From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 086F147F786; Wed, 2 Sep 2026 16:35:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788366955; cv=none; b=hZFloCcg25Q+zuL3eM9YombtDHG9fJjmfV6EhTkWON2BQBaNPmrvKBr9fAvz7wHfi12STFr4TsXlsug+xz3kvEvMZ0qiLlA5Rr+PfO6hUYGMe620cEsI6uHIoO7eMu8PDohcpVF5dZ9KwAh8FbDUylozO52k7GdBRjos940gVxU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788366955; c=relaxed/simple; bh=sqNtSfdNCaTQb/2mf73osRumdi1Z06osl4U/LVAk7AU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=nPNuX8KDK84j0nXja06PXtPaVcFYaMlOnypygLB/igp7ivqT945A1LD90EXVYTFFkGP4WgsmnwoIs+yPpT4Cq77OEPLPeegFMOnSYsFB4t4GVkt3naMBp/j/LaQ/lExm00yD7PMZHOOy8+zWqaGoNYwg5MqvzaaAh2tRo7+ONZ4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=RUx12r4I; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="RUx12r4I" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8512B1F000E9; Wed, 2 Sep 2026 16:35:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788366953; bh=ac8jsX+DMtEi6vVSz6czKKoo3d1DKY5/tg/cm1MFQFw=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=RUx12r4IWkNLDsowdrG0tIOgZVYvTtRlYFpwS7Ps2MMhUDo8igPTsx5tqCIx+dq7Z P45rLsyOHNZ648U94ptQfeZK2A6TIPNQ1jReHuNNaBFn1FpxVy8yWXLcWIeku6ogf3 phduk3qLzEe+N5cPT55mwg37gegxI/Km0KI7fLBcmLItsmKIyiPbKfe055cCnOgsmT Hj6e5Xzpy/SOMfU4n1Jfo/4KJG55kbI+nqf+WVv1ur153KlNEiDkd3z+uNSX3O5xxx wK869ki2JRA8vPt7m9JGtU8shMYnwNuJVRQ2YKntYe6yvK8KFGuG1wfJG6pEikmfAv 4BdET61TLKMcQ== Message-ID: <86fc18f6-8c21-4738-9a10-64a2fa48cc1f@kernel.org> Date: Wed, 2 Sep 2026 18:35:48 +0200 Precedence: bulk X-Mailing-List: linux-xfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 3/4] mm: replace PF_KSWAPD flag with kthread_func() check To: Kefeng Wang , brauner@kernel.org, djwong@kernel.org, cem@kernel.org, akpm@linux-foundation.org, surenb@google.com, mhocko@suse.com, brendan.jackman@linux.dev, hannes@cmpxchg.org, ziy@nvidia.com, david@kernel.org, qi.zheng@linux.dev, shakeel.butt@linux.dev, ljs@kernel.org Cc: linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org References: <20260902131653.1338227-1-wangkefeng.wang@huawei.com> <20260902131653.1338227-4-wangkefeng.wang@huawei.com> From: "Vlastimil Babka (SUSE)" Content-Language: en-US Autocrypt: addr=vbabka@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 9/2/26 15:16, Kefeng Wang wrote: > The preceding commits removed the last consumer that propagated > PF_KSWAPD beyond kswapd itself (XFS btree split worker inheritance). > The only remaining setter of PF_KSWAPD is kswapd(), and every > current_is_kswapd() caller only needs to check whether the current > task *is* the kswapd thread, not whether it inherited the flag. > > Replace the flag-based test with kthread_func(current) == kswapd, > freeing the 0x00020000 PF flag bit. > > Signed-off-by: Kefeng Wang Acked-by: Vlastimil Babka (SUSE) > --- > include/linux/sched.h | 2 +- > include/linux/swap.h | 7 +------ > mm/vmscan.c | 10 ++++++++-- > tools/sched_ext/include/scx/common.bpf.h | 1 - > 4 files changed, 10 insertions(+), 10 deletions(-) > > diff --git a/include/linux/sched.h b/include/linux/sched.h > index 8b3d47a325cc..86394121b6c0 100644 > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -1809,7 +1809,7 @@ extern struct pid *cad_pid; > #define PF_USER_WORKER 0x00004000 /* Kernel thread cloned from userspace thread */ > #define PF_NOFREEZE 0x00008000 /* This thread should not be frozen */ > #define PF_KCOMPACTD 0x00010000 /* I am kcompactd */ > -#define PF_KSWAPD 0x00020000 /* I am kswapd */ > +#define PF__HOLE__00020000 0x00020000 > #define PF_MEMALLOC_NOFS 0x00040000 /* All allocations inherit GFP_NOFS. See memalloc_nfs_save() */ > #define PF_MEMALLOC_NOIO 0x00080000 /* All allocations inherit GFP_NOIO. See memalloc_noio_save() */ > #define PF_LOCAL_THROTTLE 0x00100000 /* Throttle writes only against the bdi I write to, > diff --git a/include/linux/swap.h b/include/linux/swap.h > index a72ecf12c00d..fc290e29e4a9 100644 > --- a/include/linux/swap.h > +++ b/include/linux/swap.h > @@ -25,12 +25,6 @@ > #define SWAP_FLAGS_VALID (SWAP_FLAG_PRIO_MASK | SWAP_FLAG_PREFER | \ > SWAP_FLAG_DISCARD | SWAP_FLAG_DISCARD_ONCE | \ > SWAP_FLAG_DISCARD_PAGES) > - > -static inline int current_is_kswapd(void) > -{ > - return current->flags & PF_KSWAPD; > -} > - > /* > * MAX_SWAPFILES defines the maximum number of swaptypes: things which can > * be swapped to. The swap type and the offset into that swap type are > @@ -339,6 +333,7 @@ void check_move_unevictable_folios(struct folio_batch *fbatch); > > extern void __meminit kswapd_run(int nid); > extern void __meminit kswapd_stop(int nid); > +bool current_is_kswapd(void); > > #ifdef CONFIG_SWAP > int add_swap_extent(struct swap_info_struct *sis, unsigned long start_page, > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 07ba86634b84..775d3f71a9de 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -7468,7 +7468,7 @@ static int kswapd(void *p) > * us from recursively trying to free more memory as we're > * trying to free the first piece of memory in the first place). > */ > - tsk->flags |= PF_MEMALLOC | PF_KSWAPD; > + tsk->flags |= PF_MEMALLOC; > set_freezable(); > > WRITE_ONCE(pgdat->kswapd_order, 0); > @@ -7518,11 +7518,17 @@ static int kswapd(void *p) > goto kswapd_try_sleep; > } > > - tsk->flags &= ~(PF_MEMALLOC | PF_KSWAPD); > + tsk->flags &= ~PF_MEMALLOC; > > return 0; > } > > +bool current_is_kswapd(void) > +{ > + return kthread_func(current) == kswapd; > +} > +EXPORT_SYMBOL_GPL(current_is_kswapd); > + > /* > * A zone is low on free memory or too fragmented for high-order memory. If > * kswapd should reclaim (direct reclaim is deferred), wake it up for the zone's > diff --git a/tools/sched_ext/include/scx/common.bpf.h b/tools/sched_ext/include/scx/common.bpf.h > index 76f5e025e107..3e095343ae84 100644 > --- a/tools/sched_ext/include/scx/common.bpf.h > +++ b/tools/sched_ext/include/scx/common.bpf.h > @@ -32,7 +32,6 @@ > #define PF_IO_WORKER 0x00000010 /* Task is an IO worker */ > #define PF_WQ_WORKER 0x00000020 /* I'm a workqueue worker */ > #define PF_KCOMPACTD 0x00010000 /* I am kcompactd */ > -#define PF_KSWAPD 0x00020000 /* I am kswapd */ > #define PF_KTHREAD 0x00200000 /* I am a kernel thread */ > #define PF_EXITING 0x00000004 > #define CLOCK_MONOTONIC 1