From: Dave Chinner <david@fromorbit.com>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Hugh Dickins <hughd@google.com>,
Dave Hansen <dave.hansen@intel.com>,
linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.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: Mon, 7 Mar 2016 10:03:36 +1100 [thread overview]
Message-ID: <20160306230336.GE11282@dastard> (raw)
In-Reply-To: <20160306003034.GA13704@node.shutemov.name>
On Sun, Mar 06, 2016 at 03:30:34AM +0300, Kirill A. Shutemov wrote:
> On Sun, Mar 06, 2016 at 09:38:11AM +1100, Dave Chinner wrote:
> > On Sat, Mar 05, 2016 at 02:24:12AM +0300, Kirill A. Shutemov wrote:
> > > Would it be acceptable for fallocate(FALLOC_FL_PUNCH_HOLE) to return
> > > -EBUSY (or other errno on your choice), if we cannot split the page
> > > right away?
> >
> > Which means THP are not transparent any more. What does an
> > application do when it gets an EBUSY, anyway?
>
> I guess it's reasonable to expect from an application to handle EOPNOTSUPP
> as FALLOC_FL_PUNCH_HOLE is not supported by some filesystems.
Yes, but this is usually done as a check at the program
initialisation to determine whether to issue hole punches at all.
It's not suppose to be a dynamic error.
> Although, non-consistent result from the same fd can be confusing.
Exactly.
> > And it's not just hole punching that has this problem. Direct IO is
> > going to have the same issue with invalidation of the mapped ranges
> > over the IO being done. XFS already WARNs when page cache
> > invalidation fails with EBUSY in direct IO, because that is
> > indicative of an application with a potential data corruption vector
> > and there's nothing we can do in the kernel code to prevent it.
>
> My current understanding is that for filesystems with persistent storage,
> in order to make THP any useful, we would need to implement writeback
> without splitting the huge page.
Algorithmically it is no different to filesytem block size < page
size writeback.
> At the moment, I have no idea how hard it would be..
THP support would effectively require us to remove PAGE_CACHE_SIZE
assumptions from all of the filesystem and buffer code. That's a
large chunk of work e.g. fs/buffer.c and any filesystem that uses
bufferheads for tracking filesystem block state through the page
cache.
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2016-03-06 23:03 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
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 [this message]
2016-03-06 23:33 ` Kirill A. Shutemov
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20160306230336.GE11282@dastard \
--to=david@fromorbit.com \
--cc=aarcange@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=cl@gentwo.org \
--cc=dave.hansen@intel.com \
--cc=hughd@google.com \
--cc=jmarchan@redhat.com \
--cc=kirill.shutemov@linux.intel.com \
--cc=kirill@shutemov.name \
--cc=linux-api@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=n-horiguchi@ah.jp.nec.com \
--cc=sasha.levin@oracle.com \
--cc=vbabka@suse.cz \
--cc=yang.shi@linaro.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).