linux-kernel - Re: [PATCH 0/5] Fix races & improve the radix tree iterator patterns

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Date:	Thu, 28 Jan 2016 10:17:41 +0300
From:	Konstantin Khlebnikov <koct9i@...il.com>
To:	Matthew Wilcox <matthew.r.wilcox@...el.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>,
	Ohad Ben-Cohen <ohad@...ery.com>,
	Matthew Wilcox <willy@...ux.intel.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [PATCH 0/5] Fix races & improve the radix tree iterator patterns

On Thu, Jan 28, 2016 at 12:17 AM, Matthew Wilcox
<matthew.r.wilcox@...el.com> wrote:
> From: Matthew Wilcox <willy@...ux.intel.com>
>
> The first two patches here are bugfixes, and I would like to see them
> make their way into stable ASAP since they can lead to data corruption
> (very low probabilty).
>
> The last three patches do not qualify as bugfixes.  They simply improve
> the standard pattern used to do radix tree iterations by removing the
> 'goto restart' part.  Partially this is because this is an ugly &
> confusing goto, and partially because with multi-order entries in the
> tree, it'll be more likely that we'll see an indirect_ptr bit, and
> it's more efficient to kep going from the point of the iteration we're
> currently in than restart from the beginning each time.

Ack  whole set.

I think we should go deeper in hide dereference/retry inside iterator.
Something like radix_tree_for_each_data(data, slot, root, iter, start).
I'll prepare patch for that.

>
> Matthew Wilcox (5):
>   radix-tree: Fix race in gang lookup
>   hwspinlock: Fix race between radix tree insertion and lookup
>   btrfs: Use radix_tree_iter_retry()
>   mm: Use radix_tree_iter_retry()
>   radix-tree,shmem: Introduce radix_tree_iter_next()
>
>  drivers/hwspinlock/hwspinlock_core.c |  4 +++
>  fs/btrfs/tests/btrfs-tests.c         |  3 +-
>  include/linux/radix-tree.h           | 31 +++++++++++++++++++++
>  lib/radix-tree.c                     | 12 ++++++--
>  mm/filemap.c                         | 53 ++++++++++++------------------------
>  mm/shmem.c                           | 30 ++++++++++----------
>  6 files changed, 78 insertions(+), 55 deletions(-)
>
> --
> 2.7.0.rc3
>
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