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?
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.
Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
