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Re: WARNING in xfs_lwr.c, xfs_write()

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: WARNING in xfs_lwr.c, xfs_write()
From: Roman Kononov <roman@xxxxxxxxxxxxxx>
Date: Sun, 23 May 2010 09:23:44 -0500
Cc: xfs@xxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx
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In-reply-to: <20100523101856.GL2150@dastard>
References: <20100523002023.41f5a5c8@xxxxxxxxxxxxxxxxxxxxxxx> <20100523101856.GL2150@dastard>
On 2010-05-23, 20:18:56 +1000, Dave Chinner <david@xxxxxxxxxxxxx> wrote:
> You've got some workload that is mixing direct IO writes with some
> form of buffered or mmap IO on the same file and they are racing.
> Mixing different types of IO on the one inode is also known as A
> Really Bad Idea because there is no guarantee of coherency between
> them....
> 
> Can you find out what the application is triggering this?

This is severely modified Postgresql, which does mix direct IO with
buffered one.

You say "they are racing". Do you mean that this can cause file system
corruption? Doest it simply warn that direct user data races with
buffered user data and one of them wins? This warning "taints" the
kernel. Should it be safe to do different types of IOs on different
non-overlapping 4-KiB-aligned regions of the same file (I am unsure
if this is what the application really does)?

Thanks,

Roman

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