From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta1.migadu.com (out-192.mta1.migadu.com [95.215.58.192]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6DA3F489FC2 for ; Fri, 2 Oct 2026 09:57:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.192 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790935044; cv=none; b=d4Yg8MI3xtcHyA91A1eBcciSfYR5h77tbyzwgGNPfBvFTtCAs49Ov0GrdzFtD38yzDJx4aeT6pwyLTSrKVYxL/VXeF4ZxGIpxsW6heyLdU3GgyYkSoFmxU8yQDqtQQiffHrCrIZaoaxBwZnBf/fXRRdZjCbjZr342S13LJUDXsk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790935044; c=relaxed/simple; bh=w0gztRkUfUOE/+G3kO+FMjzHwEfBAB20UzLM0QrOt9Y=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Ta2d79JNU/vUxC/PjJXFWczPC7T0alp8JoiUTu0A3VGYdVTvvHLhgZoHXTFVM5t4nUocFr+iJGkaB0xgxUHj86mihyq/5qkRGlkOfewRfiS7r1ew1+vzfBfZKKCT7lW2xs2WSVWTE7Vb3dVAnx0C5SLXgL2pBKp8oaIxLCrXMmk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=GaD7IpxX; arc=none smtp.client-ip=95.215.58.192 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="GaD7IpxX" X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=w0gztRkUfUOE/+G3kO+FMjzHwEfBAB20UzLM0QrOt9Y=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1790935040; v=1; x=1791539840; b=GaD7IpxXO6CM35PABCzhX2+LSFy/bQkY5xuuSW+0iIu3e9aJ4Tqz3X2BQde/PIJ+VaLyMmCn wgjwLykiwW7VFqjP1QSQ5r2uD2eKbYTEda3u3qBq3/djH5KE5ew9X1zhTMF6ghjbRstLUVDR75D beWR0HeEkh3ZVicmQmNo//4g= X-Envelope-To: linux-kernel@vger.kernel.org Received: by mta12.migadu.com with ESMTPS id 6a7be061ef33c288; Fri, 02 Oct 2026 09:57:19 +0000 X-Mizu-Trace-ID: 6a7be061ef33c288 X-Migadu-Flow: FLOW_OUT From: Usama Arif To: Andrew Morton , david@kernel.org, chrisl@kernel.org, kasong@tencent.com, ljs@kernel.org, ziy@nvidia.com, linux-mm@kvack.org Cc: ying.huang@linux.alibaba.com, Baoquan He , willy@infradead.org, youngjun.park@lge.com, hannes@cmpxchg.org, riel@surriel.com, shakeel.butt@linux.dev, alex@ghiti.fr, kas@kernel.org, baohua@kernel.org, dev.jain@arm.com, baolin.wang@linux.alibaba.com, Nico Pache , Liam R. Howlett , ryan.roberts@arm.com, Vlastimil Babka , lance.yang@linux.dev, linux-kernel@vger.kernel.org, nphamcs@gmail.com, shikemeng@huaweicloud.com, yosry@kernel.org, qi.zheng@linux.dev, luizcap@redhat.com, kernel-team@meta.com, Usama Arif Subject: [PATCH v8 23/30] mm/mincore: report PMD swap-cache residency Date: Fri, 2 Oct 2026 02:52:37 -0700 Message-ID: <20261002095503.3585565-24-usama.arif@linux.dev> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261002095503.3585565-1-usama.arif@linux.dev> References: <20261002095503.3585565-1-usama.arif@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit mincore_pte_range() reports every page under a huge PMD as resident. That is wrong for a swapped-out one: mincore() would tell userspace that memory it will have to fault in is already in core. A PMD swap entry is only a compact encoding for HPAGE_PMD_NR slots, so answer from the swap cache instead. One PMD-sized folio covering the range makes every page resident exactly when that folio is uptodate; an empty cache makes none of them; and if the folio was split while the entry stayed in place, fall back to looking up each covered slot as mincore_swap() does for a PTE swap entry. Signed-off-by: Usama Arif --- mm/mincore.c | 47 ++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 46 insertions(+), 1 deletion(-) diff --git a/mm/mincore.c b/mm/mincore.c index c086836bc4bcc..1846c6f68ae63 100644 --- a/mm/mincore.c +++ b/mm/mincore.c @@ -85,6 +85,48 @@ static unsigned char mincore_swap(swp_entry_t entry, bool shmem) return present; } +#ifdef CONFIG_THP_SWAP +static void mincore_pmd_swap(swp_entry_t entry, unsigned long addr, + unsigned long end, unsigned char *vec) +{ + unsigned long haddr = addr & HPAGE_PMD_MASK; + unsigned long start = (addr - haddr) >> PAGE_SHIFT; + unsigned long nr = (end - addr) >> PAGE_SHIFT; + struct folio *folio; + enum swap_pmd_cache state; + int i; + + state = swap_pmd_cache_lookup(entry, &folio); + if (state == SWAP_PMD_CACHE_HUGE) { + memset(vec, folio_test_uptodate(folio), nr); + folio_put(folio); + return; + } + + if (state == SWAP_PMD_CACHE_EMPTY) { + memset(vec, 0, nr); + return; + } + + /* + * The PMD swap entry is only a compact encoding for consecutive swap + * slots. If the PMD-sized swapcache folio was split, report residency + * from the individual slots covered by this mincore() range. + */ + for (i = 0; i < nr; i++) + vec[i] = mincore_swap(swp_entry(swp_type(entry), + swp_offset(entry) + start + i), + false); +} +#else /* !CONFIG_THP_SWAP */ +static void mincore_pmd_swap(swp_entry_t entry, unsigned long addr, + unsigned long end, unsigned char *vec) +{ + /* Nothing produces PMD swap entries without CONFIG_THP_SWAP. */ + memset(vec, 0, (end - addr) >> PAGE_SHIFT); +} +#endif /* CONFIG_THP_SWAP */ + /* * Later we can get more picky about what "in core" means precisely. * For now, simply check to see if the page is in the page cache, @@ -171,7 +213,10 @@ static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, ptl = pmd_trans_huge_lock(pmd, vma); if (ptl) { - memset(vec, 1, nr); + if (pmd_is_swap_entry(*pmd)) + mincore_pmd_swap(softleaf_from_pmd(*pmd), addr, end, vec); + else + memset(vec, 1, nr); spin_unlock(ptl); goto out; } -- 2.53.0-Meta