Linux-mm Archive on lore.kernel.org
 help / color / Atom feed
From: Michal Hocko <mhocko@kernel.org>
To: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: Vlastimil Babka <vbabka@suse.cz>,
	linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2] mm/kvmalloc: do not call kmalloc for size > KMALLOC_MAX_SIZE
Date: Mon, 5 Nov 2018 17:57:30 +0100
Message-ID: <20181105165730.GN4361@dhcp22.suse.cz> (raw)
In-Reply-To: <d033db53-129d-c031-db78-ba7f9fed5bf4@yandex-team.ru>

On Mon 05-11-18 19:19:28, Konstantin Khlebnikov wrote:
> 
> 
> On 05.11.2018 16:03, Vlastimil Babka wrote:
> > On 11/1/18 11:09 AM, Konstantin Khlebnikov wrote:
> > > Allocations over KMALLOC_MAX_SIZE could be served only by vmalloc.
> > > 
> > > Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
> > 
> > Makes sense regardless of warnings stuff.
> > 
> > Acked-by: Vlastimil Babka <vbabka@suse.cz>
> > 
> > But it must be moved below the GFP_KERNEL check!
> 
> But kmalloc cannot handle it regardless of GFP.
> 
> Ok maybe write something like this
> 
> if (size > KMALLOC_MAX_SIZE) {
> 	if (WARN_ON_ONCE((flags & GFP_KERNEL) != GFP_KERNEL)
> 		return NULL;
> 	goto do_vmalloc;
> }

Do we really have to be so defensive? I agree with Vlastimil that the
check should be done after GFP_KERNEL check (I should have noticed that).
kmalloc should already complain on the allocation size request.

> or fix that uncertainty right in vmalloc
> 
> For now comment in vmalloc declares
> 
>  *	Any use of gfp flags outside of GFP_KERNEL should be consulted
>  *	with mm people.

Which is what we want. There are some exceptional cases where using a
subset of GFP_KERNEL works fine (e.g. scope nofs/noio context).

-- 
Michal Hocko
SUSE Labs

      parent reply index

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-01  9:12 [PATCH] mm/kvmalloc: do not confuse kmalloc with page order over MAX_ORDER Konstantin Khlebnikov
2018-11-01  9:33 ` Michal Hocko
2018-11-01 10:09 ` [PATCH 2] mm/kvmalloc: do not call kmalloc for size > KMALLOC_MAX_SIZE Konstantin Khlebnikov
2018-11-01 10:24   ` Michal Hocko
2018-11-01 10:48     ` Konstantin Khlebnikov
2018-11-01 12:55       ` Michal Hocko
2018-11-01 16:42         ` Konstantin Khlebnikov
2018-11-01 16:55           ` Michal Hocko
2018-11-05 13:03   ` Vlastimil Babka
2018-11-05 16:19     ` Konstantin Khlebnikov
2018-11-05 16:52       ` Vlastimil Babka
2018-11-05 16:57       ` Michal Hocko [this message]

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=20181105165730.GN4361@dhcp22.suse.cz \
    --to=mhocko@kernel.org \
    --cc=akpm@linux-foundation.org \
    --cc=khlebnikov@yandex-team.ru \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=vbabka@suse.cz \
    /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
	public-inbox-index linux-mm

Example config snippet for mirrors

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.git