lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Thu, 04 Aug 2011 09:10:12 -0700
From:	Allison Henderson <>
To:	"Ted Ts'o" <>
CC:	Ext4 Developers List <>
Subject: Re: [PATCH 1/1 v3] ext4: fix xfstests 75, 112, 127 punch hole failure

On 08/04/2011 08:25 AM, Ted Ts'o wrote:
> On Thu, Aug 04, 2011 at 12:22:58AM -0700, Allison Henderson wrote:
>> Oh, I think we do avoid calling the unmap for this last condition
>> though.  The first and last page offsets are calculated earlier for
>> calling truncate_inode_pages_range to release all the pages in the
>> hole. The idea is that everything from first_page_offset to
>> last_page_offset covers all the page aligned pages in the hole.  So
>> then if offset and length are aligned, we basically end up with
>> first_page_offset = offset and last_page_offset = offset + length,
>> and the page_len will turn out to be zero.  Right math?  Maybe we
>> can add some comments or something to help clarify.
> Yeah, sorry, I wasn't clear enough about the condition.  Consider the
> situation where we punch the region:
>     4092 -- 8197
> In the previous section of code, we would zero out the byte ranges
> 4092--4095 and 8192--8197.  What's left is a completely page-aligned
> range, which would have already been taken care of already.  But since
> we're calculating based on offsets, I believe there will be an
> unnecessary call to ext4_unmap_page_range().

Oh I see, that makes sense now :)  I will add in something to check for 
that condition.

> BTW, the name ext4_unmap_page_range() is a bit confusing; maybe we
> should rename it to ext4_unmap_partial_page_buffers()?
> I know you were copying from the ext4_block_zero_page_range() function
> and its calling sequence (but in my opinion that function wasn't named
> well and the comments in that code aren't good either).
> I also wonder why we can't fold the functionality found in
> ext4_unmap_page_range() into ext4_block_zero_page_range().  Did you
> look into that option?

Yes, an earlier version of this patch looked a lot like that. (It was 
reviewed on an internal list before it came to the ext4 list, but I keep 
the version numbers so that people on both lists dont get confused).  I 
guess it's just a question of whether people would prefer one complex 
function or two simple functions. I will send v2 to the ext4 list so 
that people can get an idea of what the complex version looks like.

I do think ext4_unmap_partial_page_buffers is probably a more 
descriptive name though. If we choose to keep it as a separate function, 
I will add that in.

Allison Henderson

> Regards,
> 						- Ted

To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to
More majordomo info at

Powered by blists - more mailing lists