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, 66 insertions, 0 deletions

diff --git a/Documentation/admin-guide/jfs.rst b/Documentation/admin-guide/jfs.rst
new file mode 100644
index 000000000..9e12d936b
--- /dev/null
+++ b/Documentation/admin-guide/jfs.rst
@@ -0,0 +1,66 @@
+===========================================
+IBM's Journaled File System (JFS) for Linux
+===========================================
+
+JFS Homepage:  http://jfs.sourceforge.net/
+
+The following mount options are supported:
+
+(*) == default
+
+iocharset=name
+                Character set to use for converting from Unicode to
+		ASCII.  The default is to do no conversion.  Use
+		iocharset=utf8 for UTF-8 translations.  This requires
+		CONFIG_NLS_UTF8 to be set in the kernel .config file.
+		iocharset=none specifies the default behavior explicitly.
+
+resize=value
+                Resize the volume to <value> blocks.  JFS only supports
+		growing a volume, not shrinking it.  This option is only
+		valid during a remount, when the volume is mounted
+		read-write.  The resize keyword with no value will grow
+		the volume to the full size of the partition.
+
+nointegrity
+                Do not write to the journal.  The primary use of this option
+		is to allow for higher performance when restoring a volume
+		from backup media.  The integrity of the volume is not
+		guaranteed if the system abnormally abends.
+
+integrity(*)
+                Commit metadata changes to the journal.  Use this option to
+		remount a volume where the nointegrity option was
+		previously specified in order to restore normal behavior.
+
+errors=continue
+                        Keep going on a filesystem error.
+errors=remount-ro(*)
+                        Remount the filesystem read-only on an error.
+errors=panic
+                        Panic and halt the machine if an error occurs.
+
+uid=value
+                Override on-disk uid with specified value
+gid=value
+                Override on-disk gid with specified value
+umask=value
+                Override on-disk umask with specified octal value. For
+                directories, the execute bit will be set if the corresponding
+		read bit is set.
+
+discard=minlen, discard/nodiscard(*)
+                This enables/disables the use of discard/TRIM commands.
+		The discard/TRIM commands are sent to the underlying
+                block device when blocks are freed. This is useful for SSD
+                devices and sparse/thinly-provisioned LUNs.  The FITRIM ioctl
+		command is also available together with the nodiscard option.
+		The value of minlen specifies the minimum blockcount, when
+		a TRIM command to the block device is considered useful.
+		When no value is given to the discard option, it defaults to
+		64 blocks, which means 256KiB in JFS.
+		The minlen value of discard overrides the minlen value given
+		on an FITRIM ioctl().
+
+The JFS mailing list can be subscribed to by using the link labeled
+"Mail list Subscribe" at our web page http://jfs.sourceforge.net/