On Fri, Jun 22, 2018 at 10:19:15AM +0200, Jan Kara wrote:
> 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 <ross.zwisler@xxxxxxxxxxxxxxx>
> > ---
> > 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?
Yep, that's much better. Thank you for the review.
> Besides that the patch looks to me. You can add:
>
> Reviewed-by: Jan Kara <jack@xxxxxxx>
>
> And I'm really wondering which protection are we still missing that you are
> still able to hit the warning with these patches applied.
I'm also very curious and am going to dig into that this week.
