Re: [PATCH 3.2 39/79] ocfs2: should wait dio before inode lock in ocfs2_setattr()

[alex chen]

Hi Ben,

ocfs2_dio_end_io_write() was introduced in 4.6 and the problem this patch
fixes is only exist in the kernel 4.6 and above 4.6.

Thanks,
Alex

On 2018/2/11 12:20, Ben Hutchings wrote:
> 3.2.99-rc1 review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: alex chen <alex.chen@xxxxxxxxxx>
> 
> commit 28f5a8a7c033cbf3e32277f4cc9c6afd74f05300 upstream.
> 
> we should wait dio requests to finish before inode lock in
> ocfs2_setattr(), otherwise the following deadlock will happen:
> 
> process 1                  process 2                    process 3
> truncate file 'A'          end_io of writing file 'A'   receiving the bast messages
> ocfs2_setattr
>  ocfs2_inode_lock_tracker
>   ocfs2_inode_lock_full
>  inode_dio_wait
>   __inode_dio_wait
>   -->waiting for all dio
>   requests finish
>                                                         dlm_proxy_ast_handler
>                                                          dlm_do_local_bast
>                                                           ocfs2_blocking_ast
>                                                            ocfs2_generic_handle_bast
>                                                             set OCFS2_LOCK_BLOCKED flag
>                         dio_end_io
>                          dio_bio_end_aio
>                           dio_complete
>                            ocfs2_dio_end_io
>                             ocfs2_dio_end_io_write
>                              ocfs2_inode_lock
>                               __ocfs2_cluster_lock
>                                ocfs2_wait_for_mask
>                                -->waiting for OCFS2_LOCK_BLOCKED
>                                flag to be cleared, that is waiting
>                                for 'process 1' unlocking the inode lock
>                            inode_dio_end
>                            -->here dec the i_dio_count, but will never
>                            be called, so a deadlock happened.
> 
> Link: http://lkml.kernel.org/r/59F81636.70508@xxxxxxxxxx
> Signed-off-by: Alex Chen <alex.chen@xxxxxxxxxx>
> Reviewed-by: Jun Piao <piaojun@xxxxxxxxxx>
> Reviewed-by: Joseph Qi <jiangqi903@xxxxxxxxx>
> Acked-by: Changwei Ge <ge.changwei@xxxxxxx>
> Cc: Mark Fasheh <mfasheh@xxxxxxxxxxx>
> Cc: Joel Becker <jlbec@xxxxxxxxxxxx>
> Cc: Junxiao Bi <junxiao.bi@xxxxxxxxxx>
> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
> ---
>  fs/ocfs2/file.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> --- a/fs/ocfs2/file.c
> +++ b/fs/ocfs2/file.c
> @@ -1130,6 +1130,13 @@ int ocfs2_setattr(struct dentry *dentry,
>  		dquot_initialize(inode);
>  	size_change = S_ISREG(inode->i_mode) && attr->ia_valid & ATTR_SIZE;
>  	if (size_change) {
> +		/*
> +		 * Here we should wait dio to finish before inode lock
> +		 * to avoid a deadlock between ocfs2_setattr() and
> +		 * ocfs2_dio_end_io_write()
> +		 */
> +		inode_dio_wait(inode);
> +
>  		status = ocfs2_rw_lock(inode, 1);
>  		if (status < 0) {
>  			mlog_errno(status);
> @@ -1149,8 +1156,6 @@ int ocfs2_setattr(struct dentry *dentry,
>  		if (status)
>  			goto bail_unlock;
>  
> -		inode_dio_wait(inode);
> -
>  		if (i_size_read(inode) >= attr->ia_size) {
>  			if (ocfs2_should_order_data(inode)) {
>  				status = ocfs2_begin_ordered_truncate(inode,
> 
> 
> .
>