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, 269 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-fs-nilfs2 b/Documentation/ABI/testing/sysfs-fs-nilfs2
new file mode 100644
index 000000000..304ba84a9
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-fs-nilfs2
@@ -0,0 +1,269 @@
+
+What:		/sys/fs/nilfs2/features/revision
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show current revision of NILFS file system driver.
+		This value informs about file system revision that
+		driver is ready to support.
+
+What:		/sys/fs/nilfs2/features/README
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Describe attributes of /sys/fs/nilfs2/features group.
+
+What:		/sys/fs/nilfs2/<device>/revision
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show NILFS file system revision on volume.
+		This value informs about metadata structures'
+		revision on mounted volume.
+
+What:		/sys/fs/nilfs2/<device>/blocksize
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show volume's block size in bytes.
+
+What:		/sys/fs/nilfs2/<device>/device_size
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show volume size in bytes.
+
+What:		/sys/fs/nilfs2/<device>/free_blocks
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show count of free blocks on volume.
+
+What:		/sys/fs/nilfs2/<device>/uuid
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show volume's UUID (Universally Unique Identifier).
+
+What:		/sys/fs/nilfs2/<device>/volume_name
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show volume's label.
+
+What:		/sys/fs/nilfs2/<device>/README
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Describe attributes of /sys/fs/nilfs2/<device> group.
+
+What:		/sys/fs/nilfs2/<device>/superblock/sb_write_time
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show last write time of super block in human-readable
+		format.
+
+What:		/sys/fs/nilfs2/<device>/superblock/sb_write_time_secs
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show last write time of super block in seconds.
+
+What:		/sys/fs/nilfs2/<device>/superblock/sb_write_count
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show current write count of super block.
+
+What:		/sys/fs/nilfs2/<device>/superblock/sb_update_frequency
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show/Set interval of periodical update of superblock
+		(in seconds).
+
+What:		/sys/fs/nilfs2/<device>/superblock/README
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Describe attributes of /sys/fs/nilfs2/<device>/superblock
+		group.
+
+What:		/sys/fs/nilfs2/<device>/segctor/last_pseg_block
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show start block number of the latest segment.
+
+What:		/sys/fs/nilfs2/<device>/segctor/last_seg_sequence
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show sequence value of the latest segment.
+
+What:		/sys/fs/nilfs2/<device>/segctor/last_seg_checkpoint
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show checkpoint number of the latest segment.
+
+What:		/sys/fs/nilfs2/<device>/segctor/current_seg_sequence
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show segment sequence counter.
+
+What:		/sys/fs/nilfs2/<device>/segctor/current_last_full_seg
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show index number of the latest full segment.
+
+What:		/sys/fs/nilfs2/<device>/segctor/next_full_seg
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show index number of the full segment index
+		to be used next.
+
+What:		/sys/fs/nilfs2/<device>/segctor/next_pseg_offset
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show offset of next partial segment in the current
+		full segment.
+
+What:		/sys/fs/nilfs2/<device>/segctor/next_checkpoint
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show next checkpoint number.
+
+What:		/sys/fs/nilfs2/<device>/segctor/last_seg_write_time
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show write time of the last segment in
+		human-readable format.
+
+What:		/sys/fs/nilfs2/<device>/segctor/last_seg_write_time_secs
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show write time of the last segment in seconds.
+
+What:		/sys/fs/nilfs2/<device>/segctor/last_nongc_write_time
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show write time of the last segment not for cleaner
+		operation in human-readable format.
+
+What:		/sys/fs/nilfs2/<device>/segctor/last_nongc_write_time_secs
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show write time of the last segment not for cleaner
+		operation in seconds.
+
+What:		/sys/fs/nilfs2/<device>/segctor/dirty_data_blocks_count
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show number of dirty data blocks.
+
+What:		/sys/fs/nilfs2/<device>/segctor/README
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Describe attributes of /sys/fs/nilfs2/<device>/segctor
+		group.
+
+What:		/sys/fs/nilfs2/<device>/segments/segments_number
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show number of segments on a volume.
+
+What:		/sys/fs/nilfs2/<device>/segments/blocks_per_segment
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show number of blocks in segment.
+
+What:		/sys/fs/nilfs2/<device>/segments/clean_segments
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show count of clean segments.
+
+What:		/sys/fs/nilfs2/<device>/segments/dirty_segments
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show count of dirty segments.
+
+What:		/sys/fs/nilfs2/<device>/segments/README
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Describe attributes of /sys/fs/nilfs2/<device>/segments
+		group.
+
+What:		/sys/fs/nilfs2/<device>/checkpoints/checkpoints_number
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show number of checkpoints on volume.
+
+What:		/sys/fs/nilfs2/<device>/checkpoints/snapshots_number
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show number of snapshots on volume.
+
+What:		/sys/fs/nilfs2/<device>/checkpoints/last_seg_checkpoint
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show checkpoint number of the latest segment.
+
+What:		/sys/fs/nilfs2/<device>/checkpoints/next_checkpoint
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show next checkpoint number.
+
+What:		/sys/fs/nilfs2/<device>/checkpoints/README
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Describe attributes of /sys/fs/nilfs2/<device>/checkpoints
+		group.
+
+What:		/sys/fs/nilfs2/<device>/mounted_snapshots/README
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Describe content of /sys/fs/nilfs2/<device>/mounted_snapshots
+		group.
+
+What:		/sys/fs/nilfs2/<device>/mounted_snapshots/<id>/inodes_count
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show number of inodes for snapshot.
+
+What:		/sys/fs/nilfs2/<device>/mounted_snapshots/<id>/blocks_count
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show number of blocks for snapshot.
+
+What:		/sys/fs/nilfs2/<device>/mounted_snapshots/<id>/README
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Describe attributes of /sys/fs/nilfs2/<device>/mounted_snapshots/<id>
+		group.