From nobody Wed Dec 17 08:54:48 2025 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 EDA56149E15 for ; Thu, 11 Jul 2024 10:49:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720694976; cv=none; b=ouM6adM9yRHbgx8T7EXbivghs0qAWmtU0olOIofvtnjjOqXyu/Jnndy5wOTk9tWnATTLmEhkAhfuVXI9SsXV4CcNxa4qSETjPEd/pIDnY2ipYqQ5AwkIxJJqdrO/N0pZKYGC00ModO+k5dhvPStHTZJHWZXT7CwhOWtFHJ2btqA= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720694976; c=relaxed/simple; bh=XXVKLrd1IMiPrtBxjlRxfKvg4Oil4eY2nBwgOKodzTA=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=qrkaO+rztauaRm+0JWM7aR9QCs3iQLRFdTMajI0eFGrjNddhQLxrAKpnI/WIZbk7gr3vUSjEbI5MMxrt9DA0YWnx4ktDvmGiF58guH1nn9jSe2s/T7x9FOu6VznBmdrraBZW4+3xtGnZ41uaNorphMk6AjJuuThbipXxg+49Nwc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=Kv6iTVF3; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Kv6iTVF3" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1720694973; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=tZC3wpUX2uGzu3svYpunH5/qYl9NuP85eye8VqVTeVk=; b=Kv6iTVF3gh2Zzr1/yv5JTfu2xKrJRomDr97Y05gNHqftXrdqGyqizE8S8dSuuqQ7kTVFwl /Z4pQggqeDxMfiXaSh2rCMUp+bNhAPoE/cBJSA623081oHqy78qkSrp6QBWLtIrMHWGkw5 AhCxk037b6vJusaN258NCs3UP6o9mBI= Received: from mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-18-xS58UjoBPoWgHtVH316iHA-1; Thu, 11 Jul 2024 06:49:27 -0400 X-MC-Unique: xS58UjoBPoWgHtVH316iHA-1 Received: from mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.40]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 914F719560B9; Thu, 11 Jul 2024 10:49:25 +0000 (UTC) Received: from gshan-thinkpadx1nanogen2.remote.csb (unknown [10.64.136.68]) by mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 5A72A19560AA; Thu, 11 Jul 2024 10:49:20 +0000 (UTC) From: Gavin Shan To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, akpm@linux-foundation.org, william.kucharski@oracle.com, willy@infradead.org, david@redhat.com, ryan.roberts@arm.com, shan.gavin@gmail.com Subject: [PATCH] mm/huge_memory: Avoid PMD-size page cache if needed Date: Thu, 11 Jul 2024 20:48:40 +1000 Message-ID: <20240711104840.200573-1-gshan@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.40 Content-Type: text/plain; charset="utf-8" Currently, xarray can't support arbitrary page cache size and the largest and supported page cache size is defined as MAX_PAGECACHE_ORDER in commit 099d90642a71 ("mm/filemap: make MAX_PAGECACHE_ORDER acceptable to xarray"). However, it's possible to have 512MB page cache in the huge memory collapsing path on ARM64 system whose base page size is 64KB. A warning is raised when the huge page cache is split as shown in the following example. [root@dhcp-10-26-1-207 ~]# cat /proc/1/smaps | grep KernelPageSize KernelPageSize: 64 kB [root@dhcp-10-26-1-207 ~]# cat /tmp/test.c : int main(int argc, char **argv) { const char *filename =3D TEST_XFS_FILENAME; int fd =3D 0; void *buf =3D (void *)-1, *p; int pgsize =3D getpagesize(); int ret =3D 0; if (pgsize !=3D 0x10000) { fprintf(stdout, "System with 64KB base page size is required!\n"); return -EPERM; } system("echo 0 > /sys/devices/virtual/bdi/253:0/read_ahead_kb"); system("echo 1 > /proc/sys/vm/drop_caches"); /* Open xfs or shmem file */ fd =3D open(filename, O_RDONLY); assert(fd > 0); /* Create VMA */ buf =3D mmap(NULL, TEST_MEM_SIZE, PROT_READ, MAP_SHARED, fd, 0); assert(buf !