ceph: use vfs __set_page_dirty_nobuffers interface instead of doing it inside filesystem

Following we will begin to add memcg dirty page accounting around
__set_page_dirty_{buffers,nobuffers} in vfs layer, so we'd better use vfs interface to
avoid exporting those details to filesystems.

Since vfs set_page_dirty() should be called under page lock, here we don't need elaborate
codes to handle racy anymore, and two WARN_ON() are added to detect such exceptions.
Thanks very much for Sage and Yan Zheng's coaching!

I tested it in a two server's ceph environment that one is client and the other is
mds/osd/mon, and run the following fsx test from xfstests:

  ./fsx   1MB -N 50000 -p 10000 -l 1048576
  ./fsx  10MB -N 50000 -p 10000 -l 10485760
  ./fsx 100MB -N 50000 -p 10000 -l 104857600

The fsx does lots of mmap-read/mmap-write/truncate operations and the tests completed
successfully without triggering any of WARN_ON.

Signed-off-by: Sha Zhengju <handai.szj@taobao.com>
Reviewed-by: Sage Weil <sage@inktank.com>

1 files changed, 14 insertions, 29 deletions

diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index cb78ce81d6a6..3bed7da38326 100644
--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -70,15 +70,16 @@ static int ceph_set_page_dirty(struct page *page)
         struct address_space *mapping = page->mapping;
         struct inode *inode;
         struct ceph_inode_info *ci;
-        int undo = 0;
         struct ceph_snap_context *snapc;
+        int ret;
 
         if (unlikely(!mapping))
                 return !TestSetPageDirty(page);
 
-        if (TestSetPageDirty(page)) {
+        if (PageDirty(page)) {
                 dout("%p set_page_dirty %p idx %lu -- already dirty\n",
                      mapping->host, page, page->index);
+                BUG_ON(!PagePrivate(page));
                 return 0;
         }
 
@@ -107,35 +108,19 @@ static int ceph_set_page_dirty(struct page *page)
              snapc, snapc->seq, snapc->num_snaps);
         spin_unlock(&ci->i_ceph_lock);
 
-        /* now adjust page */
-        spin_lock_irq(&mapping->tree_lock);
-        if (page->mapping) {    /* Race with truncate? */
-                WARN_ON_ONCE(!PageUptodate(page));
-                account_page_dirtied(page, page->mapping);
-                radix_tree_tag_set(&mapping->page_tree,
-                                page_index(page), PAGECACHE_TAG_DIRTY);
-
-                /*
-                 * Reference snap context in page->private.  Also set
-                 * PagePrivate so that we get invalidatepage callback.
-                 */
-                page->private = (unsigned long)snapc;
-                SetPagePrivate(page);
-        } else {
-                dout("ANON set_page_dirty %p (raced truncate?)\n", page);
-                undo = 1;
-        }
-
-        spin_unlock_irq(&mapping->tree_lock);
-
-        if (undo)
-                /* whoops, we failed to dirty the page */
-                ceph_put_wrbuffer_cap_refs(ci, 1, snapc);
+        /*
+         * Reference snap context in page->private.  Also set
+         * PagePrivate so that we get invalidatepage callback.
+         */
+        BUG_ON(PagePrivate(page));
+        page->private = (unsigned long)snapc;
+        SetPagePrivate(page);
 
-        __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
+        ret = __set_page_dirty_nobuffers(page);
+        WARN_ON(!PageLocked(page));
+        WARN_ON(!page->mapping);
 
-        BUG_ON(!PageDirty(page));
-        return 1;
+        return ret;
 }
 
 /*