[PATCH 7/8] smb: client: reduce stack usage in smb2_query_symlink()

[Paulo Alcantara <pc@xxxxxxxxxxxxx>]

Clang warns about exceeded stack frame size

  fs/smb/client/smb2ops.c:2974:1: warning: stack frame size (1368)
  exceeds limit (1024) in 'smb2_query_symlink' [-Wframe-larger-than]

Fix this by allocating a qs_vars structure that will hold most of the
large structures.

Signed-off-by: Paulo Alcantara (SUSE) <pc@xxxxxxxxxxxxx>
---
 fs/smb/client/smb2ops.c | 43 ++++++++++++++++++++++++++---------------
 1 file changed, 27 insertions(+), 16 deletions(-)

diff --git a/fs/smb/client/smb2ops.c b/fs/smb/client/smb2ops.c
index d6a15d5ec4d2..9136c77cd407 100644
--- a/fs/smb/client/smb2ops.c
+++ b/fs/smb/client/smb2ops.c
@@ -2970,6 +2970,14 @@ parse_reparse_point(struct reparse_data_buffer *buf,
 	}
 }
 
+struct qs_vars {
+	struct smb_rqst rqst[3];
+	struct kvec rsp_iov[3];
+	struct kvec open_iov[SMB2_CREATE_IOV_SIZE];
+	struct kvec io_iov[SMB2_IOCTL_IOV_SIZE];
+	struct kvec close_iov;
+};
+
 static int
 smb2_query_symlink(const unsigned int xid, struct cifs_tcon *tcon,
 		   struct cifs_sb_info *cifs_sb, const char *full_path,
@@ -2979,16 +2987,14 @@ smb2_query_symlink(const unsigned int xid, struct cifs_tcon *tcon,
 	__le16 *utf16_path = NULL;
 	__u8 oplock = SMB2_OPLOCK_LEVEL_NONE;
 	struct cifs_open_parms oparms;
+	struct smb_rqst *rqst;
 	struct cifs_fid fid;
+	struct qs_vars *vars;
 	struct kvec err_iov = {NULL, 0};
+	struct kvec *rsp_iov;
 	struct TCP_Server_Info *server = cifs_pick_channel(tcon->ses);
 	int flags = CIFS_CP_CREATE_CLOSE_OP;
-	struct smb_rqst rqst[3];
 	int resp_buftype[3];
-	struct kvec rsp_iov[3];
-	struct kvec open_iov[SMB2_CREATE_IOV_SIZE];
-	struct kvec io_iov[SMB2_IOCTL_IOV_SIZE];
-	struct kvec close_iov[1];
 	struct smb2_create_rsp *create_rsp;
 	struct smb2_ioctl_rsp *ioctl_rsp;
 	struct reparse_data_buffer *reparse_buf;
@@ -3002,17 +3008,22 @@ smb2_query_symlink(const unsigned int xid, struct cifs_tcon *tcon,
 	if (smb3_encryption_required(tcon))
 		flags |= CIFS_TRANSFORM_REQ;
 
-	memset(rqst, 0, sizeof(rqst));
-	resp_buftype[0] = resp_buftype[1] = resp_buftype[2] = CIFS_NO_BUFFER;
-	memset(rsp_iov, 0, sizeof(rsp_iov));
-
 	utf16_path = cifs_convert_path_to_utf16(full_path, cifs_sb);
 	if (!utf16_path)
 		return -ENOMEM;
 
+	resp_buftype[0] = resp_buftype[1] = resp_buftype[2] = CIFS_NO_BUFFER;
+
+	vars = kzalloc(sizeof(*vars), GFP_KERNEL);
+	if (!vars) {
+		rc = -ENOMEM;
+		goto out_free_path;
+	}
+	rqst = vars->rqst;
+	rsp_iov = vars->rsp_iov;
+
 	/* Open */
-	memset(&open_iov, 0, sizeof(open_iov));
-	rqst[0].rq_iov = open_iov;
+	rqst[0].rq_iov = vars->open_iov;
 	rqst[0].rq_nvec = SMB2_CREATE_IOV_SIZE;
 
 	oparms = (struct cifs_open_parms) {
@@ -3032,8 +3043,7 @@ smb2_query_symlink(const unsigned int xid, struct cifs_tcon *tcon,
 
 
 	/* IOCTL */
-	memset(&io_iov, 0, sizeof(io_iov));
-	rqst[1].rq_iov = io_iov;
+	rqst[1].rq_iov = vars->io_iov;
 	rqst[1].rq_nvec = SMB2_IOCTL_IOV_SIZE;
 
 	rc = SMB2_ioctl_init(tcon, server,
@@ -3050,8 +3060,7 @@ smb2_query_symlink(const unsigned int xid, struct cifs_tcon *tcon,
 
 
 	/* Close */
-	memset(&close_iov, 0, sizeof(close_iov));
-	rqst[2].rq_iov = close_iov;
+	rqst[2].rq_iov = &vars->close_iov;
 	rqst[2].rq_nvec = 1;
 
 	rc = SMB2_close_init(tcon, server,
@@ -3103,13 +3112,15 @@ smb2_query_symlink(const unsigned int xid, struct cifs_tcon *tcon,
 
  querty_exit:
 	cifs_dbg(FYI, "query symlink rc %d\n", rc);
-	kfree(utf16_path);
 	SMB2_open_free(&rqst[0]);
 	SMB2_ioctl_free(&rqst[1]);
 	SMB2_close_free(&rqst[2]);
 	free_rsp_buf(resp_buftype[0], rsp_iov[0].iov_base);
 	free_rsp_buf(resp_buftype[1], rsp_iov[1].iov_base);
 	free_rsp_buf(resp_buftype[2], rsp_iov[2].iov_base);
+	kfree(vars);
+out_free_path:
+	kfree(utf16_path);
 	return rc;
 }
 
-- 
2.41.0