From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de ([195.135.220.15]:37807 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752847AbcCJTSk (ORCPT ); Thu, 10 Mar 2016 14:18:40 -0500 From: Jan Kara To: linux-fsdevel@vger.kernel.org Cc: "Wilcox, Matthew R" , Ross Zwisler , Dan Williams , linux-nvdimm@lists.01.org, NeilBrown , Jan Kara Subject: [PATCH 05/12] dax: Remove synchronization using i_mmap_lock Date: Thu, 10 Mar 2016 20:18:48 +0100 Message-Id: <1457637535-21633-6-git-send-email-jack@suse.cz> In-Reply-To: <1457637535-21633-1-git-send-email-jack@suse.cz> References: <1457637535-21633-1-git-send-email-jack@suse.cz> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: At one point DAX used i_mmap_lock so synchronize page faults with page table invalidation during truncate. However these days DAX uses filesystem specific RW semaphores to protect against these races (i_mmap_sem in ext2 & ext4 cases, XFS_MMAPLOCK in xfs case). So remove the unnecessary locking. Signed-off-by: Jan Kara --- fs/dax.c | 19 ------------------- mm/memory.c | 14 -------------- 2 files changed, 33 deletions(-) diff --git a/fs/dax.c b/fs/dax.c index 9c4d697fb6fc..e409e8fc13b7 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -563,8 +563,6 @@ static int dax_insert_mapping(struct inode *inode, struct buffer_head *bh, pgoff_t size; int error; - i_mmap_lock_read(mapping); - /* * Check truncate didn't happen while we were allocating a block. * If it did, this block may or may not be still allocated to the @@ -597,8 +595,6 @@ static int dax_insert_mapping(struct inode *inode, struct buffer_head *bh, error = vm_insert_mixed(vma, vaddr, dax.pfn); out: - i_mmap_unlock_read(mapping); - return error; } @@ -695,17 +691,6 @@ int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf, if (error) goto unlock_page; vmf->page = page; - if (!page) { - i_mmap_lock_read(mapping); - /* Check we didn't race with truncate */ - size = (i_size_read(inode) + PAGE_SIZE - 1) >> - PAGE_SHIFT; - if (vmf->pgoff >= size) { - i_mmap_unlock_read(mapping); - error = -EIO; - goto out; - } - } return VM_FAULT_LOCKED; } @@ -895,8 +880,6 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address, truncate_pagecache_range(inode, lstart, lend); } - i_mmap_lock_read(mapping); - /* * If a truncate happened while we were allocating blocks, we may * leave blocks allocated to the file that are beyond EOF. We can't @@ -1013,8 +996,6 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address, } out: - i_mmap_unlock_read(mapping); - if (buffer_unwritten(&bh)) complete_unwritten(&bh, !(result & VM_FAULT_ERROR)); diff --git a/mm/memory.c b/mm/memory.c index 8132787ae4d5..13f76eb08f33 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2430,8 +2430,6 @@ void unmap_mapping_range(struct address_space *mapping, if (details.last_index < details.first_index) details.last_index = ULONG_MAX; - - /* DAX uses i_mmap_lock to serialise file truncate vs page fault */ i_mmap_lock_write(mapping); if (unlikely(!RB_EMPTY_ROOT(&mapping->i_mmap))) unmap_mapping_range_tree(&mapping->i_mmap, &details); @@ -3019,12 +3017,6 @@ static int do_cow_fault(struct mm_struct *mm, struct vm_area_struct *vma, if (fault_page) { unlock_page(fault_page); page_cache_release(fault_page); - } else { - /* - * The fault handler has no page to lock, so it holds - * i_mmap_lock for read to protect against truncate. - */ - i_mmap_unlock_read(vma->vm_file->f_mapping); } goto uncharge_out; } @@ -3035,12 +3027,6 @@ static int do_cow_fault(struct mm_struct *mm, struct vm_area_struct *vma, if (fault_page) { unlock_page(fault_page); page_cache_release(fault_page); - } else { - /* - * The fault handler has no page to lock, so it holds - * i_mmap_lock for read to protect against truncate. - */ - i_mmap_unlock_read(vma->vm_file->f_mapping); } return ret; uncharge_out: -- 2.6.2