Re: [PATCH 10/24] xfs: clean up the buffer iodone callback functions

Darrick J. Wong
2020-05-22T22:28:19Z

On Fri, May 22, 2020 at 01:50:15PM +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
>
> Now that we've sorted inode and dquot buffers, we can apply the same
> cleanups to dirty buffers with buffer log items. They only have one
> callback, too, so we don't need the log item callback. Collapse the
> iodone functions and remove all the now unnecessary infrastructure
> around callback processing.
>
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> ---
> fs/xfs/xfs_buf_item.c | 139 +++++++++--------------------------------
> fs/xfs/xfs_buf_item.h | 1 -
> fs/xfs/xfs_trans_buf.c | 2 -
> 3 files changed, 29 insertions(+), 113 deletions(-)
>
> diff --git a/fs/xfs/xfs_buf_item.c b/fs/xfs/xfs_buf_item.c
> index 57e5d37f6852e..d44b3e3f46613 100644
> --- a/fs/xfs/xfs_buf_item.c
> +++ b/fs/xfs/xfs_buf_item.c
> @@ -30,7 +30,7 @@ static inline struct xfs_buf_log_item *BUF_ITEM(struct xfs_log_item *lip)
> return container_of(lip, struct xfs_buf_log_item, bli_item);
> }
>
> -STATIC void xfs_buf_do_callbacks(struct xfs_buf *bp);
> +static void xfs_buf_item_done(struct xfs_buf *bp);
>
> /* Is this log iovec plausibly large enough to contain the buffer log format? */
> bool
> @@ -462,9 +462,8 @@ xfs_buf_item_unpin(
> * the AIL lock.
> */
> if (bip->bli_flags & XFS_BLI_STALE_INODE) {
> - lip->li_cb(bp, lip);
> + xfs_buf_item_done(bp);
> xfs_iflush_done(bp);
> - bp->b_log_item = NULL;
> } else {
> xfs_trans_ail_delete(lip, SHUTDOWN_LOG_IO_ERROR);
> xfs_buf_item_relse(bp);
> @@ -973,46 +972,6 @@ xfs_buf_attach_iodone(
> list_add_tail(&lip->li_bio_list, &bp->b_li_list);
> }
>
> -/*
> - * We can have many callbacks on a buffer. Running the callbacks individually
> - * can cause a lot of contention on the AIL lock, so we allow for a single
> - * callback to be able to scan the remaining items in bp->b_li_list for other
> - * items of the same type and callback to be processed in the first call.
> - *
> - * As a result, the loop walking the callback list below will also modify the
> - * list. it removes the first item from the list and then runs the callback.
> - * The loop then restarts from the new first item int the list. This allows the
> - * callback to scan and modify the list attached to the buffer and we don't
> - * have to care about maintaining a next item pointer.
> - */
> -STATIC void
> -xfs_buf_do_callbacks(
> - struct xfs_buf *bp)
> -{
> - struct xfs_buf_log_item *blip = bp->b_log_item;
> - struct xfs_log_item *lip;
> -
> - /* If there is a buf_log_item attached, run its callback */
> - if (blip) {
> - lip = &blip->bli_item;
> - lip->li_cb(bp, lip);
> - }
> -
> - while (!list_empty(&bp->b_li_list)) {
> - lip = list_first_entry(&bp->b_li_list, struct xfs_log_item,
> - li_bio_list);
> -
> - /*
> - * Remove the item from the list, so we don't have any
> - * confusion if the item is added to another buf.
> - * Don't touch the log item after calling its
> - * callback, because it could have freed itself.
> - */
> - list_del_init(&lip->li_bio_list);
> - lip->li_cb(bp, lip);
> - }
> -}
> -
> /*
> * Invoke the error state callback for each log item affected by the failed I/O.
> *
> @@ -1025,8 +984,8 @@ STATIC void
> xfs_buf_do_callbacks_fail(
> struct xfs_buf *bp)
> {
> + struct xfs_ail *ailp = bp->b_mount->m_ail;
> struct xfs_log_item *lip;
> - struct xfs_ail *ailp;
>
> /*
> * Buffer log item errors are handled directly by xfs_buf_item_push()
> @@ -1036,9 +995,6 @@ xfs_buf_do_callbacks_fail(
> if (list_empty(&bp->b_li_list))
> return;
>
> - lip = list_first_entry(&bp->b_li_list, struct xfs_log_item,
> - li_bio_list);
> - ailp = lip->li_ailp;
> spin_lock(&ailp->ail_lock);
> list_for_each_entry(lip, &bp->b_li_list, li_bio_list) {
> if (lip->li_ops->iop_error)
> @@ -1051,22 +1007,11 @@ static bool
> xfs_buf_iodone_callback_error(
> struct xfs_buf *bp)
> {
> - struct xfs_buf_log_item *bip = bp->b_log_item;
> - struct xfs_log_item *lip;
> - struct xfs_mount *mp;
> + struct xfs_mount *mp = bp->b_mount;
> static ulong lasttime;
> static xfs_buftarg_t *lasttarg;
> struct xfs_error_cfg *cfg;
>
> - /*
> - * The failed buffer might not have a buf_log_item attached or the
> - * log_item list might be empty. Get the mp from the available
> - * xfs_log_item
> - */
> - lip = list_first_entry_or_null(&bp->b_li_list, struct xfs_log_item,
> - li_bio_list);
> - mp = lip ? lip->li_mountp : bip->bli_item.li_mountp;
> -
> /*
> * If we've already decided to shutdown the filesystem because of
> * I/O errors, there's no point in giving this a retry.
> @@ -1171,14 +1116,27 @@ xfs_buf_had_callback_errors(
> }
>
> static void
> -xfs_buf_run_callbacks(
> +xfs_buf_item_done(
> struct xfs_buf *bp)
> {
> + struct xfs_buf_log_item *bip = bp->b_log_item;
>
> - if (xfs_buf_had_callback_errors(bp))
> + if (!bip)
> return;
> - xfs_buf_do_callbacks(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.
> + *
> + * Either way, AIL is useless if we're forcing a shutdown.
> + */
> + xfs_trans_ail_delete(&bip->bli_item, SHUTDOWN_CORRUPT_INCORE);
> bp->b_log_item = NULL;
> + xfs_buf_item_free(bip);
> + xfs_buf_rele(bp);
> }
>
> /*
> @@ -1188,19 +1146,10 @@ void
> xfs_buf_inode_iodone(
> struct xfs_buf *bp)
> {
> - struct xfs_buf_log_item *blip = bp->b_log_item;
> - struct xfs_log_item *lip;
> -
> if (xfs_buf_had_callback_errors(bp))
> return;
>
> - /* If there is a buf_log_item attached, run its callback */
> - if (blip) {
> - lip = &blip->bli_item;
> - lip->li_cb(bp, lip);
> - bp->b_log_item = NULL;
> - }
> -
> + xfs_buf_item_done(bp);
> xfs_iflush_done(bp);

