[PATCH v5 08/18] 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 the FMODE_CREATED flag that it set.  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.

A subtle difference here is that we now must only pass O_EXCL to
dentry_create() for NFS4_CREATE_GUARDED.  For the EXCLUSIVE create modes
we want a successful open even if the file already exists.  We then
check the verifier after the open succeeded to see if it was exclusive.

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 | 69 ++++++++++++++++++++--------------------------
 2 files changed, 32 insertions(+), 39 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 19ce43c9a6e6..9af1d5bc89fc 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -5077,6 +5077,8 @@ 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 a311810abfde..8840f6dd8a0a 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -211,7 +211,11 @@ nfsd4_vfs_create(struct svc_fh *fhp, struct dentry **child,
 	int oflags;
 
 	oflags = O_CREAT | O_LARGEFILE;
-	if (nfsd4_create_is_exclusive(open->op_createmode))
+	/*
+	 * For the EXCLUSIVE modes we do our own uniqueness tests
+	 * so don't want O_EXCL.
+	 */
+	if (open->op_createmode == NFS4_CREATE_GUARDED)
 		oflags |= O_EXCL;
 
 	switch (open->op_share_access & NFS4_SHARE_ACCESS_BOTH) {
@@ -360,22 +364,30 @@ 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
@@ -383,41 +395,20 @@ 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:
-			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;
-			}
+			open->op_truncate = (d_is_reg(child) &&
+					     (iap->ia_valid & ATTR_SIZE) &&
+					     !iap->ia_size);
+		} else
 			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:
 	status = nfsd_create_setattr(rqstp, fhp, resfhp, &attrs);
 
 	if (attrs.na_labelerr)
-- 
2.50.0.107.gf914562f5916.dirty