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Subject[PATCH 4.14 68/70] xfs: add the ability to join a held buffer to a defer_ops
Date
From: Darrick J. Wong <darrick.wong@oracle.com>

commit b7b2846fe26f2c0d7f317c874a13d3ecf22670ff upstream.

In certain cases, defer_ops callers will lock a buffer and want to hold
the lock across transaction rolls. Similar to ijoined inodes, we want
to dirty & join the buffer with each transaction roll in defer_finish so
that afterwards the caller still owns the buffer lock and we haven't
inadvertently pinned the log.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Lyakas <alex@zadara.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/xfs/libxfs/xfs_defer.c | 39 ++++++++++++++++++++++++++++++++++++---
fs/xfs/libxfs/xfs_defer.h | 5 ++++-
2 files changed, 40 insertions(+), 4 deletions(-)

--- 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_dirty_buf(*tp, dop->dop_bufs[i]);
+
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_bhold(*tp, dop->dop_bufs[i]);
+ }
+
return error;
}

@@ -295,6 +305,31 @@ xfs_defer_ijoin(
}
}

+ ASSERT(0);
+ return -EFSCORRUPTED;
+}
+
+/*
+ * 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;
+ }
+ }
+
+ ASSERT(0);
return -EFSCORRUPTED;
}

@@ -493,9 +528,7 @@ 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);
--- 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_o
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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