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Re: bogus b_data pointer?


On Apr 6, 2005, at 1:04 AM, Arjan van de Ven wrote:

On Tue, 2005-04-05 at 16:47 -0700, Can Sar wrote:
Hi,

I've instrumented the mark_buffer_dirty routine of the kernel to print
the address that b_data points to for a simple block device driver I
got from http://lwn.net/Articles/58720/. I get perfectly valid
addresses most of the time, except that sometimes the pointer has the
value of 0x400. I have been looking at this for a very long time and I
have no idea what could be causing this?
Does anyone have any ideas?


if the page is in highmem b_data doesn't mean what you think it means.
In fact I would argue that anyone using b_data is buggy....


That was my initial thought, but on the other hand, the machine in question only has 256 MB of RAM. IS that irrelevant? What would I have to do to fix this?

Thanks,
Can


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