Re: 2.4 bug: fifo-write causes diskwrites to read-only fs !

[Stephen C. Tweedie (sct@redhat.com)]

Hi,

On Wed, May 28, 2003 at 10:52:30PM +0200, Rob van Nieuwkerk wrote:

> I don't have the POSIX spec, but maybe it specifies what "read-only"
> is supposed to mean somewhere too ..

SingleUnix says:

http://www.opengroup.org/onlinepubs/007904975/basedefs/xbd_chap04.html#tag_04_07

"Marks for update, and updates themselves, are not done for files on
read-only file systems"

So we're wrong here.  Patch below fixes it for me for 2.4.

Cheers,
 Stephen
--- linux-2.4-odirect/fs/inode.c.=K0004=.orig
+++ linux-2.4-odirect/fs/inode.c
@@ -1194,6 +1194,24 @@ void update_atime (struct inode *inode)
 	mark_inode_dirty_sync (inode);
 }   /*  End Function update_atime  */
 
+/**
+ *	update_mctime	-	update the mtime and ctime
+ *	@inode: inode accessed
+ *
+ *	Update the modified and changed times on an inode for writes to special
+ *	files such as fifos.  No change is forced if the timestamps are already
+ *	up-to-date or if the filesystem is readonly.
+ */
+ 
+void update_mctime (struct inode *inode)
+{
+	if (inode->i_mtime == CURRENT_TIME && inode->i_ctime == CURRENT_TIME)
+		return;
+	if ( IS_RDONLY (inode) ) return;
+	inode->i_ctime = inode->i_mtime = CURRENT_TIME;
+	mark_inode_dirty (inode);
+}   /*  End Function update_mctime  */
+
 
 /*
  *	Quota functions that want to walk the inode lists..
--- linux-2.4-odirect/fs/pipe.c.=K0004=.orig
+++ linux-2.4-odirect/fs/pipe.c
@@ -230,8 +230,7 @@ pipe_write(struct file *filp, const char
 	/* Signal readers asynchronously that there is more data.  */
 	wake_up_interruptible(PIPE_WAIT(*inode));
 
-	inode->i_ctime = inode->i_mtime = CURRENT_TIME;
-	mark_inode_dirty(inode);
+	update_mctime(inode);
 
 out:
 	up(PIPE_SEM(*inode));
--- linux-2.4-odirect/include/linux/fs.h.=K0004=.orig
+++ linux-2.4-odirect/include/linux/fs.h
@@ -201,6 +201,7 @@ extern int leases_enable, dir_notify_ena
 #include <asm/byteorder.h>
 
 extern void update_atime (struct inode *);
+extern void update_mctime (struct inode *);
 #define UPDATE_ATIME(inode) update_atime (inode)
 
 extern void buffer_init(unsigned long);