From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S967775AbcA1NQf (ORCPT ); Thu, 28 Jan 2016 08:16:35 -0500 Received: from mx2.suse.de ([195.135.220.15]:49822 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751496AbcA1NQY (ORCPT ); Thu, 28 Jan 2016 08:16:24 -0500 Date: Thu, 28 Jan 2016 14:16:30 +0100 From: Jan Kara To: Ross Zwisler Cc: linux-kernel@vger.kernel.org, "Theodore Ts'o" , Dan Williams , Jan Kara , Matthew Wilcox , linux-ext4@vger.kernel.org, linux-nvdimm@ml01.01.org Subject: Re: [PATCH] ext2, ext4: Fix issue with missing journal entry Message-ID: <20160128131630.GI7726@quack.suse.cz> References: <1453921308-5544-1-git-send-email-ross.zwisler@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1453921308-5544-1-git-send-email-ross.zwisler@linux.intel.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 27-01-16 12:01:48, Ross Zwisler wrote: > As it is currently written ext4_dax_mkwrite() assumes that the call into > __dax_mkwrite() will not have to do a block allocation so it doesn't create > a journal entry. For a read that creates a zero page to cover a hole > followed by a write that actually allocates storage this is incorrect. The > ext4_dax_mkwrite() -> __dax_mkwrite() -> __dax_fault() path calls > get_blocks() to allocate storage. > > Fix this by having the ->page_mkwrite fault handler call ext4_dax_fault() > as this function already has all the logic needed to allocate a journal > entry and call __dax_fault(). > > Also update the ext2 fault handlers in this same way to remove duplicate > code and keep the logic between ext2 and ext4 the same. > > Signed-off-by: Ross Zwisler Ah, ok, you are right. The patch looks good but Matthew is reworking the area more (so ext4_da_mkwrite() is likely to return) so it this worth it? Or do you expect Matthew's patches to land much later? Honza > --- > fs/ext2/file.c | 19 +------------------ > fs/ext4/file.c | 19 ++----------------- > 2 files changed, 3 insertions(+), 35 deletions(-) > > diff --git a/fs/ext2/file.c b/fs/ext2/file.c > index 2c88d68..c1400b1 100644 > --- a/fs/ext2/file.c > +++ b/fs/ext2/file.c > @@ -80,23 +80,6 @@ static int ext2_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr, > return ret; > } > > -static int ext2_dax_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf) > -{ > - struct inode *inode = file_inode(vma->vm_file); > - struct ext2_inode_info *ei = EXT2_I(inode); > - int ret; > - > - sb_start_pagefault(inode->i_sb); > - file_update_time(vma->vm_file); > - down_read(&ei->dax_sem); > - > - ret = __dax_mkwrite(vma, vmf, ext2_get_block, NULL); > - > - up_read(&ei->dax_sem); > - sb_end_pagefault(inode->i_sb); > - return ret; > -} > - > static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma, > struct vm_fault *vmf) > { > @@ -124,7 +107,7 @@ static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma, > static const struct vm_operations_struct ext2_dax_vm_ops = { > .fault = ext2_dax_fault, > .pmd_fault = ext2_dax_pmd_fault, > - .page_mkwrite = ext2_dax_mkwrite, > + .page_mkwrite = ext2_dax_fault, > .pfn_mkwrite = ext2_dax_pfn_mkwrite, > }; > > diff --git a/fs/ext4/file.c b/fs/ext4/file.c > index 1126436..d2e8500 100644 > --- a/fs/ext4/file.c > +++ b/fs/ext4/file.c > @@ -262,23 +262,8 @@ static int ext4_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr, > return result; > } > > -static int ext4_dax_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf) > -{ > - int err; > - struct inode *inode = file_inode(vma->vm_file); > - > - sb_start_pagefault(inode->i_sb); > - file_update_time(vma->vm_file); > - down_read(&EXT4_I(inode)->i_mmap_sem); > - err = __dax_mkwrite(vma, vmf, ext4_dax_mmap_get_block, NULL); > - up_read(&EXT4_I(inode)->i_mmap_sem); > - sb_end_pagefault(inode->i_sb); > - > - return err; > -} > - > /* > - * Handle write fault for VM_MIXEDMAP mappings. Similarly to ext4_dax_mkwrite() > + * Handle write fault for VM_MIXEDMAP mappings. Similarly to ext4_dax_fault() > * handler we check for races agaist truncate. Note that since we cycle through > * i_mmap_sem, we are sure that also any hole punching that began before we > * were called is finished by now and so if it included part of the file we > @@ -311,7 +296,7 @@ static int ext4_dax_pfn_mkwrite(struct vm_area_struct *vma, > static const struct vm_operations_struct ext4_dax_vm_ops = { > .fault = ext4_dax_fault, > .pmd_fault = ext4_dax_pmd_fault, > - .page_mkwrite = ext4_dax_mkwrite, > + .page_mkwrite = ext4_dax_fault, > .pfn_mkwrite = ext4_dax_pfn_mkwrite, > }; > #else > -- > 2.5.0 > > -- Jan Kara SUSE Labs, CR