From: Jan Kara Subject: Re: [PATCH 2/2] ext4: handle layout changes to pinned DAX mappings Date: Fri, 22 Jun 2018 10:19:15 +0200 Message-ID: <20180622081915.dvqd5sxx7vzoijw3@quack2.suse.cz> References: <20180620221503.25237-1-ross.zwisler@linux.intel.com> <20180620221503.25237-3-ross.zwisler@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Jan Kara , linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org, Dave Chinner , linux-ext4-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Christoph Hellwig To: Ross Zwisler Return-path: Content-Disposition: inline In-Reply-To: <20180620221503.25237-3-ross.zwisler-VuQAYsv1563Yd54FQh9/CA@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-nvdimm-bounces-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org Sender: "Linux-nvdimm" List-Id: linux-ext4.vger.kernel.org On Wed 20-06-18 16:15:03, Ross Zwisler wrote: > Follow the lead of xfs_break_dax_layouts() and add synchronization between > operations in ext4 which remove blocks from an inode (hole punch, truncate > down, etc.) and pages which are pinned due to DAX DMA operations. > > Signed-off-by: Ross Zwisler > --- > fs/ext4/ext4.h | 1 + > fs/ext4/extents.c | 12 ++++++++++++ > fs/ext4/inode.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++ > fs/ext4/truncate.h | 1 + > 4 files changed, 62 insertions(+) > > diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h > index 0b127853c584..34bccd64d83d 100644 > --- a/fs/ext4/ext4.h > +++ b/fs/ext4/ext4.h > @@ -2460,6 +2460,7 @@ extern int ext4_get_inode_loc(struct inode *, struct ext4_iloc *); > extern int ext4_inode_attach_jinode(struct inode *inode); > extern int ext4_can_truncate(struct inode *inode); > extern int ext4_truncate(struct inode *); > +extern int ext4_break_layouts(struct inode *); > extern int ext4_punch_hole(struct inode *inode, loff_t offset, loff_t length); > extern int ext4_truncate_restart_trans(handle_t *, struct inode *, int nblocks); > extern void ext4_set_inode_flags(struct inode *); > diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c > index 0057fe3f248d..a6aef06f455b 100644 > --- a/fs/ext4/extents.c > +++ b/fs/ext4/extents.c > @@ -4820,6 +4820,13 @@ static long ext4_zero_range(struct file *file, loff_t offset, > * released from page cache. > */ > down_write(&EXT4_I(inode)->i_mmap_sem); > + > + ret = ext4_break_layouts(inode); > + if (ret) { > + up_write(&EXT4_I(inode)->i_mmap_sem); > + goto out_mutex; > + } > + > ret = ext4_update_disksize_before_punch(inode, offset, len); > if (ret) { > up_write(&EXT4_I(inode)->i_mmap_sem); > @@ -5493,6 +5500,11 @@ int ext4_collapse_range(struct inode *inode, loff_t offset, loff_t len) > * page cache. > */ > down_write(&EXT4_I(inode)->i_mmap_sem); > + > + ret = ext4_break_layouts(inode); > + if (ret) > + goto out_mmap; > + > /* > * Need to round down offset to be aligned with page size boundary > * for page size > block size. > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c > index 2ea07efbe016..c795e5118745 100644 > --- a/fs/ext4/inode.c > +++ b/fs/ext4/inode.c > @@ -4193,6 +4193,41 @@ int ext4_update_disksize_before_punch(struct inode *inode, loff_t offset, > return 0; > } > > +static void ext4_wait_dax_page(struct ext4_inode_info *ei, bool *did_unlock) > +{ > + *did_unlock = true; > + up_write(&ei->i_mmap_sem); > + schedule(); > + down_write(&ei->i_mmap_sem); > +} > + > +int ext4_break_layouts(struct inode *inode) > +{ > + struct ext4_inode_info *ei = EXT4_I(inode); > + struct page *page; > + bool retry; > + int error; > + > + if (unlikely(!rwsem_is_locked(&ei->i_mmap_sem))) { > + WARN_ON_ONCE(1); > + return -EINVAL; > + } This could be shortened as: if (WARN_ON_ONCE(!rwsem_is_locked(&ei->i_mmap_sem))) { } couldn't it? Besides that the patch looks to me. You can add: Reviewed-by: Jan Kara And I'm really wondering which protection are we still missing that you are still able to hit the warning with these patches applied. Honza -- Jan Kara SUSE Labs, CR