Merge branches 'expcb.2026.07.24a', 'misc.2026.07.30a', 'rcu-tasks.2026.07.30a', 'srcu.2026.08.11a' and 'torture.2026.08.14a' into HEADgrafted

Changes:

Make expedited grace periods expedite normal RCU callbacks

Miscellaneous fixes:
 * Improve diagnostic output with character task states.
 * Mark accesses to inform KCSAN of concurrency design.
 * Move from kmalloc() to kmalloc_obj().
 * Documentation updates.
 * Improve handling of RCU deferred quiescent states.
 * Clean up unused function arguments and structure fields.
 * Reduce show_rcu_gp_kthreads() stack space.

Tasks RCU updates:
 * Clean up after SRCU re-implementation of Tasks Trace RCU.
 * Mark accesses to inform KCSAN of concurrency design.
 * Add ->lazy_timer status to diagnostic output.
 * Remove an unnecessary memory barrier.
 * Fix a data race, courtesy of KCSAN.
 * Documentation updates.
 * Convert cond_resched_tasks_rcu_qs() from macro to static inline
   function.

SRCU updates:
 * Add Rust helpers for SRCU.
 * Avoid losing queued work at cleanup_srcu_struct() time.

Torture-test updates:
 * Preparation work for immediate RCU priority deboosting.
 * Test RCU readers from real interrupt handlers (as opposed to softirq).
 * Simplify code through use of cpumask_next_wrap().
 * Improve diagnostic output with character task states.
 * Add rcutorture.nwriters parameter to allow lightweight stall testing,
   and rcutorture.stall_only to make doing so easier.
 * Test an RCU Tasks Trace grace period implying an RCU grace period.
 * Make RCU Tasks Trace torturing track reader batches.
 * Fix a data race, courtesy of KCSAN.
 * Plug a shuffle_tmp_mask memory leak on kthread spawn failure.

1 files changed, 80 insertions, 0 deletions

diff --git a/drivers/mtd/mtdblock_ro.c b/drivers/mtd/mtdblock_ro.c
new file mode 100644
index 000000000..e564521d6
--- /dev/null
+++ b/drivers/mtd/mtdblock_ro.c
@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Simple read-only (writable only for RAM) mtdblock driver
+ *
+ * Copyright © 2001-2010 David Woodhouse <dwmw2@infradead.org>
+ */
+
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/mtd/mtd.h>
+#include <linux/mtd/blktrans.h>
+#include <linux/module.h>
+#include <linux/major.h>
+
+static int mtdblock_readsect(struct mtd_blktrans_dev *dev,
+			      unsigned long block, char *buf)
+{
+	size_t retlen;
+	int err;
+
+	err = mtd_read(dev->mtd, (block * 512), 512, &retlen, buf);
+	if (err && !mtd_is_bitflip(err))
+		return 1;
+	return 0;
+}
+
+static int mtdblock_writesect(struct mtd_blktrans_dev *dev,
+			      unsigned long block, char *buf)
+{
+	size_t retlen;
+
+	if (mtd_write(dev->mtd, (block * 512), 512, &retlen, buf))
+		return 1;
+	return 0;
+}
+
+static void mtdblock_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
+{
+	struct mtd_blktrans_dev *dev = kzalloc_obj(*dev);
+
+	if (!dev)
+		return;
+
+	dev->mtd = mtd;
+	dev->devnum = mtd->index;
+
+	dev->size = mtd->size >> 9;
+	dev->tr = tr;
+	dev->readonly = 1;
+
+	if (mtd_type_is_nand(mtd))
+		pr_warn_ratelimited("%s: MTD device '%s' is NAND, please consider using UBI block devices instead.\n",
+			tr->name, mtd->name);
+
+	if (add_mtd_blktrans_dev(dev))
+		kfree(dev);
+}
+
+static void mtdblock_remove_dev(struct mtd_blktrans_dev *dev)
+{
+	del_mtd_blktrans_dev(dev);
+}
+
+static struct mtd_blktrans_ops mtdblock_tr = {
+	.name		= "mtdblock",
+	.major		= MTD_BLOCK_MAJOR,
+	.part_bits	= 0,
+	.blksize 	= 512,
+	.readsect	= mtdblock_readsect,
+	.writesect	= mtdblock_writesect,
+	.add_mtd	= mtdblock_add_mtd,
+	.remove_dev	= mtdblock_remove_dev,
+	.owner		= THIS_MODULE,
+};
+
+module_mtd_blktrans(mtdblock_tr);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("David Woodhouse <dwmw2@infradead.org>");
+MODULE_DESCRIPTION("Simple read-only block device emulation access to MTD devices");