From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga18.intel.com ([134.134.136.126]:41404 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754371AbeCUXHi (ORCPT ); Wed, 21 Mar 2018 19:07:38 -0400 Subject: [PATCH v7 14/14] xfs, dax: introduce xfs_break_dax_layouts() From: Dan Williams To: linux-nvdimm@lists.01.org Cc: Jan Kara , Dave Chinner , "Darrick J. Wong" , Ross Zwisler , Christoph Hellwig , linux-fsdevel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-kernel@vger.kernel.org, jack@suse.cz Date: Wed, 21 Mar 2018 15:58:31 -0700 Message-ID: <152167311132.5268.8502709708606276650.stgit@dwillia2-desk3.amr.corp.intel.com> In-Reply-To: <152167302988.5268.4370226749268662682.stgit@dwillia2-desk3.amr.corp.intel.com> References: <152167302988.5268.4370226749268662682.stgit@dwillia2-desk3.amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-fsdevel-owner@vger.kernel.org List-ID: xfs_break_dax_layouts(), similar to xfs_break_leased_layouts(), scans for busy / pinned dax pages and waits for those pages to go idle before any potential extent unmap operation. dax_layout_busy_page() handles synchronizing against new page-busy events (get_user_pages). It invalidates all mappings to trigger the get_user_pages slow path which will eventually block on the xfs inode lock held in XFS_MMAPLOCK_EXCL mode. If dax_layout_busy_page() finds a busy page it returns it for xfs to wait for the page-idle event that will fire when the page reference count reaches 1 (recall ZONE_DEVICE pages are idle at count 1, see generic_dax_pagefree()). While waiting, the XFS_MMAPLOCK_EXCL lock is dropped in order to not deadlock the process that might be trying to elevate the page count of more pages before arranging for any of them to go idle. I.e. the typical case of submitting I/O is that iov_iter_get_pages() elevates the reference count of all pages in the I/O before starting I/O on the first page. The process of elevating the reference count of all pages involved in an I/O may cause faults that need to take XFS_MMAPLOCK_EXCL. Cc: Jan Kara Cc: Dave Chinner Cc: "Darrick J. Wong" Cc: Ross Zwisler Reviewed-by: Christoph Hellwig Signed-off-by: Dan Williams --- fs/xfs/xfs_file.c | 59 ++++++++++++++++++++++++++++++++++++++++++++--------- 1 file changed, 49 insertions(+), 10 deletions(-) diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c index 7f37fadf007e..d4573f93fddb 100644 --- a/fs/xfs/xfs_file.c +++ b/fs/xfs/xfs_file.c @@ -752,6 +752,38 @@ xfs_file_write_iter( return ret; } +static void +xfs_wait_var_event( + struct inode *inode, + uint iolock, + bool *did_unlock) +{ + struct xfs_inode *ip = XFS_I(inode); + + *did_unlock = true; + xfs_iunlock(ip, iolock); + schedule(); + xfs_ilock(ip, iolock); +} + +static int +xfs_break_dax_layouts( + struct inode *inode, + uint iolock, + bool *did_unlock) +{ + struct page *page; + + *did_unlock = false; + page = dax_layout_busy_page(inode->i_mapping); + if (!page) + return 0; + + return ___wait_var_event(&page->_refcount, + atomic_read(&page->_refcount) == 1, TASK_INTERRUPTIBLE, + 0, 0, xfs_wait_var_event(inode, iolock, did_unlock)); +} + int xfs_break_layouts( struct inode *inode, @@ -766,16 +798,23 @@ xfs_break_layouts( | (reason == BREAK_UNMAPI ? XFS_MMAPLOCK_EXCL : 0))); - switch (reason) { - case BREAK_UNMAPI: - /* fall through */ - case BREAK_WRITE: - error = xfs_break_leased_layouts(inode, iolock, &did_unlock); - break; - default: - error = -EINVAL; - break; - } + do { + switch (reason) { + case BREAK_UNMAPI: + error = xfs_break_dax_layouts(inode, *iolock, + &did_unlock); + /* fall through */ + case BREAK_WRITE: + if (error || did_unlock) + break; + error = xfs_break_leased_layouts(inode, iolock, + &did_unlock); + break; + default: + error = -EINVAL; + break; + } + } while (error == 0 && did_unlock); return error; }