Re: [PATCH 1/4] writeback: Protect inode->i_io_list with inode->i_lock

[Martijn Coenen <maco@android.com>]

Hi Jan,

On Thu, Jun 11, 2020 at 10:12 AM Jan Kara <jack@suse.cz> wrote:
>
> Currently, operations on inode->i_io_list are protected by
> wb->list_lock. In the following patches we'll need to maintain
> consistency between inode->i_state and inode->i_io_list so change the
> code so that inode->i_lock protects also all inode's i_io_list handling.
>
> Signed-off-by: Jan Kara <jack@suse.cz>

LGTM.

Reviewed-by: Martijn Coenen <maco@android.com>

> ---
>  fs/fs-writeback.c | 22 +++++++++++++++++-----
>  1 file changed, 17 insertions(+), 5 deletions(-)
>
> diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
> index a605c3dddabc..ff0b18331590 100644
> --- a/fs/fs-writeback.c
> +++ b/fs/fs-writeback.c
> @@ -144,6 +144,7 @@ static void inode_io_list_del_locked(struct inode *inode,
>                                      struct bdi_writeback *wb)
>  {
>         assert_spin_locked(&wb->list_lock);
> +       assert_spin_locked(&inode->i_lock);
>
>         list_del_init(&inode->i_io_list);
>         wb_io_lists_depopulated(wb);
> @@ -1122,7 +1123,9 @@ void inode_io_list_del(struct inode *inode)
>         struct bdi_writeback *wb;
>
>         wb = inode_to_wb_and_lock_list(inode);
> +       spin_lock(&inode->i_lock);
>         inode_io_list_del_locked(inode, wb);
> +       spin_unlock(&inode->i_lock);
>         spin_unlock(&wb->list_lock);
>  }
>  EXPORT_SYMBOL(inode_io_list_del);
> @@ -1172,8 +1175,10 @@ void sb_clear_inode_writeback(struct inode *inode)
>   * the case then the inode must have been redirtied while it was being written
>   * out and we don't reset its dirtied_when.
>   */
> -static void redirty_tail(struct inode *inode, struct bdi_writeback *wb)
> +static void redirty_tail_locked(struct inode *inode, struct bdi_writeback *wb)
>  {
> +       assert_spin_locked(&inode->i_lock);
> +
>         if (!list_empty(&wb->b_dirty)) {
>                 struct inode *tail;
>
> @@ -1184,6 +1189,13 @@ static void redirty_tail(struct inode *inode, struct bdi_writeback *wb)
>         inode_io_list_move_locked(inode, wb, &wb->b_dirty);
>  }
>
> +static void redirty_tail(struct inode *inode, struct bdi_writeback *wb)
> +{
> +       spin_lock(&inode->i_lock);
> +       redirty_tail_locked(inode, wb);
> +       spin_unlock(&inode->i_lock);
> +}
> +
>  /*
>   * requeue inode for re-scanning after bdi->b_io list is exhausted.
>   */
> @@ -1394,7 +1406,7 @@ static void requeue_inode(struct inode *inode, struct bdi_writeback *wb,
>                  * writeback is not making progress due to locked
>                  * buffers. Skip this inode for now.
>                  */
> -               redirty_tail(inode, wb);
> +               redirty_tail_locked(inode, wb);
>                 return;
>         }
>
> @@ -1414,7 +1426,7 @@ static void requeue_inode(struct inode *inode, struct bdi_writeback *wb,
>                          * retrying writeback of the dirty page/inode
>                          * that cannot be performed immediately.
>                          */
> -                       redirty_tail(inode, wb);
> +                       redirty_tail_locked(inode, wb);
>                 }
>         } else if (inode->i_state & I_DIRTY) {
>                 /*
> @@ -1422,7 +1434,7 @@ static void requeue_inode(struct inode *inode, struct bdi_writeback *wb,
>                  * such as delayed allocation during submission or metadata
>                  * updates after data IO completion.
>                  */
> -               redirty_tail(inode, wb);
> +               redirty_tail_locked(inode, wb);
>         } else if (inode->i_state & I_DIRTY_TIME) {
>                 inode->dirtied_when = jiffies;
>                 inode_io_list_move_locked(inode, wb, &wb->b_dirty_time);
> @@ -1669,8 +1681,8 @@ static long writeback_sb_inodes(struct super_block *sb,
>                  */
>                 spin_lock(&inode->i_lock);
>                 if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) {
> +                       redirty_tail_locked(inode, wb);
>                         spin_unlock(&inode->i_lock);
> -                       redirty_tail(inode, wb);
>                         continue;
>                 }
>                 if ((inode->i_state & I_SYNC) && wbc.sync_mode != WB_SYNC_ALL) {
> --
> 2.16.4
>