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, 132 insertions, 0 deletions

diff --git a/include/trace/events/readahead.h b/include/trace/events/readahead.h
new file mode 100644
index 000000000..087f171e2
--- /dev/null
+++ b/include/trace/events/readahead.h
@@ -0,0 +1,132 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM readahead
+
+#if !defined(_TRACE_FILEMAP_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_READAHEAD_H
+
+#include <linux/types.h>
+#include <linux/tracepoint.h>
+#include <linux/mm.h>
+#include <linux/fs.h>
+#include <linux/pagemap.h>
+
+TRACE_EVENT(page_cache_ra_unbounded,
+	TP_PROTO(struct inode *inode, pgoff_t index, unsigned long nr_to_read,
+		 unsigned long lookahead_size),
+
+	TP_ARGS(inode, index, nr_to_read, lookahead_size),
+
+	TP_STRUCT__entry(
+		__field(u64, i_ino)
+		__field(dev_t, s_dev)
+		__field(pgoff_t, index)
+		__field(unsigned long, nr_to_read)
+		__field(unsigned long, lookahead_size)
+	),
+
+	TP_fast_assign(
+		__entry->i_ino = inode->i_ino;
+		__entry->s_dev = inode->i_sb->s_dev;
+		__entry->index = index;
+		__entry->nr_to_read = nr_to_read;
+		__entry->lookahead_size = lookahead_size;
+	),
+
+	TP_printk(
+		"dev=%d:%d ino=%llx index=%lu nr_to_read=%lu lookahead_size=%lu",
+		MAJOR(__entry->s_dev), MINOR(__entry->s_dev), __entry->i_ino,
+		__entry->index, __entry->nr_to_read, __entry->lookahead_size
+	)
+);
+
+TRACE_EVENT(page_cache_ra_order,
+	TP_PROTO(struct inode *inode, pgoff_t index, struct file_ra_state *ra),
+
+	TP_ARGS(inode, index, ra),
+
+	TP_STRUCT__entry(
+		__field(u64, i_ino)
+		__field(dev_t, s_dev)
+		__field(pgoff_t, index)
+		__field(unsigned int, order)
+		__field(unsigned int, size)
+		__field(unsigned int, async_size)
+		__field(unsigned int, ra_pages)
+	),
+
+	TP_fast_assign(
+		__entry->i_ino = inode->i_ino;
+		__entry->s_dev = inode->i_sb->s_dev;
+		__entry->index = index;
+		__entry->order = ra->order;
+		__entry->size = ra->size;
+		__entry->async_size = ra->async_size;
+		__entry->ra_pages = ra->ra_pages;
+	),
+
+	TP_printk(
+		"dev=%d:%d ino=%llx index=%lu order=%u size=%u async_size=%u ra_pages=%u",
+		MAJOR(__entry->s_dev), MINOR(__entry->s_dev), __entry->i_ino,
+		__entry->index, __entry->order, __entry->size,
+		__entry->async_size, __entry->ra_pages
+	)
+);
+
+DECLARE_EVENT_CLASS(page_cache_ra_op,
+	TP_PROTO(struct inode *inode, pgoff_t index, struct file_ra_state *ra,
+		 unsigned long req_count),
+
+	TP_ARGS(inode, index, ra, req_count),
+
+	TP_STRUCT__entry(
+		__field(u64, i_ino)
+		__field(loff_t, prev_pos)
+		__field(pgoff_t, index)
+		__field(unsigned long, req_count)
+		__field(dev_t, s_dev)
+		__field(unsigned int, order)
+		__field(unsigned int, size)
+		__field(unsigned int, async_size)
+		__field(unsigned int, ra_pages)
+		__field(unsigned int, mmap_miss)
+	),
+
+	TP_fast_assign(
+		__entry->i_ino = inode->i_ino;
+		__entry->s_dev = inode->i_sb->s_dev;
+		__entry->index = index;
+		__entry->order = ra->order;
+		__entry->size = ra->size;
+		__entry->async_size = ra->async_size;
+		__entry->ra_pages = ra->ra_pages;
+		__entry->mmap_miss = ra->mmap_miss;
+		__entry->prev_pos = ra->prev_pos;
+		__entry->req_count = req_count;
+	),
+
+	TP_printk(
+		"dev=%d:%d ino=%llx index=%lu req_count=%lu order=%u size=%u async_size=%u ra_pages=%u mmap_miss=%u prev_pos=%lld",
+		MAJOR(__entry->s_dev), MINOR(__entry->s_dev), __entry->i_ino,
+		__entry->index, __entry->req_count, __entry->order,
+		__entry->size, __entry->async_size, __entry->ra_pages,
+		__entry->mmap_miss, __entry->prev_pos
+	)
+);
+
+DEFINE_EVENT(page_cache_ra_op, page_cache_sync_ra,
+	TP_PROTO(struct inode *inode, pgoff_t index, struct file_ra_state *ra,
+		 unsigned long req_count),
+	TP_ARGS(inode, index, ra, req_count)
+);
+
+DEFINE_EVENT(page_cache_ra_op, page_cache_async_ra,
+	TP_PROTO(struct inode *inode, pgoff_t index, struct file_ra_state *ra,
+		 unsigned long req_count),
+	TP_ARGS(inode, index, ra, req_count)
+);
+
+#endif /* _TRACE_FILEMAP_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>