Re: mmap over nfs leads to excessive system load

[Trond Myklebust <trond.myklebust@fys.uio.no>]

On Wed, 2005-11-16 at 07:01 -0800, Kenny Simpson wrote:
> --- Trond Myklebust <trond.myklebust@fys.uio.no> wrote:
> > Anyhow, does the following patch help?
> 
> Unfortunately, not:
> 
> samples  %        symbol name
> 545009   15.2546  find_get_pages_tag

Argh... I totally missed the point there with the last patch. We should
be resyncing the page tag with the value of the PG_dirty flag...

OK, please back out the patch that I sent you, and try this one instead.

Cheers,
 Trond

------
NFS: resync to yet more writepage() changes...

 Ensure that we call clear_page_dirty() for pages that have been written
 via writepage().

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

 fs/nfs/write.c      |    2 ++
 include/linux/mm.h  |    1 +
 mm/page-writeback.c |   20 ++++++++++++++++++++
 3 files changed, 23 insertions(+), 0 deletions(-)

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 8f71e76..61ec355 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -213,6 +213,7 @@ static int nfs_writepage_sync(struct nfs
 	} while (count);
 	/* Update file length */
 	nfs_grow_file(page, offset, written);
+	clear_page_dirty_tag(page);
 	/* Set the PG_uptodate flag? */
 	nfs_mark_uptodate(page, offset, written);
 
@@ -238,6 +239,7 @@ static int nfs_writepage_async(struct nf
 		goto out;
 	/* Update file length */
 	nfs_grow_file(page, offset, count);
+	clear_page_dirty_tag(page);
 	/* Set the PG_uptodate flag? */
 	nfs_mark_uptodate(page, offset, count);
 	nfs_unlock_request(req);
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 1013a42..cb1cfe1 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -730,6 +730,7 @@ int redirty_page_for_writepage(struct wr
 int FASTCALL(set_page_dirty(struct page *page));
 int set_page_dirty_lock(struct page *page);
 int clear_page_dirty_for_io(struct page *page);
+int clear_page_dirty_tag(struct page *page);
 
 extern unsigned long do_mremap(unsigned long addr,
 			       unsigned long old_len, unsigned long new_len,
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 74138c9..65c58fa 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -751,6 +751,26 @@ int clear_page_dirty_for_io(struct page 
 	return TestClearPageDirty(page);
 }
 
+/*
+ * Clears the page dirty tag. See comment in clear_page_dirty_for_io()
+ */
+int clear_page_dirty_tag(struct page *page)
+{
+	struct address_space *mapping = page_mapping(page);
+
+	if (mapping) {
+		unsigned long flags;
+
+		write_lock_irqsave(&mapping->tree_lock, flags);
+		if (!PageDirty(page))
+			radix_tree_tag_clear(&mapping->page_tree,
+						page_index(page),
+						PAGECACHE_TAG_DIRTY);
+		write_unlock_irqrestore(&mapping->tree_lock, flags);
+	}
+}
+EXPORT_SYMBOL(clear_page_dirty_tag);
+
 int test_clear_page_writeback(struct page *page)
 {
 	struct address_space *mapping = page_mapping(page);