linux-kernel - Re: [patch|rfc] block: don't mark buffers beyond end of disk as mapped

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Date:	Tue, 01 May 2012 10:08:16 -0400
From:	Jeff Moyer <jmoyer@...hat.com>
To:	Nick Piggin <npiggin@...il.com>
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	jaxboe@...ionio.com, Kyle McMartin <kmcmarti@...hat.com>
Subject: Re: [patch|rfc] block: don't mark buffers beyond end of disk as mapped

Nick Piggin <npiggin@...il.com> writes:

> Not a bad fix. But it's kind of sad to have i_size checking logic also in
> block_read_full_page, that does not cope with this.
>
> I have found there are parts of the kernel (readahead) that try to read
> beyond EOF and seem to get angry if we return an error (by not
> marking uptodate in readpage) in that case though :(
>
> But, either way, I think it's very reasonable to not mark buffers beyond
> end of device as mapped. So I think your patch is fine.
>
> I guess for ext[234], it does not read metadata close to the end of the
> device or you were using 4K sized blocks?

Well, the test case just reads directly from the loop device, bypassing
the file system, and I did use 1KB blocks when making the file system, so
it is quite puzzling.

Thanks for taking a look, Nick.

Cheers,
Jeff
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