[PATCH 05/10] nfsd: in nfsd4_create_file() let VFS report if file was created.

From: NeilBrown <neil-+NVA1uvv1dVBDLzU/[email protected]>

nfsd4_create_file() currently assumes that if a lookup failed but then a
create succeeds, then the "create" operation actually created the file.
With atomic_open this may not be the case - some other actor might have
created the file between the lookup and the create.

So we move the call to nfsd4_vfs_create() earlier and set ->op_created
based on that.  Then use "!  ->op_created" to trigger nfserr_exist
handling.

The switch statement is split up into two if() statements.
First we check for the possibility of a successful exclusive
create and set ->op_create to true if appropriate.
Then we check for NFS4_CREATE_UNCHECKED to decide if a
pre-existing file means an error or success.

This allows us to combine the two fh_compose() calls to one place.

Also move the clearing of ATTR_SIZE for a newly created file down to a
point where we know we have actually created the file.

With this rearrangement we now repeat the setattr when an exclusive
create is repeated.  This should be both rare and harmless, and it
simplifies the code.

The above requires changing dentry_create() to reliably set
FMODE_CREATED when the file was actually created.  Previously it only
sets this flag when atomic_open is used.

Signed-off-by: NeilBrown <neil-+NVA1uvv1dVBDLzU/[email protected]>
---
 fs/namei.c         |  2 ++
 fs/nfsd/nfs4proc.c | 63 ++++++++++++++++++----------------------------
 2 files changed, 27 insertions(+), 38 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 5cc9f0f466b8..e0a62198fc60 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -5073,6 +5073,8 @@ struct file *dentry_create(struct path *path, int flags, umode_t mode,
 		error = vfs_create(mnt_idmap(path->mnt), path->dentry, mode, NULL);
 		if (!error)
 			error = vfs_open(path, file);
+		if (!error)
+			file->f_mode |= FMODE_CREATED;
 	}
 	if (unlikely(error))
 		return ERR_PTR(error);
diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index 5b7f0314776f..cbb549ca6567 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -333,22 +333,30 @@ nfsd4_create_file(struct svc_rqst *rqstp, struct svc_fh *fhp,
 		status = fh_verify(rqstp, fhp, S_IFDIR, NFSD_MAY_CREATE);
 		if (status != nfs_ok)
 			goto out;
-	}
-
-	if (d_really_is_positive(child)) {
-		/* NFSv4 protocol requires change attributes even though
-		 * no change happened.
-		 */
-		fh_fill_post_noop(fhp);
 
-		status = fh_compose(resfhp, fhp->fh_export, child, fhp);
+		status = nfsd4_vfs_create(fhp, &child, open);
 		if (status != nfs_ok)
 			goto out;
+		open->op_created = open->op_filp->f_mode & FMODE_CREATED;
+	}
 
-		switch (open->op_createmode) {
-		case NFS4_CREATE_UNCHECKED:
-			if (!d_is_reg(child))
-				break;
+	status = fh_compose(resfhp, fhp->fh_export, child, fhp);
+	if (status != nfs_ok)
+		goto out;
+
+	if (!open->op_created &&
+	    nfsd4_create_is_exclusive(open->op_createmode) &&
+	    inode_get_mtime_sec(d_inode(child)) == v_mtime &&
+	    inode_get_atime_sec(d_inode(child)) == v_atime &&
+	    d_inode(child)->i_size == 0)
+		open->op_created = true;
+
+	if (!open->op_created) {
+		if (open->op_createmode == NFS4_CREATE_UNCHECKED) {
+			/* NFSv4 protocol requires change attributes
+			 * even though no change happened.
+			 */
+			fh_fill_post_noop(fhp);
 
 			/*
 			 * In NFSv4, we don't want to truncate the file
@@ -356,41 +364,20 @@ nfsd4_create_file(struct svc_rqst *rqstp, struct svc_fh *fhp,
 			 * some other reason. Furthermore, if the size is
 			 * nonzero, we should ignore it according to spec!
 			 */
-			open->op_truncate = (iap->ia_valid & ATTR_SIZE) &&
-						!iap->ia_size;
-			break;
-		case NFS4_CREATE_GUARDED:
+			open->op_truncate = (d_is_reg(child) &&
+					     (iap->ia_valid & ATTR_SIZE) &&
+					     !iap->ia_size);
+		} else
 			status = nfserr_exist;
-			break;
-		case NFS4_CREATE_EXCLUSIVE:
-		case NFS4_CREATE_EXCLUSIVE4_1:
-			if (inode_get_mtime_sec(d_inode(child)) == v_mtime &&
-			    inode_get_atime_sec(d_inode(child)) == v_atime &&
-			    d_inode(child)->i_size == 0) {
-				open->op_created = true;
-				goto set_attr;
-			}
-			status = nfserr_exist;
-			break;
-		}
 		goto out;
 	}
-
-	status = nfsd4_vfs_create(fhp, &child, open);
-	if (status != nfs_ok)
-		goto out;
-	open->op_created = true;
+	/* file was created */
 	fh_fill_post_attrs(fhp);
 
-	status = fh_compose(resfhp, fhp->fh_export, child, fhp);
-	if (status != nfs_ok)
-		goto out;
-
 	/* A newly created file already has a file size of zero. */
 	if ((iap->ia_valid & ATTR_SIZE) && (iap->ia_size == 0))
 		iap->ia_valid &= ~ATTR_SIZE;
 
-set_attr:
 	if (is_create_with_attrs(open)) {
 		status = nfsd_create_setattr(rqstp, fhp, resfhp, &attrs);
 
-- 
2.50.0.107.gf914562f5916.dirty