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>

1 files changed, 30 insertions, 12 deletions

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index a06167e20b72..8d8fa6d4cfcc 100644
--- 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;
 }