From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 272C0C07CB1 for ; Mon, 27 Nov 2023 15:51:17 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B7A116B02D5; Mon, 27 Nov 2023 10:51:16 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id B28916B02DB; Mon, 27 Nov 2023 10:51:16 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9F1286B02DF; Mon, 27 Nov 2023 10:51:16 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 8B7B06B02D5 for ; Mon, 27 Nov 2023 10:51:16 -0500 (EST) Received: from smtpin10.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 5D5851A02CD for ; Mon, 27 Nov 2023 15:51:16 +0000 (UTC) X-FDA: 81504173352.10.228C3E1 Received: from mgamail.intel.com (mgamail.intel.com [192.55.52.43]) by imf23.hostedemail.com (Postfix) with ESMTP id 0562914002A for ; Mon, 27 Nov 2023 15:51:13 +0000 (UTC) Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=XvSpIbgE; dmarc=pass (policy=none) header.from=intel.com; spf=none (imf23.hostedemail.com: domain of fabio.maria.de.francesco@linux.intel.com has no SPF policy when checking 192.55.52.43) smtp.mailfrom=fabio.maria.de.francesco@linux.intel.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1701100274; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=UQTyX8hpX459zOgjx/XEAUWeEFdy2g9idL6VCf804ck=; b=QVhmBNXv7A+WV5op8k7z63Ug45LIiGNKcpRybU7FzBJKmVvBjC/taNgcg/dzp5gEUhP+nb AP7CrnWWKu+nbUrUbLBXrmy9fPTx0gUKnEc5X74T6wL2ieyBJbvHEXJO0nnsiKODL5OR9R 40SqELPJvB+vmFekMDNliISWuEWVqE4= ARC-Authentication-Results: i=1; imf23.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=XvSpIbgE; dmarc=pass (policy=none) header.from=intel.com; spf=none (imf23.hostedemail.com: domain of fabio.maria.de.francesco@linux.intel.com has no SPF policy when checking 192.55.52.43) smtp.mailfrom=fabio.maria.de.francesco@linux.intel.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1701100274; a=rsa-sha256; cv=none; b=kdbD2CAyNI0bjvq1SpHLZ9s7G+KZFxhJu8mQ5j2YbRdCwwhgPLKv/xp8ZFin4EP4woFNjx lfpcgugvgR7pBwnQF6Om4eW66w6uk9n4CAu3kaZ8wRQeCT9YZ4y8sU+6JuxMXLCRSVeWCW 1TnWxuk/3RSn60MTmgV7ALjwOasAGFc= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1701100274; x=1732636274; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=877FtVHBgk7LHCmul90sfUJeTy1UTnHAb0oeqCMHxH8=; b=XvSpIbgEW1BTFvQDxar96Ey0DaGD3XMvoraFr0LBIuJbhPdQT8dgX4uU WERWl3pB5pAnLP4094sctBxFus1uFaEYSnePNm1EJfCSa6lrIeNh+LCQK B649zlGLARoBBBNagOll12nxCSa8GYD8KmRtzHHcFtk1gCR8h/PQk7VZx TE+SLK040wDbZ360ajwroUJ1vMlznUP+9bYqD0A9gzVMSaX2S9LHFdREk x44PT66QYc9hJm5b8K2RW4041bul3Vu7yNlDLY0IK+mkdPGc4D+7hzLl0 Gf5EtF0CwaVFYudKnP6X7muMfgdXMZb8e39f0LDrzl6cwnCbZFKg4WAzT A==; X-IronPort-AV: E=McAfee;i="6600,9927,10907"; a="478921467" X-IronPort-AV: E=Sophos;i="6.04,231,1695711600"; d="scan'208";a="478921467" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 Nov 2023 07:51:11 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10907"; a="834357802" X-IronPort-AV: E=Sophos;i="6.04,231,1695711600"; d="scan'208";a="834357802" Received: from fdefranc-mobl3.ger.corp.intel.com (HELO fdefranc-mobl3.localnet) ([10.213.15.40]) by fmsmga008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 Nov 2023 07:51:10 -0800 From: "Fabio M. De Francesco" To: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Ira Weiny Subject: Re: [PATCH 1006/1007] mm/swapfile: Replace kmap_atomic() with kmap_local_page() Date: Mon, 27 Nov 2023 16:51:07 +0100 Message-ID: <12332144.O9o76ZdvQC@fdefranc-mobl3> Organization: intel In-Reply-To: <20231127154601.585849-1-fabio.maria.de.francesco@linux.intel.com> References: <20231127154601.585849-1-fabio.maria.de.francesco@linux.intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 0562914002A X-Stat-Signature: 8hfxfkm99k1opmtirf6w6opbtibcrism X-HE-Tag: 1701100273-548150 X-HE-Meta: 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 7ETmWSK8 Y6Lqw/Fv9BFYLdhtTED4AJbTl302xKW4Sq1hvLQ7tnHMkmHI2pQpaMuEeE3RtvQKLpfjPrhSyKmvcfY8HXRtP8vUK/6IWy6bYX0HE/+mXpA9IjPCXFemrrVR+C2h/7tM0ge8i+mUsqqxwgpgtom7abS88Ag74h16VC+vdmqVyPQRv4TM62z940AbJQtbJRupzC6Xmliq1VXjwrpigfJ8HQvh5pW7f0U5g6HRF5bNUd/OESkXKRnBCqqoFQ6J2WRt2/gXi X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Please discard this patch for a mistake in the subject. Fabio On Monday, 27 November 2023 16:45:53 CET Fabio M. De Francesco wrote: > kmap_atomic() has been deprecated in favor of kmap_local_page(). > > Therefore, replace kmap_atomic() with kmap_local_page() in > swapfile.c. > > kmap_atomic() is implemented like a kmap_local_page() which also > disables page-faults and preemption (the latter only in !PREEMPT_RT > kernels). The kernel virtual addresses returned by these two API are > only valid in the context of the callers (i.e., they cannot be handed to > other threads). > > With kmap_local_page() the mappings are per thread and CPU local like > in kmap_atomic(); however, they can handle page-faults and can be called > from any context (including interrupts). The tasks that call > kmap_local_page() can be preempted and, when they are scheduled to run > again, the kernel virtual addresses are restored and are still valid. > > In mm/swapfile.c, the blocks of code between the mappings and un-mappings > do not depend on the above-mentioned side effects of kmap_aatomic(), so > that the mere replacements of the old API with the new one is all that is > required (i.e., there is no need to explicitly call pagefault_disable() > and/or preempt_disable()). > > Cc: Ira Weiny > Signed-off-by: Fabio M. De Francesco > --- > mm/swapfile.c | 34 +++++++++++++++++----------------- > 1 file changed, 17 insertions(+), 17 deletions(-) > > diff --git a/mm/swapfile.c b/mm/swapfile.c > index 4bc70f459164..8be70912e298 100644 > --- a/mm/swapfile.c > +++ b/mm/swapfile.c > @@ -1495,9 +1495,9 @@ int swp_swapcount(swp_entry_t entry) > > do { > page = list_next_entry(page, lru); > - map = kmap_atomic(page); > + map = kmap_local_page(page); > tmp_count = map[offset]; > - kunmap_atomic(map); > + kunmap_local(map); > > count += (tmp_count & ~COUNT_CONTINUED) * n; > n *= (SWAP_CONT_MAX + 1); > @@ -3477,9 +3477,9 @@ int add_swap_count_continuation(swp_entry_t entry, > gfp_t gfp_mask) if (!(count & COUNT_CONTINUED)) > goto out_unlock_cont; > > - map = kmap_atomic(list_page) + offset; > + map = kmap_local_page(list_page) + offset; > count = *map; > - kunmap_atomic(map); > + kunmap_local(map); > > /* > * If this continuation count now has some space in it, > @@ -3529,7 +3529,7 @@ static bool swap_count_continued(struct > swap_info_struct *si, spin_lock(&si->cont_lock); > offset &= ~PAGE_MASK; > page = list_next_entry(head, lru); > - map = kmap_atomic(page) + offset; > + map = kmap_local_page(page) + offset; > > if (count == SWAP_MAP_MAX) /* initial increment from swap_map */ > goto init_map; /* jump over SWAP_CONT_MAX checks */ > @@ -3539,27 +3539,27 @@ static bool swap_count_continued(struct > swap_info_struct *si, * Think of how you add 1 to 999 > */ > while (*map == (SWAP_CONT_MAX | COUNT_CONTINUED)) { > - kunmap_atomic(map); > + kunmap_local(map); > page = list_next_entry(page, lru); > BUG_ON(page == head); > - map = kmap_atomic(page) + offset; > + map = kmap_local_page(page) + offset; > } > if (*map == SWAP_CONT_MAX) { > - kunmap_atomic(map); > + kunmap_local(map); > page = list_next_entry(page, lru); > if (page == head) { > ret = false; /* add count continuation */ > goto out; > } > - map = kmap_atomic(page) + offset; > + map = kmap_local_page(page) + offset; > init_map: *map = 0; /* we didn't zero the page */ > } > *map += 1; > - kunmap_atomic(map); > + kunmap_local(map); > while ((page = list_prev_entry(page, lru)) != head) { > - map = kmap_atomic(page) + offset; > + map = kmap_local_page(page) + offset; > *map = COUNT_CONTINUED; > - kunmap_atomic(map); > + kunmap_local(map); > } > ret = true; /* incremented */ > > @@ -3569,21 +3569,21 @@ init_map: *map = 0; /* we didn't zero the page */ > */ > BUG_ON(count != COUNT_CONTINUED); > while (*map == COUNT_CONTINUED) { > - kunmap_atomic(map); > + kunmap_local(map); > page = list_next_entry(page, lru); > BUG_ON(page == head); > - map = kmap_atomic(page) + offset; > + map = kmap_local_page(page) + offset; > } > BUG_ON(*map == 0); > *map -= 1; > if (*map == 0) > count = 0; > - kunmap_atomic(map); > + kunmap_local(map); > while ((page = list_prev_entry(page, lru)) != head) { > - map = kmap_atomic(page) + offset; > + map = kmap_local_page(page) + offset; > *map = SWAP_CONT_MAX | count; > count = COUNT_CONTINUED; > - kunmap_atomic(map); > + kunmap_local(map); > } > ret = count == COUNT_CONTINUED; > }