linux-ext4 - Re: [PATCH v4 21/22] Add support for pmd

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Message-ID: <20131223185433.GA18067@node.dhcp.inet.fi>
Date:	Mon, 23 Dec 2013 20:54:33 +0200
From:	"Kirill A. Shutemov" <kirill@...temov.name>
To:	Matthew Wilcox <matthew@....cx>
Cc:	Matthew Wilcox <matthew.r.wilcox@...el.com>,
	linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
	linux-mm@...ck.org, Andrea Arcangeli <aarcange@...hat.com>
Subject: Re: [PATCH v4 21/22] Add support for pmd_faults

On Mon, Dec 23, 2013 at 11:42:22AM -0700, Matthew Wilcox wrote:
> > Do you know anyone who relay on SIGBUS for correctness?
> 
> Oh, I remember the real reason now.  If we install a PMD that hangs off
> the end of the file then by reading past i_size, we can read the blocks of
> whatever happens to be in storage after the end of the file, which could
> be another file's data.  This doesn't happen for the PTE case because the
> existing code only works for filesystems with a block size == PAGE_SIZE.

I see. It's valid reason. Probably, it's better to add comment there.

-- 
 Kirill A. Shutemov
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