On Thu, Nov 30, 2017 at 09:58:05AM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
>
> In certain cases we need to be able to maintain a buffer lock across a
> defer_finish call. Since there could be many (large) transactions
> committed as a result of a defer_finish, we have to hold the buffer
> across the roll, then immediately rejoin the buffer and mark it dirty in
> each transaction to keep the log moving forward.
>
> Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> ---
Seems about right to me. A couple things..
> fs/xfs/libxfs/xfs_defer.c | 37 ++++++++++++++++++++++++++++++++++---
> fs/xfs/libxfs/xfs_defer.h | 5 ++++-
> 2 files changed, 38 insertions(+), 4 deletions(-)
>
> diff --git a/fs/xfs/libxfs/xfs_defer.c b/fs/xfs/libxfs/xfs_defer.c
> index 072ebfe..b5b3414 100644
> --- a/fs/xfs/libxfs/xfs_defer.c
> +++ b/fs/xfs/libxfs/xfs_defer.c
> @@ -249,6 +249,10 @@ xfs_defer_trans_roll(
> for (i = 0; i < XFS_DEFER_OPS_NR_INODES && dop->dop_inodes[i]; i++)
> xfs_trans_log_inode(*tp, dop->dop_inodes[i], XFS_ILOG_CORE);
>
> + /* Hold the (previously bjoin'd) buffer locked across the roll. */
> + for (i = 0; i < XFS_DEFER_OPS_NR_BUFS && dop->dop_bufs[i]; i++)
> + xfs_trans_bhold(*tp, dop->dop_bufs[i]);
> +
It seems more consistent to dirty the buffer in the tx here and
bjoin+bhold it in the loop below.
> trace_xfs_defer_trans_roll((*tp)->t_mountp, dop);
>
> /* Roll the transaction. */
> @@ -264,6 +268,12 @@ xfs_defer_trans_roll(
> for (i = 0; i < XFS_DEFER_OPS_NR_INODES && dop->dop_inodes[i]; i++)
> xfs_trans_ijoin(*tp, dop->dop_inodes[i], 0);
>
> + /* Rejoin the buffers and dirty them so the log moves forward. */
> + for (i = 0; i < XFS_DEFER_OPS_NR_BUFS && dop->dop_bufs[i]; i++) {
> + xfs_trans_bjoin(*tp, dop->dop_bufs[i]);
> + xfs_trans_dirty_buf(*tp, dop->dop_bufs[i]);
> + }
> +
> return error;
> }
>
> @@ -299,6 +309,29 @@ xfs_defer_ijoin(
> }
>
> /*
> + * Add this buffer to the deferred op. Each joined buffer is relogged
> + * each time we roll the transaction.
> + */
> +int
> +xfs_defer_bjoin(
> + struct xfs_defer_ops *dop,
> + struct xfs_buf *bp)
> +{
> + int i;
> +
> + for (i = 0; i < XFS_DEFER_OPS_NR_BUFS; i++) {
> + if (dop->dop_bufs[i] == bp)
> + return 0;
> + else if (dop->dop_bufs[i] == NULL) {
> + dop->dop_bufs[i] = bp;
> + return 0;
> + }
> + }
> +
> + return -EFSCORRUPTED;
I notice that this looks exactly like xfs_defer_join(), but is
-EFSCORRUPTED the right error here? It probably doesn't matter that much
given that if we hit this we've already lost, but I wonder if an error
that more reflects a programming error as opposed to inconsistent fs
might be more appropriate..? -EINVAL, -EBUSY?
Brian
> +}
> +
> +/*
> * Finish all the pending work. This involves logging intent items for
> * any work items that wandered in since the last transaction roll (if
> * one has even happened), rolling the transaction, and finishing the
> @@ -493,9 +526,7 @@ xfs_defer_init(
> struct xfs_defer_ops *dop,
> xfs_fsblock_t *fbp)
> {
> - dop->dop_committed = false;
> - dop->dop_low = false;
> - memset(&dop->dop_inodes, 0, sizeof(dop->dop_inodes));
> + memset(dop, 0, sizeof(struct xfs_defer_ops));
> *fbp = NULLFSBLOCK;
> INIT_LIST_HEAD(&dop->dop_intake);
> INIT_LIST_HEAD(&dop->dop_pending);
> diff --git a/fs/xfs/libxfs/xfs_defer.h b/fs/xfs/libxfs/xfs_defer.h
> index d4f046d..045beac 100644
> --- a/fs/xfs/libxfs/xfs_defer.h
> +++ b/fs/xfs/libxfs/xfs_defer.h
> @@ -59,6 +59,7 @@ enum xfs_defer_ops_type {
> };
>
> #define XFS_DEFER_OPS_NR_INODES 2 /* join up to two inodes */
> +#define XFS_DEFER_OPS_NR_BUFS 2 /* join up to two buffers */
>
> struct xfs_defer_ops {
> bool dop_committed; /* did any trans commit? */
> @@ -66,8 +67,9 @@ struct xfs_defer_ops {
> struct list_head dop_intake; /* unlogged pending work */
> struct list_head dop_pending; /* logged pending work */
>
> - /* relog these inodes with each roll */
> + /* relog these with each roll */
> struct xfs_inode *dop_inodes[XFS_DEFER_OPS_NR_INODES];
> + struct xfs_buf *dop_bufs[XFS_DEFER_OPS_NR_BUFS];
> };
>
> void xfs_defer_add(struct xfs_defer_ops *dop, enum xfs_defer_ops_type type,
> @@ -77,6 +79,7 @@ void xfs_defer_cancel(struct xfs_defer_ops *dop);
> void xfs_defer_init(struct xfs_defer_ops *dop, xfs_fsblock_t *fbp);
> bool xfs_defer_has_unfinished_work(struct xfs_defer_ops *dop);
> int xfs_defer_ijoin(struct xfs_defer_ops *dop, struct xfs_inode *ip);
> +int xfs_defer_bjoin(struct xfs_defer_ops *dop, struct xfs_buf *bp);
>
> /* Description of a deferred type. */
> struct xfs_defer_op_type {
> --
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