From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (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 BBFFB1552E8 for ; Thu, 22 Feb 2024 17:13:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708622030; cv=none; b=XHGOBmka0lxCbadOGSEytQ3CcdaoDzUjVRlFQ6hmfslB8PVDitX9jbFXvbMtFMDtV0IXv0p7YmuyU5NmWuswPyq4nJKw6ZSrCDdWQoz/6hEitfG35fKxLABIx0bmT/9Rw2t2oF5W5J3tEttpjRpQJgraTDYAmIviWfaLZh6TW8o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708622030; c=relaxed/simple; bh=j4iGKGJvrW6Ii4mYNEtnmzZcm5bFunGVCcPlyZKcVEM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=KmBy0z1xEtjyA02bGcrJOgYNEm9tsDKIyeJTCZatbAD7rxFv/mt+Bef9/xp0GDeZLvz0cdYRnFSt21Eu5I2apNU++Jc58uFwv0LwNVZUrIQTuhEg6SeavF2DHDadVGVhSShk+qxeBthaW7BX5jlYFhUqcOfWYu9EOCVsLpdXJyo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=cZQlKdRx; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="cZQlKdRx" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=1aaFYmWJOYjCrobR/mbIMeaCkuo57/YDbVrD4brlEWk=; b=cZQlKdRxi6wjlrIWrCdRrnIj3u 3CPSFPfq6MAzCgGH0WXKvG+eRNjvzVSuoPl6db3PSK8GnywBDDJ7AMyQdZWGs2ys+wJDXXOr8LPIy sq+WgpGSgv0TH0FaGbr2twnPwcVstav37EkmQ/2p8FCntUVUjYCnFCMimz0P+6odR8vqK480HM47J l6Qwiiba7nH8rvb4adRZRNXJRo4gtYrZo6UYVr/UeCs10c8MRPf9+JYYX8aaTQoCw+djkRmhF3364 tdyvPsLPu37VJYQ5MAiV9HGpUPn4lN2rrUwl48wEr7vvWLvPLqoo2HCheuUbOkOF8/XNEoGXNToHk q6CyZVsg==; Received: from willy by casper.infradead.org with local (Exim 4.97.1 #2 (Red Hat Linux)) id 1rdCdn-000000049c5-06P8; Thu, 22 Feb 2024 17:13:47 +0000 Date: Thu, 22 Feb 2024 17:13:46 +0000 From: Matthew Wilcox To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton Subject: Re: [PATCH v1] mm: remove total_mapcount() Message-ID: References: <20240222160943.622386-1-david@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240222160943.622386-1-david@redhat.com> On Thu, Feb 22, 2024 at 05:09:43PM +0100, David Hildenbrand wrote: > We always get a head page, so we can just naturally interpret is as a folio > (similar to other code). memfd seems rather confused about how to iterate over the page cache. Perhaps we could sort that out and then delete total_mapcount as a second patch? I haven't tested this at all, but ... Signed-off-by: Matthew Wilcox (Oracle) diff --git a/mm/memfd.c b/mm/memfd.c index d3a1ba4208c9..45e55b0e3cbe 100644 --- a/mm/memfd.c +++ b/mm/memfd.c @@ -29,28 +29,29 @@ #define MEMFD_TAG_PINNED PAGECACHE_TAG_TOWRITE #define LAST_SCAN 4 /* about 150ms max */ +static bool memfd_extra_refs(struct folio *folio) +{ + return folio_ref_count(folio) - folio_mapcount(folio) != + folio_nr_pages(folio); +} + static void memfd_tag_pins(struct xa_state *xas) { - struct page *page; + struct folio *folio; int latency = 0; - int cache_count; lru_add_drain(); xas_lock_irq(xas); - xas_for_each(xas, page, ULONG_MAX) { - cache_count = 1; - if (!xa_is_value(page) && - PageTransHuge(page) && !PageHuge(page)) - cache_count = HPAGE_PMD_NR; - - if (!xa_is_value(page) && - page_count(page) - total_mapcount(page) != cache_count) + xas_for_each(xas, folio, ULONG_MAX) { + /* Can we have shadow/swap entries in memfd? */ + if (xa_is_value(folio)) + continue; + + if (memfd_extra_refs(folio)) xas_set_mark(xas, MEMFD_TAG_PINNED); - if (cache_count != 1) - xas_set(xas, page->index + cache_count); - latency += cache_count; + latency++; if (latency < XA_CHECK_SCHED) continue; latency = 0; @@ -75,7 +76,6 @@ static void memfd_tag_pins(struct xa_state *xas) static int memfd_wait_for_pins(struct address_space *mapping) { XA_STATE(xas, &mapping->i_pages, 0); - struct page *page; int error, scan; memfd_tag_pins(&xas); @@ -83,7 +83,7 @@ static int memfd_wait_for_pins(struct address_space *mapping) error = 0; for (scan = 0; scan <= LAST_SCAN; scan++) { int latency = 0; - int cache_count; + struct folio *folio; if (!xas_marked(&xas, MEMFD_TAG_PINNED)) break; @@ -95,16 +95,10 @@ static int memfd_wait_for_pins(struct address_space *mapping) xas_set(&xas, 0); xas_lock_irq(&xas); - xas_for_each_marked(&xas, page, ULONG_MAX, MEMFD_TAG_PINNED) { + xas_for_each_marked(&xas, folio, ULONG_MAX, MEMFD_TAG_PINNED) { bool clear = true; - cache_count = 1; - if (!xa_is_value(page) && - PageTransHuge(page) && !PageHuge(page)) - cache_count = HPAGE_PMD_NR; - - if (!xa_is_value(page) && cache_count != - page_count(page) - total_mapcount(page)) { + if (memfd_extra_refs(folio)) { /* * On the last scan, we clean up all those tags * we inserted; but make a note that we still @@ -118,8 +112,7 @@ static int memfd_wait_for_pins(struct address_space *mapping) if (clear) xas_clear_mark(&xas, MEMFD_TAG_PINNED); - latency += cache_count; - if (latency < XA_CHECK_SCHED) + if (++latency < XA_CHECK_SCHED) continue; latency = 0;