xfs: automatic dfops buffer relogging

Buffers that are held across deferred operations are explicitly
joined to the dfops structure to ensure appropriate relogging.
While buffers are currently joined explicitly, we can detect the
conditions that require relogging at dfops finish time by inspecting
the transaction item list for held buffers.

Replace the xfs_defer_bjoin() infrastructure with such detection and
automatic relogging of held buffers. This eliminates the need for
the per-dfops buffer list, replaced by an on-stack variant in
xfs_defer_trans_roll().

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

1 files changed, 26 insertions, 32 deletions

diff --git a/fs/xfs/libxfs/xfs_defer.c b/fs/xfs/libxfs/xfs_defer.c
index 64e1abc60edc..e9b7671d289a 100644
--- a/fs/xfs/libxfs/xfs_defer.c
+++ b/fs/xfs/libxfs/xfs_defer.c
@@ -14,6 +14,7 @@
 #include "xfs_mount.h"
 #include "xfs_defer.h"
 #include "xfs_trans.h"
+#include "xfs_buf_item.h"
 #include "xfs_trace.h"
 
 /*
@@ -228,6 +229,10 @@ xfs_defer_trans_roll(
 	struct xfs_trans		**tp)
 {
 	struct xfs_defer_ops		*dop = (*tp)->t_dfops;
+	struct xfs_buf_log_item		*bli;
+	struct xfs_log_item		*lip;
+	struct xfs_buf			*bplist[XFS_DEFER_OPS_NR_BUFS];
+	int				bpcount = 0;
 	int				i;
 	int				error;
 
@@ -235,9 +240,24 @@ 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]);
+	list_for_each_entry(lip, &(*tp)->t_items, li_trans) {
+		switch (lip->li_type) {
+		case XFS_LI_BUF:
+			bli = container_of(lip, struct xfs_buf_log_item,
+					   bli_item);
+			if (bli->bli_flags & XFS_BLI_HOLD) {
+				if (bpcount >= XFS_DEFER_OPS_NR_BUFS) {
+					ASSERT(0);
+					return -EFSCORRUPTED;
+				}
+				xfs_trans_dirty_buf(*tp, bli->bli_buf);
+				bplist[bpcount++] = bli->bli_buf;
+			}
+			break;
+		default:
+			break;
+		}
+	}
 
 	trace_xfs_defer_trans_roll((*tp)->t_mountp, dop, _RET_IP_);
 
@@ -255,9 +275,9 @@ xfs_defer_trans_roll(
 		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]);
+	for (i = 0; i < bpcount; i++) {
+		xfs_trans_bjoin(*tp, bplist[i]);
+		xfs_trans_bhold(*tp, bplist[i]);
 	}
 
 	return error;
@@ -296,30 +316,6 @@ 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;
-		}
-	}
-
-	ASSERT(0);
-	return -EFSCORRUPTED;
-}
-
-/*
  * Reset an already used dfops after finish.
  */
 static void
@@ -331,7 +327,6 @@ xfs_defer_reset(
 	ASSERT(!xfs_defer_has_unfinished_work(dop));
 
 	memset(dop->dop_inodes, 0, sizeof(dop->dop_inodes));
-	memset(dop->dop_bufs, 0, sizeof(dop->dop_bufs));
 
 	/*
 	 * Low mode state transfers across transaction rolls to mirror dfops
@@ -594,7 +589,6 @@ xfs_defer_move(
 	list_splice_init(&src->dop_pending, &dst->dop_pending);
 
 	memcpy(dst->dop_inodes, src->dop_inodes, sizeof(dst->dop_inodes));
-	memcpy(dst->dop_bufs, src->dop_bufs, sizeof(dst->dop_bufs));
 
 	/*
 	 * Low free space mode was historically controlled by a dfops field.