From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f69.google.com (mail-wm0-f69.google.com [74.125.82.69]) by kanga.kvack.org (Postfix) with ESMTP id 85E6F280295 for ; Tue, 27 Sep 2016 12:16:11 -0400 (EDT) Received: by mail-wm0-f69.google.com with SMTP id l138so13206336wmg.3 for ; Tue, 27 Sep 2016 09:16:11 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id f127si10059123wmf.105.2016.09.27.09.08.34 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 27 Sep 2016 09:08:34 -0700 (PDT) From: Jan Kara Subject: [PATCH 19/20] dax: Protect PTE modification on WP fault by radix tree entry lock Date: Tue, 27 Sep 2016 18:08:23 +0200 Message-Id: <1474992504-20133-20-git-send-email-jack@suse.cz> In-Reply-To: <1474992504-20133-1-git-send-email-jack@suse.cz> References: <1474992504-20133-1-git-send-email-jack@suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: linux-mm@kvack.org Cc: linux-fsdevel@vger.kernel.org, linux-nvdimm@lists.01.org, Dan Williams , Ross Zwisler , "Kirill A. Shutemov" , Jan Kara Currently PTE gets updated in wp_pfn_shared() after dax_pfn_mkwrite() has released corresponding radix tree entry lock. When we want to writeprotect PTE on cache flush, we need PTE modification to happen under radix tree entry lock to ensure consisten updates of PTE and radix tree (standard faults use page lock to ensure this consistency). So move update of PTE bit into dax_pfn_mkwrite(). Signed-off-by: Jan Kara --- fs/dax.c | 22 ++++++++++++++++------ mm/memory.c | 2 +- 2 files changed, 17 insertions(+), 7 deletions(-) diff --git a/fs/dax.c b/fs/dax.c index c6cadf8413a3..a2d3781c9f4e 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -1163,17 +1163,27 @@ int dax_pfn_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf) { struct file *file = vma->vm_file; struct address_space *mapping = file->f_mapping; - void *entry; + void *entry, **slot; pgoff_t index = vmf->pgoff; spin_lock_irq(&mapping->tree_lock); - entry = get_unlocked_mapping_entry(mapping, index, NULL); - if (!entry || !radix_tree_exceptional_entry(entry)) - goto out; + entry = get_unlocked_mapping_entry(mapping, index, &slot); + if (!entry || !radix_tree_exceptional_entry(entry)) { + if (entry) + put_unlocked_mapping_entry(mapping, index, entry); + spin_unlock_irq(&mapping->tree_lock); + return VM_FAULT_NOPAGE; + } radix_tree_tag_set(&mapping->page_tree, index, PAGECACHE_TAG_DIRTY); - put_unlocked_mapping_entry(mapping, index, entry); -out: + entry = lock_slot(mapping, slot); spin_unlock_irq(&mapping->tree_lock); + /* + * If we race with somebody updating the PTE and finish_mkwrite_fault() + * fails, we don't care. We need to return VM_FAULT_NOPAGE and retry + * the fault in either case. + */ + finish_mkwrite_fault(vmf); + put_locked_mapping_entry(mapping, index, entry); return VM_FAULT_NOPAGE; } EXPORT_SYMBOL_GPL(dax_pfn_mkwrite); diff --git a/mm/memory.c b/mm/memory.c index e7a4a30a5e88..5fa3d0c5196e 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2310,7 +2310,7 @@ static int wp_pfn_shared(struct vm_fault *vmf) pte_unmap_unlock(vmf->pte, vmf->ptl); vmf->flags |= FAULT_FLAG_MKWRITE; ret = vma->vm_ops->pfn_mkwrite(vma, vmf); - if (ret & VM_FAULT_ERROR) + if (ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)) return ret; return finish_mkwrite_fault(vmf); } -- 2.6.6 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org