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RE: [PATCH] incorrect error handling inside generic_file_direct_write

To: "'Christoph Hellwig'" <hch@xxxxxxxxxxxxx>
Subject: RE: [PATCH] incorrect error handling inside generic_file_direct_write
From: "Chen, Kenneth W" <kenneth.w.chen@xxxxxxxxx>
Date: Fri, 15 Dec 2006 10:53:18 -0800
Cc: "'Andrew Morton'" <akpm@xxxxxxxx>, "Dmitriy Monakhov" <dmonakhov@xxxxx>, "Dmitriy Monakhov" <dmonakhov@xxxxxxxxxx>, <linux-kernel@xxxxxxxxxxxxxxx>, "Linux Memory Management" <linux-mm@xxxxxxxxx>, <devel@xxxxxxxxxx>, <xfs@xxxxxxxxxxx>
In-reply-to: <20061215104341.GA20089@xxxxxxxxxxxxx>
Sender: xfs-bounce@xxxxxxxxxxx
Thread-index: AccgNeVMqKQOA+ZxSnqXd8lrl7/6aQAQ02YA
Christoph Hellwig wrote on Friday, December 15, 2006 2:44 AM
> So we're doing the sync_page_range once in __generic_file_aio_write
> with i_mutex held.
> 
> 
> >     mutex_lock(&inode->i_mutex);
> > -   ret = __generic_file_aio_write_nolock(iocb, iov, nr_segs,
> > -                   &iocb->ki_pos);
> > +   ret = __generic_file_aio_write(iocb, iov, nr_segs, pos);
> >     mutex_unlock(&inode->i_mutex);
> >  
> >     if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
> 
> And then another time after it's unlocked, this seems wrong.


I didn't invent that mess though.

I should've ask the question first: in 2.6.20-rc1, generic_file_aio_write
will call sync_page_range twice, once from __generic_file_aio_write_nolock
and once within the function itself.  Is it redundant?  Can we delete the
one in the top level function?  Like the following?


--- ./mm/filemap.c.orig 2006-12-15 09:02:58.000000000 -0800
+++ ./mm/filemap.c      2006-12-15 09:03:19.000000000 -0800
@@ -2370,14 +2370,6 @@ ssize_t generic_file_aio_write(struct ki
        ret = __generic_file_aio_write_nolock(iocb, iov, nr_segs,
                        &iocb->ki_pos);
        mutex_unlock(&inode->i_mutex);
-
-       if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
-               ssize_t err;
-
-               err = sync_page_range(inode, mapping, pos, ret);
-               if (err < 0)
-                       ret = err;
-       }
        return ret;
 }
 EXPORT_SYMBOL(generic_file_aio_write);


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