NFS: Add a count of the number of unstable writes carried by an inode

In order to know when we should do opportunistic commits of the unstable
writes, when the VM is doing a background flush, we add a field to count
the number of unstable writes.

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

3 files changed, 12 insertions, 4 deletions

diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 89e98312599d..aa5a831001ab 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -1404,6 +1404,7 @@ static void init_once(void *foo)
         INIT_LIST_HEAD(&nfsi->access_cache_inode_lru);
         INIT_RADIX_TREE(&nfsi->nfs_page_tree, GFP_ATOMIC);
         nfsi->npages = 0;
+        nfsi->ncommit = 0;
         atomic_set(&nfsi->silly_count, 1);
         INIT_HLIST_HEAD(&nfsi->silly_list);
         init_waitqueue_head(&nfsi->waitqueue);
diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 09e97097baaa..dc08a6fbde67 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -438,6 +438,7 @@ nfs_mark_request_commit(struct nfs_page *req)
         radix_tree_tag_set(&nfsi->nfs_page_tree,
                         req->wb_index,
                         NFS_PAGE_TAG_COMMIT);
+        nfsi->ncommit++;
         spin_unlock(&inode->i_lock);
         inc_zone_page_state(req->wb_page, NR_UNSTABLE_NFS);
         inc_bdi_stat(req->wb_page->mapping->backing_dev_info, BDI_RECLAIMABLE);
@@ -573,11 +574,15 @@ static int
 nfs_scan_commit(struct inode *inode, struct list_head *dst, pgoff_t idx_start, unsigned int npages)
 {
         struct nfs_inode *nfsi = NFS_I(inode);
+        int ret;
 
         if (!nfs_need_commit(nfsi))
                 return 0;
 
-        return nfs_scan_list(nfsi, dst, idx_start, npages, NFS_PAGE_TAG_COMMIT);
+        ret = nfs_scan_list(nfsi, dst, idx_start, npages, NFS_PAGE_TAG_COMMIT);
+        if (ret > 0)
+                nfsi->ncommit -= ret;
+        return ret;
 }
 #else
 static inline int nfs_need_commit(struct nfs_inode *nfsi)
@@ -642,9 +647,10 @@ static struct nfs_page *nfs_try_to_update_request(struct inode *inode,
                 spin_lock(&inode->i_lock);
         }
 
-        if (nfs_clear_request_commit(req))
-                radix_tree_tag_clear(&NFS_I(inode)->nfs_page_tree,
-                                req->wb_index, NFS_PAGE_TAG_COMMIT);
+        if (nfs_clear_request_commit(req) &&
+                        radix_tree_tag_clear(&NFS_I(inode)->nfs_page_tree,
+                                req->wb_index, NFS_PAGE_TAG_COMMIT) != NULL)
+                NFS_I(inode)->ncommit--;
 
         /* Okay, the request matches. Update the region */
         if (offset < req->wb_offset) {
diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index 384ea3ef2863..309217f46e28 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -166,6 +166,7 @@ struct nfs_inode {
         struct radix_tree_root  nfs_page_tree;
 
         unsigned long           npages;
+        unsigned long           ncommit;
 
         /* Open contexts for shared mmap writes */
         struct list_head        open_files;