From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 0DD292194EB7A for ; Wed, 21 Aug 2019 10:58:49 -0700 (PDT) From: Vivek Goyal Subject: [PATCH 16/19] dax: Create a range version of dax_layout_busy_page() Date: Wed, 21 Aug 2019 13:57:17 -0400 Message-Id: <20190821175720.25901-17-vgoyal@redhat.com> In-Reply-To: <20190821175720.25901-1-vgoyal@redhat.com> References: <20190821175720.25901-1-vgoyal@redhat.com> MIME-Version: 1.0 List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-nvdimm-bounces@lists.01.org Sender: "Linux-nvdimm" To: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org Cc: miklos@szeredi.hu, dgilbert@redhat.com, virtio-fs@redhat.com, stefanha@redhat.com List-ID: While reclaiming a dax range, we do not want to unamap whole file instead want to make sure pages in a certain range do not have references taken on them. Hence create a version of the function which allows to pass in a range. Cc: Dan Williams Signed-off-by: Vivek Goyal --- fs/dax.c | 66 ++++++++++++++++++++++++++++++++------------- include/linux/dax.h | 6 +++++ 2 files changed, 54 insertions(+), 18 deletions(-) diff --git a/fs/dax.c b/fs/dax.c index 60620a37030c..435f5b67e828 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -557,27 +557,20 @@ static void *grab_mapping_entry(struct xa_state *xas, return xa_mk_internal(VM_FAULT_FALLBACK); } -/** - * dax_layout_busy_page - find first pinned page in @mapping - * @mapping: address space to scan for a page with ref count > 1 - * - * DAX requires ZONE_DEVICE mapped pages. These pages are never - * 'onlined' to the page allocator so they are considered idle when - * page->count == 1. A filesystem uses this interface to determine if - * any page in the mapping is busy, i.e. for DMA, or other - * get_user_pages() usages. - * - * It is expected that the filesystem is holding locks to block the - * establishment of new mappings in this address_space. I.e. it expects - * to be able to run unmap_mapping_range() and subsequently not race - * mapping_mapped() becoming true. +/* + * Partial pages are included. If end is 0, pages in the range from start + * to end of the file are inluded. */ -struct page *dax_layout_busy_page(struct address_space *mapping) +struct page *dax_layout_busy_page_range(struct address_space *mapping, + loff_t start, loff_t end) { - XA_STATE(xas, &mapping->i_pages, 0); void *entry; unsigned int scanned = 0; struct page *page = NULL; + pgoff_t start_idx = start >> PAGE_SHIFT; + pgoff_t end_idx = end >> PAGE_SHIFT; + XA_STATE(xas, &mapping->i_pages, start_idx); + loff_t len, lstart = round_down(start, PAGE_SIZE); /* * In the 'limited' case get_user_pages() for dax is disabled. @@ -588,6 +581,22 @@ struct page *dax_layout_busy_page(struct address_space *mapping) if (!dax_mapping(mapping) || !mapping_mapped(mapping)) return NULL; + /* If end == 0, all pages from start to till end of file */ + if (!end) { + end_idx = ULONG_MAX; + len = 0; + } else { + /* length is being calculated from lstart and not start. + * This is due to behavior of unmap_mapping_range(). If + * start is say 4094 and end is on 4093 then want to + * unamp two pages, idx 0 and 1. But unmap_mapping_range() + * will unmap only page at idx 0. If we calculate len + * from the rounded down start, this problem should not + * happen. + */ + len = end - lstart + 1; + } + /* * If we race get_user_pages_fast() here either we'll see the * elevated page count in the iteration and wait, or @@ -600,10 +609,10 @@ struct page *dax_layout_busy_page(struct address_space *mapping) * guaranteed to either see new references or prevent new * references from being established. */ - unmap_mapping_range(mapping, 0, 0, 0); + unmap_mapping_range(mapping, start, len, 0); xas_lock_irq(&xas); - xas_for_each(&xas, entry, ULONG_MAX) { + xas_for_each(&xas, entry, end_idx) { if (WARN_ON_ONCE(!xa_is_value(entry))) continue; if (unlikely(dax_is_locked(entry))) @@ -624,6 +633,27 @@ struct page *dax_layout_busy_page(struct address_space *mapping) xas_unlock_irq(&xas); return page; } +EXPORT_SYMBOL_GPL(dax_layout_busy_page_range); + +/** + * dax_layout_busy_page - find first pinned page in @mapping + * @mapping: address space to scan for a page with ref count > 1 + * + * DAX requires ZONE_DEVICE mapped pages. These pages are never + * 'onlined' to the page allocator so they are considered idle when + * page->count == 1. A filesystem uses this interface to determine if + * any page in the mapping is busy, i.e. for DMA, or other + * get_user_pages() usages. + * + * It is expected that the filesystem is holding locks to block the + * establishment of new mappings in this address_space. I.e. it expects + * to be able to run unmap_mapping_range() and subsequently not race + * mapping_mapped() becoming true. + */ +struct page *dax_layout_busy_page(struct address_space *mapping) +{ + return dax_layout_busy_page_range(mapping, 0, 0); +} EXPORT_SYMBOL_GPL(dax_layout_busy_page); static int __dax_invalidate_entry(struct address_space *mapping, diff --git a/include/linux/dax.h b/include/linux/dax.h index e7f40108f2c9..3ef6686c080b 100644 --- a/include/linux/dax.h +++ b/include/linux/dax.h @@ -145,6 +145,7 @@ int dax_writeback_mapping_range(struct address_space *mapping, struct writeback_control *wbc); struct page *dax_layout_busy_page(struct address_space *mapping); +struct page *dax_layout_busy_page_range(struct address_space *mapping, loff_t start, loff_t end); dax_entry_t dax_lock_page(struct page *page); void dax_unlock_page(struct page *page, dax_entry_t cookie); #else @@ -180,6 +181,11 @@ static inline struct page *dax_layout_busy_page(struct address_space *mapping) return NULL; } +static inline struct page *dax_layout_busy_page_range(struct address_space *mapping, pgoff_t start, pgoff_t nr_pages) +{ + return NULL; +} + static inline int dax_writeback_mapping_range(struct address_space *mapping, struct block_device *bdev, struct dax_device *dax_dev, struct writeback_control *wbc) -- 2.20.1 _______________________________________________ Linux-nvdimm mailing list Linux-nvdimm@lists.01.org https://lists.01.org/mailman/listinfo/linux-nvdimm