linux-kernel - Re: [PATCH next] sysfs: fix some bin_vm

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Date:	Mon, 23 Mar 2009 01:44:56 +0000 (GMT)
From:	Hugh Dickins <hugh@...itas.com>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
cc:	"Eric W. Biederman" <ebiederm@...stanetworks.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Tejun Heo <tj@...nel.org>, Kay Sievers <kay.sievers@...y.org>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Nick Piggin <npiggin@...e.de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH next] sysfs: fix some bin_vm_ops errors

On Mon, 23 Mar 2009, Benjamin Herrenschmidt wrote:
> On Sun, 2009-03-22 at 18:33 +0000, Hugh Dickins wrote:
> > Commit 86c9508eb1c0ce5aa07b5cf1d36b60c54efc3d7a
> > "sysfs: don't block indefinitely for unmapped files" in linux-next
> > crashes the PowerMac G5 when X starts up.  It's caught out by the way
> > powerpc's pci_mmap of legacy_mem uses shmem_zero_setup(), substituting
> > a new vma->vm_file whose private_data no longer points to the bin_buffer
> > (substitution done because some versions of X crash if that mmap fails).
> > 
> > The fix to this is straightforward: the original vm_file is fput() in
> > that case, so this mmap won't block sysfs at all, so just don't switch
> > over to bin_vm_ops if vm_file has changed.
> 
> Looks good, though we should probably also add a comment to your code
> to make it clear why the test is here.

Right, done.

> 
> The fix should probably go into .29...

No, this is just a linux-next or mmotm thing.  (I probably misled
you by quoting the commit id: though helpful, that is confusing.)

Hugh
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