Revert "nfs: replace nfs_add_stats with nfs_inc_stats when add one"

This reverts commit 5a254d08.

Since commit 5a254d08 ("nfs: replace nfs_add_stats with
nfs_inc_stats when add one"), nfs_readpage and nfs_do_writepage use
nfs_inc_stats to increment NFSIOS_READPAGES and NFSIOS_WRITEPAGES
instead of nfs_add_stats.

However nfs_inc_stats does not do the same thing as nfs_add_stats with
value 1 because these functions work on distinct stats:
nfs_inc_stats increments stats from "enum nfs_stat_eventcounters" (in
server->io_stats->events) and nfs_add_stats those from "enum
nfs_stat_bytecounters" (in server->io_stats->bytes).
Signed-off-by: NNicolas Iooss <nicolas.iooss_linux@m4x.org>
Fixes: 5a254d08 ("nfs: replace nfs_add_stats with nfs_inc_stats...")
Cc: stable@vger.kernel.org # 3.19+
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

fs/nfs/read.c

@@ -284,7 +284,7 @@ int nfs_readpage(struct file *file, struct page *page)
 	dprintk("NFS: nfs_readpage (%p %ld@%lu)\n",
 		page, PAGE_CACHE_SIZE, page_file_index(page));
 	nfs_inc_stats(inode, NFSIOS_VFSREADPAGE);
-	nfs_inc_stats(inode, NFSIOS_READPAGES);
+	nfs_add_stats(inode, NFSIOS_READPAGES, 1);
 
 	/*
 	 * Try to flush any pending writes to the file..

fs/nfs/write.c

@@ -580,7 +580,7 @@ static int nfs_do_writepage(struct page *page, struct writeback_control *wbc, st
 	int ret;
 
 	nfs_inc_stats(inode, NFSIOS_VFSWRITEPAGE);
-	nfs_inc_stats(inode, NFSIOS_WRITEPAGES);
+	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);