From: Jan Kara <jack@suse.cz>
To: Michal Hocko <mhocko@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>,
Michal Hocko <mhocko@suse.com>, Theodore Ts'o <tytso@mit.edu>,
Jan Kara <jack@suse.cz>
Subject: Re: [PATCH 17/17] jbd2: get rid of superfluous __GFP_REPEAT
Date: Mon, 30 May 2016 15:09:01 +0200 [thread overview]
Message-ID: <20160530130901.GE3690@quack2.suse.cz> (raw)
In-Reply-To: <1464599699-30131-18-git-send-email-mhocko@kernel.org>
On Mon 30-05-16 11:14:59, Michal Hocko wrote:
> From: Michal Hocko <mhocko@suse.com>
>
> jbd2_alloc is explicit about its allocation preferences wrt. the
> allocation size. Sub page allocations go to the slab allocator
> and larger are using either the page allocator or vmalloc. This
> is all good but the logic is unnecessarily complex.
> 1) as per Ted, the vmalloc fallback is a left-over:
> : jbd2_alloc is only passed in the bh->b_size, which can't be >
> : PAGE_SIZE, so the code path that calls vmalloc() should never get
> : called. When we conveted jbd2_alloc() to suppor sub-page size
> : allocations in commit d2eecb039368, there was an assumption that it
> : could be called with a size greater than PAGE_SIZE, but that's
> : certaily not true today.
> Moreover vmalloc allocation might even lead to a deadlock because
> the callers expect GFP_NOFS context while vmalloc is GFP_KERNEL.
>
> 2) __GFP_REPEAT for requests <= PAGE_ALLOC_COSTLY_ORDER is ignored
> since the flag was introduced.
>
> Let's simplify the code flow and use the slab allocator for sub-page
> requests and the page allocator for others. Even though order > 0 is
> not currently used as per above leave that option open.
>
> Cc: "Theodore Ts'o" <tytso@mit.edu>
> Cc: Jan Kara <jack@suse.cz>
> Signed-off-by: Michal Hocko <mhocko@suse.com>
The patch looks good. You can add:
Reviewed-by: Jan Kara <jack@suse.cz>
Since the patch is in pretty stable parts of JBD2 I think it is fine to
merge it through Andrew's tree with the rest of the series.
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
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prev parent reply other threads:[~2016-05-30 13:09 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-30 9:14 [PATCH 0/19] get rid of superfluous __GFP_REPEAT Michal Hocko
2016-05-30 9:14 ` [PATCH 01/17] tree wide: get rid of __GFP_REPEAT for order-0 allocations part I Michal Hocko
2016-05-30 9:14 ` [PATCH 02/17] x86: get rid of superfluous __GFP_REPEAT Michal Hocko
2016-05-30 9:14 ` [PATCH 03/17] x86/efi: " Michal Hocko
2016-05-30 9:14 ` [PATCH 04/17] arm: " Michal Hocko
2016-06-01 16:24 ` Russell King - ARM Linux
2016-06-02 6:32 ` Michal Hocko
2016-07-20 20:59 ` Andrew Morton
2016-05-30 9:14 ` [PATCH 05/17] arm64: " Michal Hocko
2016-05-30 9:14 ` [PATCH 06/17] arc: " Michal Hocko
2016-05-30 9:14 ` [PATCH 07/17] mips: " Michal Hocko
2016-05-30 9:14 ` [PATCH 08/17] nios2: " Michal Hocko
2016-05-30 9:14 ` [PATCH 09/17] parisc: " Michal Hocko
2016-05-30 9:14 ` [PATCH 10/17] score: " Michal Hocko
2016-05-30 9:14 ` [PATCH 11/17] powerpc: " Michal Hocko
2016-05-30 9:14 ` [PATCH 12/17] sparc: " Michal Hocko
2016-05-30 18:23 ` David Miller
2016-05-30 9:14 ` [PATCH 13/17] s390: " Michal Hocko
2016-05-30 9:14 ` [PATCH 14/17] sh: " Michal Hocko
2016-05-30 9:14 ` [PATCH 15/17] tile: " Michal Hocko
2016-05-30 9:14 ` [PATCH 16/17] unicore32: " Michal Hocko
2016-05-30 9:14 ` [PATCH 17/17] jbd2: " Michal Hocko
2016-05-30 13:09 ` Jan Kara [this message]
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