[PATCH v4 12/21] tftp: record whether tftp file is opened for lookup operation only

[Enrico Scholz]

Opening a tftp is done in two steps: at first `tftp_lookup()` is
called to get the filesize and then it is opened again and data are
read.

The `tftp_lookup()` call sends only a RRQ/WRQ, reads then the "tsize"
from the response and closes the transfer by sending an error datagram.
The tftp server will send a full data window.

To prevent unneeded traffic, later patches set parameters to reduce
the size of the server response.

We need knowledge about type of operation which is recorded in an
"is_getattr" attribute.

Signed-off-by: Enrico Scholz <enrico.scholz at sigma-chemnitz.de>
---
 fs/tftp.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/fs/tftp.c b/fs/tftp.c
index 4e31adcd60ed..7181c58d1083 100644
--- a/fs/tftp.c
+++ b/fs/tftp.c
@@ -95,6 +95,7 @@ struct file_priv {
 	void *buf;
 	int blocksize;
 	int block_requested;
+	bool is_getattr;
 };
 
 struct tftp_priv {
@@ -460,7 +461,7 @@ static int tftp_start_transfer(struct file_priv *priv)
 }
 
 static struct file_priv *tftp_do_open(struct device_d *dev,
-		int accmode, struct dentry *dentry)
+		int accmode, struct dentry *dentry, bool is_getattr)
 {
 	struct fs_device_d *fsdev = dev_to_fs_device(dev);
 	struct file_priv *priv;
@@ -489,6 +490,7 @@ static struct file_priv *tftp_do_open(struct device_d *dev,
 	priv->filename = dpath(dentry, fsdev->vfsmount.mnt_root);
 	priv->blocksize = TFTP_BLOCK_SIZE;
 	priv->block_requested = -1;
+	priv->is_getattr = is_getattr;
 
 	parseopt_hu(fsdev->options, "port", &port);
 
@@ -567,7 +569,7 @@ static int tftp_open(struct device_d *dev, FILE *file, const char *filename)
 {
 	struct file_priv *priv;
 
-	priv = tftp_do_open(dev, file->flags, file->dentry);
+	priv = tftp_do_open(dev, file->flags, file->dentry, false);
 	if (IS_ERR(priv))
 		return PTR_ERR(priv);
 
@@ -783,7 +785,7 @@ static struct dentry *tftp_lookup(struct inode *dir, struct dentry *dentry,
 	struct file_priv *priv;
 	loff_t filesize;
 
-	priv = tftp_do_open(&fsdev->dev, O_RDONLY, dentry);
+	priv = tftp_do_open(&fsdev->dev, O_RDONLY, dentry, true);
 	if (IS_ERR(priv))
 		return NULL;
 
-- 
2.37.2