NFSv4: Convert nfs_lock_and_join_requests() to use nfs_page_find_head_request()

Hide the locking from nfs_lock_and_join_requests() so that we can
separate out the requirements for swapcache pages.

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

1 files changed, 20 insertions, 15 deletions

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 759e37d26acf..a06167e20b72 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -154,6 +154,14 @@ static void nfs_context_set_write_error(struct nfs_open_context *ctx, int error)
         set_bit(NFS_CONTEXT_ERROR_WRITE, &ctx->flags);
 }
 
+static struct nfs_page *
+nfs_page_private_request(struct page *page)
+{
+        if (!PagePrivate(page))
+                return NULL;
+        return (struct nfs_page *)page_private(page);
+}
+
 /*
  * nfs_page_find_head_request_locked - find head request associated with @page
  *
@@ -164,11 +172,10 @@ static void nfs_context_set_write_error(struct nfs_open_context *ctx, int error)
 static struct nfs_page *
 nfs_page_find_head_request_locked(struct nfs_inode *nfsi, struct page *page)
 {
-        struct nfs_page *req = NULL;
+        struct nfs_page *req;
 
-        if (PagePrivate(page))
-                req = (struct nfs_page *)page_private(page);
-        else if (unlikely(PageSwapCache(page)))
+        req = nfs_page_private_request(page);
+        if (!req && unlikely(PageSwapCache(page)))
                 req = nfs_page_search_commits_for_head_request_locked(nfsi,
                         page);
 
@@ -448,31 +455,29 @@ nfs_lock_and_join_requests(struct page *page)
         int ret;
 
 try_again:
-        if (!(PagePrivate(page) || PageSwapCache(page)))
-                return NULL;
-        spin_lock(&inode->i_lock);
         /*
          * A reference is taken only on the head request which acts as a
          * reference to the whole page group - the group will not be destroyed
          * until the head reference is released.
          */
-        head = nfs_page_find_head_request_locked(NFS_I(inode), page);
-
-        if (!head) {
-                spin_unlock(&inode->i_lock);
+        head = nfs_page_find_head_request(page);
+        if (!head)
                 return NULL;
-        }
 
         /* lock the page head first in order to avoid an ABBA inefficiency */
         if (!nfs_lock_request(head)) {
-                spin_unlock(&inode->i_lock);
                 ret = nfs_wait_on_request(head);
                 nfs_release_request(head);
                 if (ret < 0)
                         return ERR_PTR(ret);
                 goto try_again;
         }
-        spin_unlock(&inode->i_lock);
+
+        /* Ensure that nobody removed the request before we locked it */
+        if (head != nfs_page_private_request(page) && !PageSwapCache(page)) {
+                nfs_unlock_and_release_request(head);
+                goto try_again;
+        }
 
         ret = nfs_page_group_lock(head);
         if (ret < 0) {
@@ -559,7 +564,7 @@ try_again:
                 return NULL;
         }
 
-        /* still holds ref on head from nfs_page_find_head_request_locked
+        /* still holds ref on head from nfs_page_find_head_request
          * and still has lock on head from lock loop */
         return head;
 }