Linux-mm Archive on lore.kernel.org
 help / color / Atom feed
From: Song Liu <songliubraving@fb.com>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Linux-MM <linux-mm@kvack.org>,
	Matthew Wilcox <matthew.wilcox@oracle.com>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Kernel Team <Kernel-team@fb.com>,
	William Kucharski <william.kucharski@oracle.com>,
	"Chad Mynhier" <chad.mynhier@oracle.com>,
	Mike Kravetz <mike.kravetz@oracle.com>
Subject: Re: [PATCH v2 3/3] mm,thp: add read-only THP support for (non-shmem) FS
Date: Fri, 21 Jun 2019 13:08:39 +0000
Message-ID: <B83B2259-7CF5-411E-BC4C-7112657FC48E@fb.com> (raw)
In-Reply-To: <20190621125810.llsqslfo52nfh5g7@box>


Hi Kirill,

> On Jun 21, 2019, at 5:58 AM, Kirill A. Shutemov <kirill@shutemov.name> wrote:
> 
> On Fri, Jun 14, 2019 at 11:22:04AM -0700, Song Liu wrote:
>> This patch is (hopefully) the first step to enable THP for non-shmem
>> filesystems.
>> 
>> This patch enables an application to put part of its text sections to THP
>> via madvise, for example:
>> 
>>    madvise((void *)0x600000, 0x200000, MADV_HUGEPAGE);
>> 
>> We tried to reuse the logic for THP on tmpfs. The following functions are
>> renamed to reflect the new functionality:
>> 
>> 	collapse_shmem()	=>  collapse_file()
>> 	khugepaged_scan_shmem()	=>  khugepaged_scan_file()
>> 
>> Currently, write is not supported for non-shmem THP. This is enforced by
>> taking negative i_writecount. Therefore, if file has THP pages in the
>> page cache, open() to write will fail. To update/modify the file, the
>> user need to remove it first.
>> 
>> An EXPERIMENTAL config, READ_ONLY_THP_FOR_FS, is added to gate this
>> feature.
> 
> Please document explicitly that the feature opens local DoS attack: any
> user with read access to file can block write to the file by using
> MADV_HUGEPAGE for a range of the file.
> 
> As is it only has to be used with trusted userspace.
> 
> We also might want to have mount option in addition to Kconfig option to
> enable the feature on per-mount basis.

This behavior has been removed from v3 to v5. 

Thanks,
Song

  reply index

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-14 18:22 [PATCH v2 0/3] Enable THP for text section of non-shmem files Song Liu
2019-06-14 18:22 ` [PATCH v2 1/3] mm: check compound_head(page)->mapping in filemap_fault() Song Liu
2019-06-17 14:59   ` Rik van Riel
2019-06-14 18:22 ` [PATCH v2 2/3] mm,thp: stats for file backed THP Song Liu
2019-06-17 15:00   ` Rik van Riel
2019-06-21 12:50   ` Kirill A. Shutemov
2019-06-21 14:09     ` Song Liu
2019-06-14 18:22 ` [PATCH v2 3/3] mm,thp: add read-only THP support for (non-shmem) FS Song Liu
2019-06-17 15:42   ` Rik van Riel
2019-06-21 12:58   ` Kirill A. Shutemov
2019-06-21 13:08     ` Song Liu [this message]
2019-06-21 13:11       ` Kirill A. Shutemov
2019-06-18 21:12 ` [PATCH v2 0/3] Enable THP for text section of non-shmem files Andrew Morton
2019-06-18 21:48   ` Song Liu
2019-06-20  1:13     ` Andrew Morton
2019-06-20  2:04       ` Song Liu
2019-06-19  6:26   ` Song Liu

Reply instructions:

You may reply publically 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=B83B2259-7CF5-411E-BC4C-7112657FC48E@fb.com \
    --to=songliubraving@fb.com \
    --cc=Kernel-team@fb.com \
    --cc=chad.mynhier@oracle.com \
    --cc=kirill.shutemov@linux.intel.com \
    --cc=kirill@shutemov.name \
    --cc=linux-mm@kvack.org \
    --cc=matthew.wilcox@oracle.com \
    --cc=mike.kravetz@oracle.com \
    --cc=william.kucharski@oracle.com \
    /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

Linux-mm Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-mm/0 linux-mm/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-mm linux-mm/ https://lore.kernel.org/linux-mm \
		linux-mm@kvack.org linux-mm@archiver.kernel.org
	public-inbox-index linux-mm


Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kvack.linux-mm


AGPL code for this site: git clone https://public-inbox.org/ public-inbox