From: Dave Hansen <dave.hansen@intel.com>
To: "Kirill A. Shutemov" <kirill@shutemov.name>,
linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Hugh Dickins <hughd@google.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Vlastimil Babka <vbabka@suse.cz>,
Christoph Lameter <cl@gentwo.org>,
Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
Jerome Marchand <jmarchan@redhat.com>,
Yang Shi <yang.shi@linaro.org>,
Sasha Levin <sasha.levin@oracle.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: THP-enabled filesystem vs. FALLOC_FL_PUNCH_HOLE
Date: Fri, 4 Mar 2016 09:40:18 -0800 [thread overview]
Message-ID: <56D9C882.3040808@intel.com> (raw)
In-Reply-To: <20160304112603.GA9790@node.shutemov.name>
On 03/04/2016 03:26 AM, Kirill A. Shutemov wrote:
> On Thu, Mar 03, 2016 at 07:51:50PM +0300, Kirill A. Shutemov wrote:
>> Truncate and punch hole that only cover part of THP range is implemented
>> by zero out this part of THP.
>>
>> This have visible effect on fallocate(FALLOC_FL_PUNCH_HOLE) behaviour.
>> As we don't really create hole in this case, lseek(SEEK_HOLE) may have
>> inconsistent results depending what pages happened to be allocated.
>> Not sure if it should be considered ABI break or not.
>
> Looks like this shouldn't be a problem. man 2 fallocate:
>
> Within the specified range, partial filesystem blocks are zeroed,
> and whole filesystem blocks are removed from the file. After a
> successful call, subsequent reads from this range will return
> zeroes.
>
> It means we effectively have 2M filesystem block size.
The question is still whether this will case problems for apps.
Isn't 2MB a quote unusual block size? Wouldn't some files on a tmpfs
filesystem act like they have a 2M blocksize and others like they have
4k? Would that confuse apps?
--
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next prev parent reply other threads:[~2016-03-04 17:40 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1457023939-98083-1-git-send-email-kirill.shutemov@linux.intel.com>
2016-03-04 11:26 ` THP-enabled filesystem vs. FALLOC_FL_PUNCH_HOLE Kirill A. Shutemov
2016-03-04 17:40 ` Dave Hansen [this message]
2016-03-04 19:38 ` Hugh Dickins
2016-03-04 22:48 ` Kirill A. Shutemov
2016-03-04 23:05 ` Dave Chinner
2016-03-04 23:24 ` Kirill A. Shutemov
2016-03-05 22:38 ` Dave Chinner
2016-03-06 0:30 ` Kirill A. Shutemov
2016-03-06 23:03 ` Dave Chinner
2016-03-06 23:33 ` Kirill A. Shutemov
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