[PATCH 5/7] nfsd: switch NFS4 OPEN to use vfs_lookup_open()

[NeilBrown <neilb@ownmail.net>]

From: NeilBrown <neil@brown.name>

The functionality that was recently gathered into do_lookup_open() is
now available from the vfs as vfs_lookup_open().  So nfsd4_create_file()
can call that, with a few adjustments.

This implementation shares more code with syscall open paths and so uses
some filesystem interfaces slightly more correctly.  It also takes the
responsibility for locking out of nfsd so that planned changes can
happen entirely in VFS code.

We need to pass O_NONBLOCK so that that EWOULDBLOCK errors from
break_lease of try_break_deleg() get passed back.

We need to mask any type out of "mode" else vfs_lookup_open() will warn.

vfs_lookup_open() always returns -EFTYPE if a non-regular-file was
found, and provides the dentry in parent.dentry.  We can use
nfsd_check_obj_is_reg() to turn this into an error.

As parent.dentry could be NULL, we enhance nfsd_check_obj_is_reg() to
cope with that.

vfs_lookup_open() will return -EEXIST if required for
NFS_CREATE_GUARDED4 as O_EXCL is passed in.  Other checks for
and existing object need only test for nfsd4_create_is_exclusive().
Make both these tests (for non-regular and for regular) the same.

Signed-off-by: NeilBrown <neil@brown.name>
---
 fs/nfsd/nfs4proc.c | 83 ++++++++++++----------------------------------
 1 file changed, 21 insertions(+), 62 deletions(-)

diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index 3a82af381a8d..0fd5a6411ed3 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -225,8 +225,11 @@ do_open_permission(struct svc_rqst *rqstp, struct svc_fh *current_fh, struct nfs
 
 static int nfsd_check_obj_isreg(struct dentry *child)
 {
-	umode_t mode = d_inode(child)->i_mode;
+	umode_t mode;
 
+	if (!child || !d_inode(child))
+		return -EFTYPE;
+	mode = d_inode(child)->i_mode;
 	if (S_ISREG(mode))
 		return 0;
 	if (S_ISDIR(mode))
@@ -250,52 +253,6 @@ static inline bool nfsd4_create_is_exclusive(int createmode)
 		createmode == NFS4_CREATE_EXCLUSIVE4_1;
 }
 
-static struct file *do_lookup_open(struct path *parent,
-				   struct qstr *name,
-				   unsigned int oflags,
-				   umode_t mode)
-{
-	struct file *filp = NULL;
-	struct path path;
-	struct dentry *child;
-	int want_write_err = 0;
-
-	want_write_err = mnt_want_write(parent->mnt);
-
-	child = start_creating(&nop_mnt_idmap, parent->dentry, name);
-	if (IS_ERR(child)) {
-		filp = ERR_CAST(child);
-		goto out;
-	}
-	path.mnt = parent->mnt;
-	path.dentry = child;
-
-	if (d_really_is_positive(child)) {
-		/*
-		 * open the file so that we consistently have a valid
-		 * op_filp and consequently a valid ->f_path.dentry.
-		 */
-		int err = nfsd_check_obj_isreg(child);
-
-		if (err)
-			filp = ERR_PTR(err);
-		else
-			filp = dentry_open(&path, oflags, current_cred());
-	} else if (!(oflags & O_CREAT)) {
-		filp = ERR_PTR(-ENOENT);
-	} else if (want_write_err) {
-		filp = ERR_PTR(want_write_err);
-	} else {
-		filp = dentry_create(&path, oflags, mode, current_cred());
-		child = path.dentry;
-	}
-	end_creating(child);
-out:
-	if (!want_write_err)
-		mnt_drop_write(parent->mnt);
-	return filp;
-}
-
 /*
  * Implement NFSv4's unchecked, guarded, and exclusive create
  * semantics for regular files. Open state for this new file is
@@ -312,7 +269,7 @@ nfsd4_create_file(struct svc_rqst *rqstp, struct svc_fh *fhp,
 		.na_iattr	= iap,
 		.na_seclabel	= &open->op_label,
 	};
-	int oflags = O_CREAT | O_LARGEFILE;
+	int oflags = O_CREAT | O_LARGEFILE | O_NONBLOCK;
 	struct dentry *child = ERR_PTR(-EINVAL);
 	struct path parent = {
 		.mnt = fhp->fh_export->ex_path.mnt,
@@ -424,28 +381,29 @@ nfsd4_create_file(struct svc_rqst *rqstp, struct svc_fh *fhp,
 		/* Might still succeed if no create is needed */
 		oflags &= ~O_CREAT;
 
-	open->op_filp = do_lookup_open(&parent,
-				       &QSTR_LEN(open->op_fname,
-						 open->op_fnamelen),
-				       oflags,
-				       open->op_iattr.ia_mode);
+	dget(parent.dentry);
+	open->op_filp = vfs_lookup_open(&parent,
+					&QSTR_LEN(open->op_fname,
+						  open->op_fnamelen),
+					oflags,
+					open->op_iattr.ia_mode & S_IALLUGO);
 	if (IS_ERR(open->op_filp)) {
 		int hosterr = PTR_ERR(open->op_filp);
 
-		if (open->op_createmode != NFS4_CREATE_UNCHECKED) {
-			switch (hosterr) {
-			case -EISDIR:
-			case -ELOOP:
-			case -EFTYPE:
+		if (hosterr == -EFTYPE) {
+			if (nfsd4_create_is_exclusive(open->op_createmode))
 				hosterr = -EEXIST;
-			}
+			else
+				hosterr = nfsd_check_obj_isreg(parent.dentry);
 		}
 		status = nfserrno(hosterr);
 		open->op_filp = NULL;
 		if (status == nfserr_noent && create_status)
 			status = create_status;
+		dput(parent.dentry);
 		goto out;
 	}
+	dput(parent.dentry);
 
 	child = open->op_filp->f_path.dentry;
 	open->op_created = open->op_filp->f_mode & FMODE_CREATED;
@@ -462,7 +420,9 @@ nfsd4_create_file(struct svc_rqst *rqstp, struct svc_fh *fhp,
 		open->op_created = true;
 
 	if (!open->op_created) {
-		if (open->op_createmode == NFS4_CREATE_UNCHECKED) {
+		if (nfsd4_create_is_exclusive(open->op_createmode)) {
+			status = nfserr_exist;
+		} else {
 			/* NFSv4 protocol requires change attributes
 			 * even though no change happened.
 			 */
@@ -477,8 +437,7 @@ nfsd4_create_file(struct svc_rqst *rqstp, struct svc_fh *fhp,
 			open->op_truncate = (d_is_reg(child) &&
 					     (iap->ia_valid & ATTR_SIZE) &&
 					     !iap->ia_size);
-		} else
-			status = nfserr_exist;
+		}
 		goto out;
 	}
 	/* file was created */
-- 
2.50.0.107.gf914562f5916.dirty