From: Vlastimil Babka <vbabka@suse.cz>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org,
kasan-dev@googlegroups.com, Dmitry Vyukov <dvyukov@google.com>,
Marco Elver <elver@google.com>,
Vijayanand Jitta <vjitta@codeaurora.org>,
Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
Maxime Ripard <mripard@kernel.org>,
Thomas Zimmermann <tzimmermann@suse.de>,
David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>,
Andrey Ryabinin <ryabinin.a.a@gmail.com>,
Alexander Potapenko <glider@google.com>,
Andrey Konovalov <andreyknvl@gmail.com>,
Geert Uytterhoeven <geert@linux-m68k.org>,
Oliver Glitta <glittao@gmail.com>,
Imran Khan <imran.f.khan@oracle.com>,
Mike Rapoport <rppt@kernel.org>,
kernel test robot <oliver.sang@intel.com>
Subject: Re: [PATCH v3] lib/stackdepot: allow optional init and stack_table allocation by kvmalloc()
Date: Fri, 15 Oct 2021 10:57:13 +0200 [thread overview]
Message-ID: <6abd9213-19a9-6d58-cedc-2414386d2d81@suse.cz> (raw)
In-Reply-To: <20211013073005.11351-1-vbabka@suse.cz>
On 10/13/21 09:30, Vlastimil Babka wrote:
> Currently, enabling CONFIG_STACKDEPOT means its stack_table will be allocated
> from memblock, even if stack depot ends up not actually used. The default size
> of stack_table is 4MB on 32-bit, 8MB on 64-bit.
>
> This is fine for use-cases such as KASAN which is also a config option and
> has overhead on its own. But it's an issue for functionality that has to be
> actually enabled on boot (page_owner) or depends on hardware (GPU drivers)
> and thus the memory might be wasted. This was raised as an issue [1] when
> attempting to add stackdepot support for SLUB's debug object tracking
> functionality. It's common to build kernels with CONFIG_SLUB_DEBUG and enable
> slub_debug on boot only when needed, or create only specific kmem caches with
> debugging for testing purposes.
>
> It would thus be more efficient if stackdepot's table was allocated only when
> actually going to be used. This patch thus makes the allocation (and whole
> stack_depot_init() call) optional:
>
> - Add a CONFIG_STACKDEPOT_ALWAYS_INIT flag to keep using the current
> well-defined point of allocation as part of mem_init(). Make CONFIG_KASAN
> select this flag.
> - Other users have to call stack_depot_init() as part of their own init when
> it's determined that stack depot will actually be used. This may depend on
> both config and runtime conditions. Convert current users which are
> page_owner and several in the DRM subsystem. Same will be done for SLUB
> later.
> - Because the init might now be called after the boot-time memblock allocation
> has given all memory to the buddy allocator, change stack_depot_init() to
> allocate stack_table with kvmalloc() when memblock is no longer available.
> Also handle allocation failure by disabling stackdepot (could have
> theoretically happened even with memblock allocation previously), and don't
> unnecessarily align the memblock allocation to its own size anymore.
>
> [1] https://lore.kernel.org/all/CAMuHMdW=eoVzM1Re5FVoEN87nKfiLmM2+Ah7eNu2KXEhCvbZyA@mail.gmail.com/
...
> ---
> Changes in v3:
> - stack_depot_init_mutex made static and moved inside stack_depot_init()
> Reported-by: kernel test robot <lkp@intel.com>
> - use !stack_table condition instead of stack_table == NULL
> reported by checkpatch on freedesktop.org patchwork
The last change above was missing because I forgot git commit --amend before
git format-patch. More importantly there was a bot report for FLATMEM. Please
add this fixup. Thanks.
----8<----
From a971a1670491f8fbbaab579eef3c756a5263af95 Mon Sep 17 00:00:00 2001
From: Vlastimil Babka <vbabka@suse.cz>
Date: Thu, 7 Oct 2021 10:49:09 +0200
Subject: [PATCH] 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/
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: kernel test robot <oliver.sang@intel.com>
---
init/main.c | 7 +++++--
lib/stackdepot.c | 2 +-
2 files changed, 6 insertions(+), 3 deletions(-)
diff --git a/init/main.c b/init/main.c
index ca2765c8e45c..0ab632f681c5 100644
--- a/init/main.c
+++ b/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();
diff --git a/lib/stackdepot.c b/lib/stackdepot.c
index 049d7d025d78..1f8ea6d0899b 100644
--- a/lib/stackdepot.c
+++ b/lib/stackdepot.c
@@ -172,7 +172,7 @@ __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;
--
2.33.0
next prev parent reply other threads:[~2021-10-15 8:57 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-12 9:06 [PATCH v2] lib/stackdepot: allow optional init and stack_table allocation by kvmalloc() Vlastimil Babka
2021-10-12 9:57 ` Marco Elver
2021-10-12 21:52 ` kernel test robot
2021-10-12 21:52 ` [RFC PATCH] lib/stackdepot: stack_depot_init_mutex can be static kernel test robot
2021-10-13 7:30 ` [PATCH v3] lib/stackdepot: allow optional init and stack_table allocation by kvmalloc() Vlastimil Babka
2021-10-15 8:57 ` Vlastimil Babka [this message]
2021-10-14 8:54 ` [lib/stackdepot] 1cd8ce52c5: BUG:unable_to_handle_page_fault_for_address kernel test robot
2021-10-14 9:33 ` Vlastimil Babka
2021-10-14 10:16 ` Mike Rapoport
2021-10-15 8:27 ` Vlastimil Babka
2021-10-15 8:55 ` Mike Rapoport
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=6abd9213-19a9-6d58-cedc-2414386d2d81@suse.cz \
--to=vbabka@suse.cz \
--cc=airlied@linux.ie \
--cc=akpm@linux-foundation.org \
--cc=andreyknvl@gmail.com \
--cc=daniel@ffwll.ch \
--cc=dri-devel@lists.freedesktop.org \
--cc=dvyukov@google.com \
--cc=elver@google.com \
--cc=geert@linux-m68k.org \
--cc=glider@google.com \
--cc=glittao@gmail.com \
--cc=imran.f.khan@oracle.com \
--cc=intel-gfx@lists.freedesktop.org \
--cc=kasan-dev@googlegroups.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=maarten.lankhorst@linux.intel.com \
--cc=mripard@kernel.org \
--cc=oliver.sang@intel.com \
--cc=rppt@kernel.org \
--cc=ryabinin.a.a@gmail.com \
--cc=tzimmermann@suse.de \
--cc=vjitta@codeaurora.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).