NFS: Refactor nfs_page_find_head_request()

Split out the 2 cases so that we can treat the locking differently.
The issue is that the locking in the pageswapcache cache is highly
linked to the commit list locking.

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

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index a06167e..8d8fa6d 100644 (file)
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -170,20 +170,41 @@ nfs_page_private_request(struct page *page)
  * returns matching head request with reference held, or NULL if not found.
  */
 static struct nfs_page *
-nfs_page_find_head_request_locked(struct nfs_inode *nfsi, struct page *page)
+nfs_page_find_private_request(struct page *page)
 {
+       struct inode *inode = page_file_mapping(page)->host;
        struct nfs_page *req;
 
+       if (!PagePrivate(page))
+               return NULL;
+       spin_lock(&inode->i_lock);
        req = nfs_page_private_request(page);
-       if (!req && unlikely(PageSwapCache(page)))
-               req = nfs_page_search_commits_for_head_request_locked(nfsi,
-                       page);
-
        if (req) {
                WARN_ON_ONCE(req->wb_head != req);
                kref_get(&req->wb_kref);
        }
+       spin_unlock(&inode->i_lock);
+       return req;
+}
 
+static struct nfs_page *
+nfs_page_find_swap_request(struct page *page)
+{
+       struct inode *inode = page_file_mapping(page)->host;
+       struct nfs_inode *nfsi = NFS_I(inode);
+       struct nfs_page *req = NULL;
+       if (!PageSwapCache(page))
+               return NULL;
+       spin_lock(&inode->i_lock);
+       if (PageSwapCache(page)) {
+               req = nfs_page_search_commits_for_head_request_locked(nfsi,
+                       page);
+               if (req) {
+                       WARN_ON_ONCE(req->wb_head != req);
+                       kref_get(&req->wb_kref);
+               }
+       }
+       spin_unlock(&inode->i_lock);
        return req;
 }
 
@@ -194,14 +215,11 @@ nfs_page_find_head_request_locked(struct nfs_inode *nfsi, struct page *page)
  */
 static struct nfs_page *nfs_page_find_head_request(struct page *page)
 {
-       struct inode *inode = page_file_mapping(page)->host;
-       struct nfs_page *req = NULL;
+       struct nfs_page *req;
 
-       if (PagePrivate(page) || PageSwapCache(page)) {
-               spin_lock(&inode->i_lock);
-               req = nfs_page_find_head_request_locked(NFS_I(inode), page);
-               spin_unlock(&inode->i_lock);
-       }
+       req = nfs_page_find_private_request(page);
+       if (!req)
+               req = nfs_page_find_swap_request(page);
        return req;
 }