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

Stephen C. Tweedie (sct@redhat.com)
Fri, 30 May 2003 14:21:12 +0100


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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

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--- 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);

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