linux-kernel - Re: [PATCH v2 (RESEND)] lockdep: Fix fs

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Message-Id: <20180307153305.16e5225d8a14d96436235eb1@linux-foundation.org>
Date:   Wed, 7 Mar 2018 15:33:05 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc:     peterz@...radead.org, mingo@...hat.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 (RESEND)] lockdep: Fix fs_reclaim warning.

On Wed, 28 Feb 2018 06:50:02 +0900 Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp> wrote:

> 
> This warning is caused by commit d92a8cfcb37ecd13 ("locking/lockdep: Rework
> FS_RECLAIM annotation") which replaced lockdep_set_current_reclaim_state()/
> lockdep_clear_current_reclaim_state() in __perform_reclaim() and
> lockdep_trace_alloc() in slab_pre_alloc_hook() with fs_reclaim_acquire()/
> fs_reclaim_release(). Since __kmalloc_reserve() from __alloc_skb() adds
> __GFP_NOMEMALLOC | __GFP_NOWARN to gfp_mask, and all reclaim path simply
> propagates __GFP_NOMEMALLOC, fs_reclaim_acquire() in slab_pre_alloc_hook()
> is trying to grab the 'fake' lock again when __perform_reclaim() already
> grabbed the 'fake' lock.

That's quite an audit trail.

Shouldn't we be doing a cc:stable here?  If so, which patch do we
identify as being fixed, with "Fixes:"?  d92a8cfcb37ecd13, I assume?

I'd never even noticed fs_reclaim_acquire() and friends before.  I do
wish they had "lockdep" in their names, and a comment to explain what
they do and why they exist.