Enable packetized mode for autofs v5+ only

In commit 64f371bc3107e69efce563a3d0f0e6880de0d537 "autofs: make the
autofsv5 packet file descriptor use a packetized pipe", we enable
the packetized mode of the pipe unconditionally for all versions
of autofs protocol, but we actually only tested v5 version, and
it is unknown how it worked for previous versions of the protocol
and older binaries, who may actually read the packed piece by piece.
Enable the packetized mode only if client protocol is >= 5.

Note: the current function autofs_prepare_pipe() is called from 2
places which does the same thing with other fields of sbi structure,
so all this work may be put into a common function.

Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>


diff --git a/fs/autofs4/autofs_i.h b/fs/autofs4/autofs_i.h
index 908e184..72e315a 100644
--- a/fs/autofs4/autofs_i.h
+++ b/fs/autofs4/autofs_i.h
@@ -269,14 +269,17 @@ int autofs4_fill_super(struct super_block *, void *, int);
 struct autofs_info *autofs4_new_ino(struct autofs_sb_info *);
 void autofs4_clean_ino(struct autofs_info *);
 
-static inline int autofs_prepare_pipe(struct file *pipe)
+static inline int autofs_prepare_pipe(struct autofs_sb_info *sbi,
+				       struct file *pipe)
 {
 	if (!pipe->f_op || !pipe->f_op->write)
 		return -EINVAL;
 	if (!S_ISFIFO(pipe->f_dentry->d_inode->i_mode))
 		return -EINVAL;
-	/* We want a packet pipe */
-	pipe->f_flags |= O_DIRECT;
+	if (sbi->version >= 5)
+		/* We want a packet pipe */
+		pipe->f_flags |= O_DIRECT;
+	sbi->pipe = pipe;
 	return 0;
 }
 
diff --git a/fs/autofs4/dev-ioctl.c b/fs/autofs4/dev-ioctl.c
index aa9103f..cdf9dbc 100644
--- a/fs/autofs4/dev-ioctl.c
+++ b/fs/autofs4/dev-ioctl.c
@@ -376,14 +376,13 @@ static int autofs_dev_ioctl_setpipefd(struct file *fp,
 			err = -EBADF;
 			goto out;
 		}
-		if (autofs_prepare_pipe(pipe) < 0) {
+		if (autofs_prepare_pipe(sbi, pipe) < 0) {
 			err = -EPIPE;
 			fput(pipe);
 			goto out;
 		}
 		sbi->oz_pgrp = task_pgrp_nr(current);
 		sbi->pipefd = pipefd;
-		sbi->pipe = pipe;
 		sbi->catatonic = 0;
 	}
 out:
diff --git a/fs/autofs4/inode.c b/fs/autofs4/inode.c
index 6e488eb..3b1eb5c 100644
--- a/fs/autofs4/inode.c
+++ b/fs/autofs4/inode.c
@@ -290,9 +290,8 @@ int autofs4_fill_super(struct super_block *s, void *data, int silent)
 		printk("autofs: could not open pipe file descriptor\n");
 		goto fail_dput;
 	}
-	if (autofs_prepare_pipe(pipe) < 0)
+	if (autofs_prepare_pipe(sbi, pipe) < 0)
 		goto fail_fput;
-	sbi->pipe = pipe;
 	sbi->pipefd = pipefd;
 	sbi->catatonic = 0;