KVM: Don't pre-reserve xarray entries when storing empty/NULL attributesgrafted

Skip the xarray reservation loop when clearing all memory attributes, as
storing NULL only erases the entry and never needs to allocate, so no
reservation (and no cleanup of a failed one) is required in that case.

Suggested-by: Sean Christopherson <seanjc@google.com>
Cc: David Ballesteros <davimaba.v@proton.me>
Signed-off-by: Zeng Chi <zengchi@kylinos.cn>
Link: https://patch.msgid.link/20260921102442.1232375-1-zeng_chi911@163.com
[sean: split to separate patch]
Signed-off-by: Sean Christopherson <seanjc@google.com>

1 files changed, 84 insertions, 0 deletions

diff --git a/drivers/md/dm-audit.c b/drivers/md/dm-audit.c
new file mode 100644
index 000000000..2e979eeb1
--- /dev/null
+++ b/drivers/md/dm-audit.c
@@ -0,0 +1,84 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Creating audit records for mapped devices.
+ *
+ * Copyright (C) 2021 Fraunhofer AISEC. All rights reserved.
+ *
+ * Authors: Michael Weiß <michael.weiss@aisec.fraunhofer.de>
+ */
+
+#include <linux/audit.h>
+#include <linux/module.h>
+#include <linux/device-mapper.h>
+#include <linux/bio.h>
+#include <linux/blkdev.h>
+
+#include "dm-audit.h"
+#include "dm-core.h"
+
+static struct audit_buffer *dm_audit_log_start(int audit_type,
+					       const char *dm_msg_prefix,
+					       const char *op)
+{
+	struct audit_buffer *ab;
+
+	if (audit_enabled == AUDIT_OFF)
+		return NULL;
+
+	ab = audit_log_start(audit_context(), GFP_KERNEL, audit_type);
+	if (unlikely(!ab))
+		return NULL;
+
+	audit_log_format(ab, "module=%s op=%s", dm_msg_prefix, op);
+	return ab;
+}
+
+void dm_audit_log_ti(int audit_type, const char *dm_msg_prefix, const char *op,
+		     struct dm_target *ti, int result)
+{
+	struct audit_buffer *ab = NULL;
+	struct mapped_device *md = dm_table_get_md(ti->table);
+	int dev_major = dm_disk(md)->major;
+	int dev_minor = dm_disk(md)->first_minor;
+
+	switch (audit_type) {
+	case AUDIT_DM_CTRL:
+		ab = dm_audit_log_start(audit_type, dm_msg_prefix, op);
+		if (unlikely(!ab))
+			return;
+		audit_log_task_info(ab);
+		audit_log_format(ab, " dev=%d:%d error_msg='%s'", dev_major,
+				 dev_minor, !result ? ti->error : "success");
+		break;
+	case AUDIT_DM_EVENT:
+		ab = dm_audit_log_start(audit_type, dm_msg_prefix, op);
+		if (unlikely(!ab))
+			return;
+		audit_log_format(ab, " dev=%d:%d sector=?", dev_major,
+				 dev_minor);
+		break;
+	default: /* unintended use */
+		return;
+	}
+
+	audit_log_format(ab, " res=%d", result);
+	audit_log_end(ab);
+}
+EXPORT_SYMBOL_GPL(dm_audit_log_ti);
+
+void dm_audit_log_bio(const char *dm_msg_prefix, const char *op,
+		      struct bio *bio, sector_t sector, int result)
+{
+	struct audit_buffer *ab;
+	int dev_major = MAJOR(bio->bi_bdev->bd_dev);
+	int dev_minor = MINOR(bio->bi_bdev->bd_dev);
+
+	ab = dm_audit_log_start(AUDIT_DM_EVENT, dm_msg_prefix, op);
+	if (unlikely(!ab))
+		return;
+
+	audit_log_format(ab, " dev=%d:%d sector=%llu res=%d",
+			 dev_major, dev_minor, sector, result);
+	audit_log_end(ab);
+}
+EXPORT_SYMBOL_GPL(dm_audit_log_bio);