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 72624dc..cfa4776 100644 (file)
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -569,19 +569,17 @@ static int nfs_page_async_flush(struct nfs_pageio_descriptor *pgio,
        if (!nfs_pageio_add_request(pgio, req)) {
                nfs_redirty_request(req);
                ret = pgio->pg_error;
-       }
+       } else
+               nfs_add_stats(page_file_mapping(page)->host,
+                               NFSIOS_WRITEPAGES, 1);
 out:
        return ret;
 }
 
 static int nfs_do_writepage(struct page *page, struct writeback_control *wbc, struct nfs_pageio_descriptor *pgio)
 {
-       struct inode *inode = page_file_mapping(page)->host;
        int ret;
 
-       nfs_inc_stats(inode, NFSIOS_VFSWRITEPAGE);
-       nfs_add_stats(inode, NFSIOS_WRITEPAGES, 1);
-
        nfs_pageio_cond_complete(pgio, page_file_index(page));
        ret = nfs_page_async_flush(pgio, page, wbc->sync_mode == WB_SYNC_NONE);
        if (ret == -EAGAIN) {
@@ -597,9 +595,11 @@ static int nfs_do_writepage(struct page *page, struct writeback_control *wbc, st
 static int nfs_writepage_locked(struct page *page, struct writeback_control *wbc)
 {
        struct nfs_pageio_descriptor pgio;
+       struct inode *inode = page_file_mapping(page)->host;
        int err;
 
-       nfs_pageio_init_write(&pgio, page->mapping->host, wb_priority(wbc),
+       nfs_inc_stats(inode, NFSIOS_VFSWRITEPAGE);
+       nfs_pageio_init_write(&pgio, inode, wb_priority(wbc),
                                false, &nfs_async_write_completion_ops);
        err = nfs_do_writepage(page, wbc, &pgio);
        nfs_pageio_complete(&pgio);