Merge tag 'nfs-for-6.17-2' of git://git.linux-nfs.org/projects/trondmy/linux-nfs

Pull NFS client fix from Trond Myklebust:

 - NFS: Fix a data corrupting race when updating an existing write

* tag 'nfs-for-6.17-2' of git://git.linux-nfs.org/projects/trondmy/linux-nfs:
  NFS: Fix a race when updating an existing write

1 files changed, 10 insertions, 19 deletions

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index fa5c41d0989a..8b7c04737967 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -153,20 +153,10 @@ nfs_page_set_inode_ref(struct nfs_page *req, struct inode *inode)
 	}
 }
 
-static int
-nfs_cancel_remove_inode(struct nfs_page *req, struct inode *inode)
+static void nfs_cancel_remove_inode(struct nfs_page *req, struct inode *inode)
 {
-	int ret;
-
-	if (!test_bit(PG_REMOVE, &req->wb_flags))
-		return 0;
-	ret = nfs_page_group_lock(req);
-	if (ret)
-		return ret;
 	if (test_and_clear_bit(PG_REMOVE, &req->wb_flags))
 		nfs_page_set_inode_ref(req, inode);
-	nfs_page_group_unlock(req);
-	return 0;
 }
 
 /**
@@ -585,19 +575,18 @@ retry:
 		}
 	}
 
+	ret = nfs_page_group_lock(head);
+	if (ret < 0)
+		goto out_unlock;
+
 	/* Ensure that nobody removed the request before we locked it */
 	if (head != folio->private) {
+		nfs_page_group_unlock(head);
 		nfs_unlock_and_release_request(head);
 		goto retry;
 	}
 
-	ret = nfs_cancel_remove_inode(head, inode);
-	if (ret < 0)
-		goto out_unlock;
-
-	ret = nfs_page_group_lock(head);
-	if (ret < 0)
-		goto out_unlock;
+	nfs_cancel_remove_inode(head, inode);
 
 	/* lock each request in the page group */
 	for (subreq = head->wb_this_page;
@@ -786,7 +775,8 @@ static void nfs_inode_remove_request(struct nfs_page *req)
 {
 	struct nfs_inode *nfsi = NFS_I(nfs_page_to_inode(req));
 
-	if (nfs_page_group_sync_on_bit(req, PG_REMOVE)) {
+	nfs_page_group_lock(req);
+	if (nfs_page_group_sync_on_bit_locked(req, PG_REMOVE)) {
 		struct folio *folio = nfs_page_to_folio(req->wb_head);
 		struct address_space *mapping = folio->mapping;
 
@@ -798,6 +788,7 @@ static void nfs_inode_remove_request(struct nfs_page *req)
 		}
 		spin_unlock(&mapping->i_private_lock);
 	}
+	nfs_page_group_unlock(req);
 
 	if (test_and_clear_bit(PG_INODE_REF, &req->wb_flags)) {
 		atomic_long_dec(&nfsi->nrequests);