Re: [PATCH v4 10/17] xfs: acquire ->ail_lock from xfs_trans_ail_delete()

[Allison Collins <allison.henderson@xxxxxxxxxx>]

On 5/4/20 7:11 AM, Brian Foster wrote:
> Several callers acquire the lock just prior to the call. Callers
> that require ->ail_lock for other purposes already check IN_AIL
> state and thus don't require the additional shutdown check in the
> helper. Push the lock down into xfs_trans_ail_delete(), open code
> the instances that still acquire it, and remove the unnecessary ailp
> parameter.
>
> Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx>
> Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Ok, followed it through and I think it makes sense:
Reviewed-by: Allison Collins <allison.henderson@xxxxxxxxxx>

> ---
>   fs/xfs/xfs_buf_item.c   | 27 +++++++++++----------------
>   fs/xfs/xfs_dquot.c      |  6 ++++--
>   fs/xfs/xfs_trans_ail.c  |  3 ++-
>   fs/xfs/xfs_trans_priv.h | 14 ++++++++------
>   4 files changed, 25 insertions(+), 25 deletions(-)
>
> diff --git a/fs/xfs/xfs_buf_item.c b/fs/xfs/xfs_buf_item.c
> index 1f7acffc99ba..06e306b49283 100644
> --- a/fs/xfs/xfs_buf_item.c
> +++ b/fs/xfs/xfs_buf_item.c
> @@ -410,7 +410,6 @@ xfs_buf_item_unpin(
>   {
>   	struct xfs_buf_log_item	*bip = BUF_ITEM(lip);
>   	xfs_buf_t		*bp = bip->bli_buf;
> -	struct xfs_ail		*ailp = lip->li_ailp;
>   	int			stale = bip->bli_flags & XFS_BLI_STALE;
>   	int			freed;
>   
> @@ -452,10 +451,10 @@ xfs_buf_item_unpin(
>   		}
>   
>   		/*
> -		 * If we get called here because of an IO error, we may
> -		 * or may not have the item on the AIL. xfs_trans_ail_delete()
> -		 * will take care of that situation.
> -		 * xfs_trans_ail_delete() drops the AIL lock.
> +		 * If we get called here because of an IO error, we may or may
> +		 * not have the item on the AIL. xfs_trans_ail_delete() will
> +		 * take care of that situation. xfs_trans_ail_delete() drops
> +		 * the AIL lock.
>   		 */
>   		if (bip->bli_flags & XFS_BLI_STALE_INODE) {
>   			xfs_buf_do_callbacks(bp);
> @@ -463,8 +462,7 @@ xfs_buf_item_unpin(
>   			list_del_init(&bp->b_li_list);
>   			bp->b_iodone = NULL;
>   		} else {
> -			spin_lock(&ailp->ail_lock);
> -			xfs_trans_ail_delete(ailp, lip, SHUTDOWN_LOG_IO_ERROR);
> +			xfs_trans_ail_delete(lip, SHUTDOWN_LOG_IO_ERROR);
>   			xfs_buf_item_relse(bp);
>   			ASSERT(bp->b_log_item == NULL);
>   		}
> @@ -1205,22 +1203,19 @@ xfs_buf_iodone(
>   	struct xfs_buf		*bp,
>   	struct xfs_log_item	*lip)
>   {
> -	struct xfs_ail		*ailp = lip->li_ailp;
> -
>   	ASSERT(BUF_ITEM(lip)->bli_buf == bp);
>   
>   	xfs_buf_rele(bp);
>   
>   	/*
> -	 * If we are forcibly shutting down, this may well be
> -	 * off the AIL already. That's because we simulate the
> -	 * log-committed callbacks to unpin these buffers. Or we may never
> -	 * have put this item on AIL because of the transaction was
> -	 * aborted forcibly. xfs_trans_ail_delete() takes care of these.
> +	 * If we are forcibly shutting down, this may well be off the AIL
> +	 * already. That's because we simulate the log-committed callbacks to
> +	 * unpin these buffers. Or we may never have put this item on AIL
> +	 * because of the transaction was aborted forcibly.
> +	 * xfs_trans_ail_delete() takes care of these.
