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, 51 insertions, 0 deletions

diff --git a/fs/jffs2/writev.c b/fs/jffs2/writev.c
new file mode 100644
index 000000000..a1bda9dab
--- /dev/null
+++ b/fs/jffs2/writev.c
@@ -0,0 +1,51 @@
+/*
+ * JFFS2 -- Journalling Flash File System, Version 2.
+ *
+ * Copyright © 2001-2007 Red Hat, Inc.
+ *
+ * Created by David Woodhouse <dwmw2@infradead.org>
+ *
+ * For licensing information, see the file 'LICENCE' in this directory.
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/mtd/mtd.h>
+#include "nodelist.h"
+
+int jffs2_flash_direct_writev(struct jffs2_sb_info *c, const struct kvec *vecs,
+			      unsigned long count, loff_t to, size_t *retlen)
+{
+	if (!jffs2_is_writebuffered(c)) {
+		if (jffs2_sum_active()) {
+			int res;
+			res = jffs2_sum_add_kvec(c, vecs, count, (uint32_t) to);
+			if (res) {
+				return res;
+			}
+		}
+	}
+
+	return mtd_writev(c->mtd, vecs, count, to, retlen);
+}
+
+int jffs2_flash_direct_write(struct jffs2_sb_info *c, loff_t ofs, size_t len,
+			size_t *retlen, const u_char *buf)
+{
+	int ret;
+	ret = mtd_write(c->mtd, ofs, len, retlen, buf);
+
+	if (jffs2_sum_active()) {
+		struct kvec vecs[1];
+		int res;
+
+		vecs[0].iov_base = (unsigned char *) buf;
+		vecs[0].iov_len = len;
+
+		res = jffs2_sum_add_kvec(c, vecs, 1, (uint32_t) ofs);
+		if (res) {
+			return res;
+		}
+	}
+	return ret;
+}