=3D (void *)-1); fprintf(stdout, "mapped buffer at 0x%p\n", buf); /* Populate VMA */ ret =3D madvise(buf, TEST_MEM_SIZE, MADV_NOHUGEPAGE); assert(ret =3D=3D 0); ret =3D madvise(buf, TEST_MEM_SIZE, MADV_POPULATE_READ); assert(ret =3D=3D 0); /* Collapse VMA */ ret =3D madvise(buf, TEST_MEM_SIZE, MADV_HUGEPAGE); assert(ret =3D=3D 0); ret =3D madvise(buf, TEST_MEM_SIZE, MADV_COLLAPSE); if (ret) { fprintf(stdout, "Error %d to madvise(MADV_COLLAPSE)\n", errno); goto out; } /* Split xarray. The file needs to reopened with write permission */ munmap(buf, TEST_MEM_SIZE); buf =3D (void *)-1; close(fd); fd =3D open(filename, O_RDWR); assert(fd > 0); fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE, TEST_MEM_SIZE - pgsize, pgsize); out: if (buf !=3D (void *)-1) munmap(buf, TEST_MEM_SIZE); if (fd > 0) close(fd); return ret; } [root@dhcp-10-26-1-207 ~]# gcc /tmp/test.c -o /tmp/test [root@dhcp-10-26-1-207 ~]# /tmp/test ------------[ cut here ]------------ WARNING: CPU: 25 PID: 7560 at lib/xarray.c:1025 xas_split_alloc+0xf8/0x128 Modules linked in: nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib \ nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct \ nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 \ ip_set rfkill nf_tables nfnetlink vfat fat virtio_balloon drm fuse \ xfs libcrc32c crct10dif_ce ghash_ce sha2_ce sha256_arm64 virtio_net \ sha1_ce net_failover virtio_blk virtio_console failover dimlib virtio_mmio CPU: 25 PID: 7560 Comm: test Kdump: loaded Not tainted 6.10.0-rc7-gavin+ #9 Hardware name: QEMU KVM Virtual Machine, BIOS edk2-20240524-1.el9 05/24/20= 24 pstate: 83400005 (Nzcv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=3D--) pc : xas_split_alloc+0xf8/0x128 lr : split_huge_page_to_list_to_order+0x1c4/0x780 sp : ffff8000ac32f660 x29: ffff8000ac32f660 x28: ffff0000e0969eb0 x27: ffff8000ac32f6c0 x26: 0000000000000c40 x25: ffff0000e0969eb0 x24: 000000000000000d x23: ffff8000ac32f6c0 x22: ffffffdfc0700000 x21: 0000000000000000 x20: 0000000000000000 x19: ffffffdfc0700000 x18: 0000000000000000 x17: 0000000000000000 x16: ffffd5f3708ffc70 x15: 0000000000000000 x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000 x11: ffffffffffffffc0 x10: 0000000000000040 x9 : ffffd5f3708e692c x8 : 0000000000000003 x7 : 0000000000000000 x6 : ffff0000e0969eb8 x5 : ffffd5f37289e378 x4 : 0000000000000000 x3 : 0000000000000c40 x2 : 000000000000000d x1 : 000000000000000c x0 : 0000000000000000 Call trace: xas_split_alloc+0xf8/0x128 split_huge_page_to_list_to_order+0x1c4/0x780 truncate_inode_partial_folio+0xdc/0x160 truncate_inode_pages_range+0x1b4/0x4a8 truncate_pagecache_range+0x84/0xa0 xfs_flush_unmap_range+0x70/0x90 [xfs] xfs_file_fallocate+0xfc/0x4d8 [xfs] vfs_fallocate+0x124/0x2f0 ksys_fallocate+0x4c/0xa0 __arm64_sys_fallocate+0x24/0x38 invoke_syscall.constprop.0+0x7c/0xd8 do_el0_svc+0xb4/0xd0 el0_svc+0x44/0x1d8 el0t_64_sync_handler+0x134/0x150 el0t_64_sync+0x17c/0x180 Fix it by avoiding PMD-sized page cache in the huge memory collapsing path. After this patch is applied, the test program fails with error -EINVAL returned from __thp_vma_allowable_orders() and the madvise() system call to collapse the page caches. Fixes: 6b24ca4a1a8d ("mm: Use multi-index entries in the page cache") Cc: # v5.17+ Signed-off-by: Gavin Shan --- mm/huge_memory.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 2120f7478e55..e9335ac667be 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -136,7 +136,8 @@ unsigned long __thp_vma_allowable_orders(struct vm_area= _struct *vma, =20 while (orders) { addr =3D vma->vm_end - (PAGE_SIZE << order); - if (thp_vma_suitable_order(vma, addr, order)) + if (!(vma->vm_file && order > MAX_PAGECACHE_ORDER) && + thp_vma_suitable_order(vma, addr, order)) break; order =3D next_order(&orders, order); } --=20 2.45.2