>   	 *
>   	 * Either way, AIL is useless if we're forcing a shutdown.
>   	 */
> -	spin_lock(&ailp->ail_lock);
> -	xfs_trans_ail_delete(ailp, lip, SHUTDOWN_CORRUPT_INCORE);
> +	xfs_trans_ail_delete(lip, SHUTDOWN_CORRUPT_INCORE);
>   	xfs_buf_item_free(BUF_ITEM(lip));
>   }
> diff --git a/fs/xfs/xfs_dquot.c b/fs/xfs/xfs_dquot.c
> index ffe607733c50..5fb65f43b980 100644
> --- a/fs/xfs/xfs_dquot.c
> +++ b/fs/xfs/xfs_dquot.c
> @@ -1021,6 +1021,7 @@ xfs_qm_dqflush_done(
>   	struct xfs_dq_logitem	*qip = (struct xfs_dq_logitem *)lip;
>   	struct xfs_dquot	*dqp = qip->qli_dquot;
>   	struct xfs_ail		*ailp = lip->li_ailp;
> +	xfs_lsn_t		tail_lsn;
>   
>   	/*
>   	 * We only want to pull the item from the AIL if its
> @@ -1034,10 +1035,11 @@ xfs_qm_dqflush_done(
>   	    ((lip->li_lsn == qip->qli_flush_lsn) ||
>   	     test_bit(XFS_LI_FAILED, &lip->li_flags))) {
>   
> -		/* xfs_trans_ail_delete() drops the AIL lock. */
>   		spin_lock(&ailp->ail_lock);
>   		if (lip->li_lsn == qip->qli_flush_lsn) {
> -			xfs_trans_ail_delete(ailp, lip, SHUTDOWN_CORRUPT_INCORE);
> +			/* xfs_ail_update_finish() drops the AIL lock */
> +			tail_lsn = xfs_ail_delete_one(ailp, lip);
> +			xfs_ail_update_finish(ailp, tail_lsn);
>   		} else {
>   			/*
>   			 * Clear the failed state since we are about to drop the
> diff --git a/fs/xfs/xfs_trans_ail.c b/fs/xfs/xfs_trans_ail.c
> index 2574d01e4a83..cfba691664c7 100644
> --- a/fs/xfs/xfs_trans_ail.c
> +++ b/fs/xfs/xfs_trans_ail.c
> @@ -864,13 +864,14 @@ xfs_ail_delete_one(
>    */
>   void
>   xfs_trans_ail_delete(
> -	struct xfs_ail		*ailp,
>   	struct xfs_log_item	*lip,
>   	int			shutdown_type)
>   {
> +	struct xfs_ail		*ailp = lip->li_ailp;
>   	struct xfs_mount	*mp = ailp->ail_mount;
>   	xfs_lsn_t		tail_lsn;
>   
> +	spin_lock(&ailp->ail_lock);
>   	if (!test_bit(XFS_LI_IN_AIL, &lip->li_flags)) {
>   		spin_unlock(&ailp->ail_lock);
>   		if (!XFS_FORCED_SHUTDOWN(mp)) {
> diff --git a/fs/xfs/xfs_trans_priv.h b/fs/xfs/xfs_trans_priv.h
> index 35655eac01a6..e4362fb8d483 100644
> --- a/fs/xfs/xfs_trans_priv.h
> +++ b/fs/xfs/xfs_trans_priv.h
> @@ -94,8 +94,7 @@ xfs_trans_ail_update(
>   xfs_lsn_t xfs_ail_delete_one(struct xfs_ail *ailp, struct xfs_log_item *lip);
>   void xfs_ail_update_finish(struct xfs_ail *ailp, xfs_lsn_t old_lsn)
>   			__releases(ailp->ail_lock);
> -void xfs_trans_ail_delete(struct xfs_ail *ailp, struct xfs_log_item *lip,
> -		int shutdown_type);
> +void xfs_trans_ail_delete(struct xfs_log_item *lip, int shutdown_type);
>   
>   static inline void
>   xfs_trans_ail_remove(
> @@ -103,13 +102,16 @@ xfs_trans_ail_remove(
>   	int			shutdown_type)
>   {
>   	struct xfs_ail		*ailp = lip->li_ailp;
> +	xfs_lsn_t		tail_lsn;
>   
>   	spin_lock(&ailp->ail_lock);
> -	/* xfs_trans_ail_delete() drops the AIL lock */
> -	if (test_bit(XFS_LI_IN_AIL, &lip->li_flags))
> -		xfs_trans_ail_delete(ailp, lip, shutdown_type);
> -	else
> +	/* xfs_ail_update_finish() drops the AIL lock */
> +	if (test_bit(XFS_LI_IN_AIL, &lip->li_flags)) {
> +		tail_lsn = xfs_ail_delete_one(ailp, lip);
> +		xfs_ail_update_finish(ailp, tail_lsn);
> +	} else {
>   		spin_unlock(&ailp->ail_lock);
> +	}
>   }
>   
>   void			xfs_ail_push(struct xfs_ail *, xfs_lsn_t);