Just out of curiosity, we still have a reference to bp here even if
xfs_buf_item_done calls xfs_buf_rele, right? I think the answer is that yes
we do still have the reference because the inodes themselves hold references
to the cluster buffer, right?

If so,
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

--D

> xfs_buf_ioend_finish(bp);
> }
> @@ -1212,59 +1161,29 @@ void
> xfs_buf_dquot_iodone(
> struct xfs_buf *bp)
> {
> - struct xfs_buf_log_item *blip = bp->b_log_item;
> - struct xfs_log_item *lip;
> -
> if (xfs_buf_had_callback_errors(bp))
> return;
>
> /* a newly allocated dquot buffer might have a log item attached */
> - if (blip) {
> - lip = &blip->bli_item;
> - lip->li_cb(bp, lip);
> - bp->b_log_item = NULL;
> - }
> -
> + xfs_buf_item_done(bp);
> xfs_dquot_done(bp);
> xfs_buf_ioend_finish(bp);
> }
>
> /*
> * Dirty buffer iodone callback function.
> + *
> + * Note that for things like remote attribute buffers, there may not be a buffer
> + * log item here, so processing the buffer log item must remain be optional.
> */
> void
> xfs_buf_dirty_iodone(
> struct xfs_buf *bp)
> {
> - xfs_buf_run_callbacks(bp);
> + if (xfs_buf_had_callback_errors(bp))
> + return;
> +
> + xfs_buf_item_done(bp);
> xfs_buf_ioend_finish(bp);
> }
>
> -/*
> - * This is the iodone() function for buffers which have been
> - * logged. It is called when they are eventually flushed out.
> - * It should remove the buf item from the AIL, and free the buf item.
> - * It is called by xfs_buf_iodone_callbacks() above which will take
> - * care of cleaning up the buffer itself.
> - */
> -void
> -xfs_buf_iodone(
> - struct xfs_buf *bp,
> - struct xfs_log_item *lip)
> -{
> - 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.
> - *
> - * Either way, AIL is useless if we're forcing a shutdown.
> - */
> - xfs_trans_ail_delete(lip, SHUTDOWN_CORRUPT_INCORE);
> - xfs_buf_item_free(BUF_ITEM(lip));
> -}
> diff --git a/fs/xfs/xfs_buf_item.h b/fs/xfs/xfs_buf_item.h
> index 96f994ec90915..3f436efb0b67a 100644
> --- a/fs/xfs/xfs_buf_item.h
> +++ b/fs/xfs/xfs_buf_item.h
> @@ -57,7 +57,6 @@ bool xfs_buf_item_dirty_format(struct xfs_buf_log_item *);
> void xfs_buf_attach_iodone(struct xfs_buf *,
> void(*)(struct xfs_buf *, struct xfs_log_item *),
> struct xfs_log_item *);
> -void xfs_buf_iodone(struct xfs_buf *, struct xfs_log_item *);
> void xfs_buf_inode_iodone(struct xfs_buf *);
> void xfs_buf_dquot_iodone(struct xfs_buf *);
> void xfs_buf_dirty_iodone(struct xfs_buf *);
> diff --git a/fs/xfs/xfs_trans_buf.c b/fs/xfs/xfs_trans_buf.c
> index 69e0ebe94a915..11cd666cd99a6 100644
> --- a/fs/xfs/xfs_trans_buf.c
> +++ b/fs/xfs/xfs_trans_buf.c
> @@ -475,7 +475,6 @@ xfs_trans_dirty_buf(
> bp->b_flags |= XBF_DONE;
>
> ASSERT(atomic_read(&bip->bli_refcount) > 0);
> - bip->bli_item.li_cb = xfs_buf_iodone;
>
> /*
> * If we invalidated the buffer within this transaction, then
> @@ -644,7 +643,6 @@ xfs_trans_stale_inode_buf(
> ASSERT(atomic_read(&bip->bli_refcount) > 0);
>
> bip->bli_flags |= XFS_BLI_STALE_INODE;
> - bip->bli_item.li_cb = xfs_buf_iodone;
> bp->b_flags |= _XBF_INODES;
> xfs_trans_buf_set_type(tp, bp, XFS_BLFT_DINO_BUF);
> }
> --
> 2.26.2.761.g0e0b3e54be
>