Re: 2.6.19-rc2-mm1

Nick Piggin
2006-10-19T18:10:23Z

Carsten Otte wrote:
> Andrew Morton wrote:
>
>> The page we're writing into isn't locked, so there's no deadlock afaict.
>>
>> But then, I forget how xip works. Carsten, is it actually being used for
>> anything?
>>
>
> The comment may be superfluous. I did not quite understand the deadlock
> condition refered to by the comment in filemap, therefore I cut&pasted
> it over. I will send a patch that removes it.

Yes, it wasn't a good comment. Basically we can't hold the page lock and
then enter the page fault handler. mm-fix-pagecache-write-deadlocks.patch
has quite a lot of comments to explain it.

I don't believe filemap_xip holds the page lock, so you don't need to do
the atomic copy, and you don't need to do the fault_in_pages_readable.

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SUSE Labs, Novell Inc.
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