fs/9p: Don't use O_TRUNC flag in TOPEN and TLOPEN request

We do the truncate via setattr request, hence don't pass the O_TRUNC flag in
open request. Without this patch we end up sending zero sized write request
to server when we try to truncate. Some servers (VirtFS) were not handling that
properly.
Reported-by: NM. Mohan Kumar <mohan@in.ibm.com>
Signed-off-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: NEric Van Hensbergen <ericvh@gmail.com>

fs/9p/vfs_file.c

@@ -80,10 +80,6 @@ int v9fs_file_open(struct inode *inode, struct file *file)
 			p9_client_clunk(fid);
 			return err;
 		}
-		if (file->f_flags & O_TRUNC) {
-			i_size_write(inode, 0);
-			inode->i_blocks = 0;
-		}
 		if ((file->f_flags & O_APPEND) &&
 			(!v9fs_proto_dotu(v9ses) && !v9fs_proto_dotl(v9ses)))
 			generic_file_llseek(file, 0, SEEK_END);

fs/9p/vfs_inode.c

@@ -192,9 +192,6 @@ int v9fs_uflags2omode(int uflags, int extended)
 		break;
 	}
 
-	if (uflags & O_TRUNC)
-		ret |= P9_OTRUNC;
-
 	if (extended) {
 		if (uflags & O_EXCL)
 			ret |= P9_OEXCL;

fs/9p/vfs_inode_dotl.c

@@ -186,7 +186,6 @@ static int v9fs_mapped_dotl_flags(int flags)
 		{ O_CREAT,	P9_DOTL_CREATE },
 		{ O_EXCL,	P9_DOTL_EXCL },
 		{ O_NOCTTY,	P9_DOTL_NOCTTY },
-		{ O_TRUNC,	P9_DOTL_TRUNC },
 		{ O_APPEND,	P9_DOTL_APPEND },
 		{ O_NONBLOCK,	P9_DOTL_NONBLOCK },
 		{ O_DSYNC,	P9_DOTL_DSYNC },