cifs: improve symlink handling for smb2+

When creating inode for symlink, the client used to send below
requests to fill it in:

    * create+query_info+close (STATUS_STOPPED_ON_SYMLINK)
    * create(+reparse_flag)+query_info+close (set file attrs)
    * create+ioctl(get_reparse)+close (query reparse tag)

and then for every access to the symlink dentry, the ->link() method
would send another:

    * create+ioctl(get_reparse)+close (parse symlink)

So, in order to improve:

    (i) Get rid of unnecessary roundtrips and then resolve symlinks as
	follows:

        * create+query_info+close (STATUS_STOPPED_ON_SYMLINK +
	                           parse symlink + get reparse tag)
        * create(+reparse_flag)+query_info+close (set file attrs)

    (ii) Set the resolved symlink target directly in inode->i_link and
         use simple_get_link() for ->link() to simply return it.

Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

1 files changed, 22 insertions, 19 deletions

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 7d756721e1a6..dcec1690312b 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -209,16 +209,14 @@ posix_open_ret:
 }
 #endif /* CONFIG_CIFS_ALLOW_INSECURE_LEGACY */
 
-static int
-cifs_nt_open(const char *full_path, struct inode *inode, struct cifs_sb_info *cifs_sb,
-	     struct cifs_tcon *tcon, unsigned int f_flags, __u32 *oplock,
-	     struct cifs_fid *fid, unsigned int xid)
+static int cifs_nt_open(const char *full_path, struct inode *inode, struct cifs_sb_info *cifs_sb,
+			struct cifs_tcon *tcon, unsigned int f_flags, __u32 *oplock,
+			struct cifs_fid *fid, unsigned int xid, struct cifs_open_info_data *buf)
 {
 	int rc;
 	int desired_access;
 	int disposition;
 	int create_options = CREATE_NOT_DIR;
-	FILE_ALL_INFO *buf;
 	struct TCP_Server_Info *server = tcon->ses->server;
 	struct cifs_open_parms oparms;
 
@@ -255,10 +253,6 @@ cifs_nt_open(const char *full_path, struct inode *inode, struct cifs_sb_info *ci
 
 	/* BB pass O_SYNC flag through on file attributes .. BB */
 
-	buf = kmalloc(sizeof(FILE_ALL_INFO), GFP_KERNEL);
-	if (!buf)
-		return -ENOMEM;
-
 	/* O_SYNC also has bit for O_DSYNC so following check picks up either */
 	if (f_flags & O_SYNC)
 		create_options |= CREATE_WRITE_THROUGH;
@@ -276,9 +270,8 @@ cifs_nt_open(const char *full_path, struct inode *inode, struct cifs_sb_info *ci
 	oparms.reconnect = false;
 
 	rc = server->ops->open(xid, &oparms, oplock, buf);
-
 	if (rc)
-		goto out;
+		return rc;
 
 	/* TODO: Add support for calling posix query info but with passing in fid */
 	if (tcon->unix_ext)
@@ -294,8 +287,6 @@ cifs_nt_open(const char *full_path, struct inode *inode, struct cifs_sb_info *ci
 			rc = -EOPENSTALE;
 	}
 
-out:
-	kfree(buf);
 	return rc;
 }
 
@@ -325,9 +316,9 @@ cifs_down_write(struct rw_semaphore *sem)
 
 static void cifsFileInfo_put_work(struct work_struct *work);
 
-struct cifsFileInfo *
-cifs_new_fileinfo(struct cifs_fid *fid, struct file *file,
-		  struct tcon_link *tlink, __u32 oplock)
+struct cifsFileInfo *cifs_new_fileinfo(struct cifs_fid *fid, struct file *file,
+				       struct tcon_link *tlink, __u32 oplock,
+				       const char *symlink_target)
 {
 	struct dentry *dentry = file_dentry(file);
 	struct inode *inode = d_inode(dentry);
@@ -347,6 +338,15 @@ cifs_new_fileinfo(struct cifs_fid *fid, struct file *file,
 		return NULL;
 	}
 
+	if (symlink_target) {
+		cfile->symlink_target = kstrdup(symlink_target, GFP_KERNEL);
+		if (!cfile->symlink_target) {
+			kfree(fdlocks);
+			kfree(cfile);
+			return NULL;
+		}
+	}
+
 	INIT_LIST_HEAD(&fdlocks->locks);
 	fdlocks->cfile = cfile;
 	cfile->llist = fdlocks;
@@ -440,6 +440,7 @@ static void cifsFileInfo_put_final(struct cifsFileInfo *cifs_file)
 	cifs_put_tlink(cifs_file->tlink);
 	dput(cifs_file->dentry);
 	cifs_sb_deactive(sb);
+	kfree(cifs_file->symlink_target);
 	kfree(cifs_file);
 }
 
@@ -572,6 +573,7 @@ int cifs_open(struct inode *inode, struct file *file)
 	bool posix_open_ok = false;
 	struct cifs_fid fid;
 	struct cifs_pending_open open;
+	struct cifs_open_info_data data = {};
 
 	xid = get_xid();
 
@@ -662,15 +664,15 @@ int cifs_open(struct inode *inode, struct file *file)
 		if (server->ops->get_lease_key)
 			server->ops->get_lease_key(inode, &fid);
 
-		rc = cifs_nt_open(full_path, inode, cifs_sb, tcon,
-				  file->f_flags, &oplock, &fid, xid);
+		rc = cifs_nt_open(full_path, inode, cifs_sb, tcon, file->f_flags, &oplock, &fid,
+				  xid, &data);
 		if (rc) {
 			cifs_del_pending_open(&open);
 			goto out;
 		}
 	}
 
-	cfile = cifs_new_fileinfo(&fid, file, tlink, oplock);
+	cfile = cifs_new_fileinfo(&fid, file, tlink, oplock, data.symlink_target);
 	if (cfile == NULL) {
 		if (server->ops->close)
 			server->ops->close(xid, tcon, &fid);
@@ -712,6 +714,7 @@ out:
 	free_dentry_path(page);
 	free_xid(xid);
 	cifs_put_tlink(tlink);
+	cifs_free_open_info(&data);
 	return rc;
 }