+ lib-stackdepot-allow-optional-init-and-stack_table-allocation-by-kvmalloc-fix-2.patch added to -mm tree

+ lib-stackdepot-allow-optional-init-and-stack_table-allocation-by-kvmalloc-fix-2.patch added to -mm tree

[akpm]

The patch titled
     Subject: lib/stackdepot: allow optional init and stack_table allocation by kvmalloc() - fixup
has been added to the -mm tree.  Its filename is
     lib-stackdepot-allow-optional-init-and-stack_table-allocation-by-kvmalloc-fix-2.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/lib-stackdepot-allow-optional-init-and-stack_table-allocation-by-kvmalloc-fix-2.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/lib-stackdepot-allow-optional-init-and-stack_table-allocation-by-kvmalloc-fix-2.patch

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------------------------------------------------------
From: Vlastimil Babka <vbabka@suse.cz>
Subject: lib/stackdepot: allow optional init and stack_table allocation by kvmalloc() - fixup

On FLATMEM, we call page_ext_init_flatmem_late() just before
kmem_cache_init() which means stack_depot_init() (called by page owner
init) will not recognize properly it should use kvmalloc() and not
memblock_alloc().  memblock_alloc() will also not issue a warning and
return a block memory that can be invalid and cause kernel page fault when
saving stacks, as reported by the kernel test robot [1].

Fix this by moving page_ext_init_flatmem_late() below kmem_cache_init() so
that slab_is_available() is true during stack_depot_init().  SPARSEMEM
doesn't have this issue, as it doesn't do page_ext_init_flatmem_late(),
but a different page_ext_init() even later in the boot process.

Thanks to Mike Rapoport for pointing out the FLATMEM init ordering issue.

While at it, also actually resolve a checkpatch warning in stack_depot_init()
from DRM CI, which was supposed to be in the original patch already.

[1] https://lore.kernel.org/all/20211014085450.GC18719@xsang-OptiPlex-9020/

Link: https://lkml.kernel.org/r/6abd9213-19a9-6d58-cedc-2414386d2d81@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: kernel test robot <oliver.sang@intel.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 init/main.c      |    7 +++++--
 lib/stackdepot.c |    2 +-
 2 files changed, 6 insertions(+), 3 deletions(-)

--- a/init/main.c~lib-stackdepot-allow-optional-init-and-stack_table-allocation-by-kvmalloc-fix-2
+++ a/init/main.c
@@ -845,9 +845,12 @@ static void __init mm_init(void)
 	stack_depot_early_init();
 	mem_init();
 	mem_init_print_info();
-	/* page_owner must be initialized after buddy is ready */
-	page_ext_init_flatmem_late();
 	kmem_cache_init();
+	/*
+	 * page_owner must be initialized after buddy is ready, and also after
+	 * slab is ready so that stack_depot_init() works properly
+	 */
+	page_ext_init_flatmem_late();
 	kmemleak_init();
 	pgtable_init();
 	debug_objects_mem_init();
--- a/lib/stackdepot.c~lib-stackdepot-allow-optional-init-and-stack_table-allocation-by-kvmalloc-fix-2
+++ a/lib/stackdepot.c
@@ -171,7 +171,7 @@ __ref int stack_depot_init(void)
 	static DEFINE_MUTEX(stack_depot_init_mutex);
 
 	mutex_lock(&stack_depot_init_mutex);
-	if (!stack_depot_disable && stack_table == NULL) {
+	if (!stack_depot_disable && !stack_table) {
 		size_t size = (STACK_HASH_SIZE * sizeof(struct stack_record *));
 		int i;
 
_

Patches currently in -mm which might be from vbabka@suse.cz are

lib-stackdepot-allow-optional-init-and-stack_table-allocation-by-kvmalloc.patch
lib-stackdepot-allow-optional-init-and-stack_table-allocation-by-kvmalloc-fix-2.patch