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

alex chen
2018-02-11T07:40:18Z

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@huawei.com>
>
> 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@huawei.com
> Signed-off-by: Alex Chen <alex.chen@huawei.com>
> Reviewed-by: Jun Piao <piaojun@huawei.com>
> Reviewed-by: Joseph Qi <jiangqi903@gmail.com>
> Acked-by: Changwei Ge <ge.changwei@h3c.com>
> Cc: Mark Fasheh <mfasheh@versity.com>
> Cc: Joel Becker <jlbec@evilplan.org>
> Cc: Junxiao Bi <junxiao.bi@oracle.com>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
> ---
> 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,
>
>
> .
>