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, 33 insertions, 0 deletions

diff --git a/drivers/md/raid0.h b/drivers/md/raid0.h
new file mode 100644
index 000000000..8cc761ca7
--- /dev/null
+++ b/drivers/md/raid0.h
@@ -0,0 +1,33 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _RAID0_H
+#define _RAID0_H
+
+struct strip_zone {
+	sector_t zone_end;	/* Start of the next zone (in sectors) */
+	sector_t dev_start;	/* Zone offset in real dev (in sectors) */
+	int	 nb_dev;	/* # of devices attached to the zone */
+	int	 disk_shift;	/* start disk for the original layout */
+};
+
+/* Linux 3.14 (20d0189b101) made an unintended change to
+ * the RAID0 layout for multi-zone arrays (where devices aren't all
+ * the same size.
+ * RAID0_ORIG_LAYOUT restores the original layout
+ * RAID0_ALT_MULTIZONE_LAYOUT uses the altered layout
+ * The layouts are identical when there is only one zone (all
+ * devices the same size).
+ */
+
+enum r0layout {
+	RAID0_ORIG_LAYOUT = 1,
+	RAID0_ALT_MULTIZONE_LAYOUT = 2,
+};
+struct r0conf {
+	struct strip_zone	*strip_zone;
+	struct md_rdev		**devlist; /* lists of rdevs, pointed to
+					    * by strip_zone->dev */
+	int			nr_strip_zones;
+	enum r0layout		layout;
+};
+
+#endif