Merge: Backport upstream commit "fs: Add 'initramfs_options' to set initramfs mount options

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/7528

JIRA: https://issues.redhat.com/browse/RHEL-121113

Upstream commit 278033a ("fs: Add 'initramfs_options' to set initramfs mount options") allows for passing of options to the initial root file system so that there is more control over allocation of memory for this memory based file system.

In the target case the memory requirement of kdump can be significantly reduced so that we will have less OOM issues with kdump.

Signed-off-by: Ian Kent <ikent@redhat.com>

Approved-by: Brian Foster <bfoster@redhat.com>
Approved-by: Miklos Szeredi <mszeredi@redhat.com>
Approved-by: Carlos Maiolino <cmaiolino@redhat.com>
Approved-by: Andrey Albershteyn <aalbersh@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>

Merged-by: CKI GitLab Kmaint Pipeline Bot <26919896-cki-kmaint-pipeline-bot@users.noreply.gitlab.com>

Author: CKI KWF Bot

Documentation/admin-guide/kernel-parameters.txt

@@ -5765,6 +5765,9 @@
 
 	rootflags=	[KNL] Set root filesystem mount option string
 
+	initramfs_options= [KNL]
+                        Specify mount options for for the initramfs mount.
+
 	rootfstype=	[KNL] Set root filesystem type
 
 	rootwait	[KNL] Wait (indefinitely) for root device to show up.

fs/namespace.c

@@ -65,6 +65,15 @@ static int __init set_mphash_entries(char *str)
 }
 __setup("mphash_entries=", set_mphash_entries);
 
+static char * __initdata initramfs_options;
+static int __init initramfs_options_setup(char *str)
+{
+	initramfs_options = str;
+	return 1;
+}
+
+__setup("initramfs_options=", initramfs_options_setup);
+
 static u64 event;
 static DEFINE_IDA(mnt_id_ida);
 static DEFINE_IDA(mnt_group_ida);
@@ -4311,7 +4320,7 @@ static void __init init_mount_tree(void)
 	struct mnt_namespace *ns;
 	struct path root;
 
-	mnt = vfs_kern_mount(&rootfs_fs_type, 0, "rootfs", NULL);
+	mnt = vfs_kern_mount(&rootfs_fs_type, 0, "rootfs", initramfs_options);
 	if (IS_ERR(mnt))
 		panic("Can't create rootfs");