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Message-ID: <e360598c-cb58-cf9d-9247-430b8df9b3b7@huawei.com>
Date: Thu, 22 Aug 2024 16:04:10 +0800
From: Miaohe Lin <linmiaohe@...wei.com>
To: Hao Ge <hao.ge@...ux.dev>
CC: <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>, Hao Ge
<gehao@...inos.cn>, <stable@...r.kernel.org>, <nao.horiguchi@...il.com>,
<akpm@...ux-foundation.org>, <surenb@...gle.com>,
<pasha.tatashin@...een.com>, <david@...hat.com>, <kent.overstreet@...ux.dev>
Subject: Re: [PATCH] codetag: debug: mark codetags for pages which
transitioned from being poison to unpoison as empty
On 2024/8/22 10:58, Hao Ge wrote:
> From: Hao Ge <gehao@...inos.cn>
>
Thanks for your patch.
> The PG_hwpoison page will be caught and isolated on the entrance to
> the free buddy page pool. so,when we clear this flag and return it
> to the buddy system,mark codetags for pages as empty.
>
Is below scene cause the problem?
1. Pages are allocated. pgalloc_tag_add() will be called when prep_new_page().
2. Pages are hwpoisoned. memory_failure() will set PG_hwpoison flag and pgalloc_tag_sub()
will be called when pages are caught and isolated on the entrance to buddy.
3. unpoison_memory cleared flags and sent the pages to buddy. pgalloc_tag_sub() will be
called again in free_pages_prepare().
So there is a imbalance that pgalloc_tag_add() is called once and pgalloc_tag_sub() is called twice?
If so, let's think about more complicated scene:
1. Same as above.
2. Pages are hwpoisoned. But memory_failure() fails to handle it. So PG_hwpoison flag is set
but pgalloc_tag_sub() is not called (pages are not sent to buddy).
3. unpoison_memory cleared flags and calls clear_page_tag_ref() without calling pgalloc_tag_sub()
first. Will this cause problem?
Though this should be really rare...
Thanks.
.
> It was detected by [1] and the following WARN occurred:
>
> [ 113.930443][ T3282] ------------[ cut here ]------------
> [ 113.931105][ T3282] alloc_tag was not set
> [ 113.931576][ T3282] WARNING: CPU: 2 PID: 3282 at ./include/linux/alloc_tag.h:130 pgalloc_tag_sub.part.66+0x154/0x164
> [ 113.932866][ T3282] Modules linked in: hwpoison_inject fuse ip6t_rpfilter ip6t_REJECT nf_reject_ipv6 ipt_REJECT nf_reject_ipv4 xt_conntrack ebtable_nat ebtable_broute ip6table_nat ip6table_man4
> [ 113.941638][ T3282] CPU: 2 UID: 0 PID: 3282 Comm: madvise11 Kdump: loaded Tainted: G W 6.11.0-rc4-dirty #18
> [ 113.943003][ T3282] Tainted: [W]=WARN
> [ 113.943453][ T3282] Hardware name: QEMU KVM Virtual Machine, BIOS unknown 2/2/2022
> [ 113.944378][ T3282] pstate: 40400005 (nZcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> [ 113.945319][ T3282] pc : pgalloc_tag_sub.part.66+0x154/0x164
> [ 113.946016][ T3282] lr : pgalloc_tag_sub.part.66+0x154/0x164
> [ 113.946706][ T3282] sp : ffff800087093a10
> [ 113.947197][ T3282] x29: ffff800087093a10 x28: ffff0000d7a9d400 x27: ffff80008249f0a0
> [ 113.948165][ T3282] x26: 0000000000000000 x25: ffff80008249f2b0 x24: 0000000000000000
> [ 113.949134][ T3282] x23: 0000000000000001 x22: 0000000000000001 x21: 0000000000000000
> [ 113.950597][ T3282] x20: ffff0000c08fcad8 x19: ffff80008251e000 x18: ffffffffffffffff
> [ 113.952207][ T3282] x17: 0000000000000000 x16: 0000000000000000 x15: ffff800081746210
> [ 113.953161][ T3282] x14: 0000000000000000 x13: 205d323832335420 x12: 5b5d353031313339
> [ 113.954120][ T3282] x11: ffff800087093500 x10: 000000000000005d x9 : 00000000ffffffd0
> [ 113.955078][ T3282] x8 : 7f7f7f7f7f7f7f7f x7 : ffff80008236ba90 x6 : c0000000ffff7fff
> [ 113.956036][ T3282] x5 : ffff000b34bf4dc8 x4 : ffff8000820aba90 x3 : 0000000000000001
> [ 113.956994][ T3282] x2 : ffff800ab320f000 x1 : 841d1e35ac932e00 x0 : 0000000000000000
> [ 113.957962][ T3282] Call trace:
> [ 113.958350][ T3282] pgalloc_tag_sub.part.66+0x154/0x164
> [ 113.959000][ T3282] pgalloc_tag_sub+0x14/0x1c
> [ 113.959539][ T3282] free_unref_page+0xf4/0x4b8
> [ 113.960096][ T3282] __folio_put+0xd4/0x120
> [ 113.960614][ T3282] folio_put+0x24/0x50
> [ 113.961103][ T3282] unpoison_memory+0x4f0/0x5b0
> [ 113.961678][ T3282] hwpoison_unpoison+0x30/0x48 [hwpoison_inject]
> [ 113.962436][ T3282] simple_attr_write_xsigned.isra.34+0xec/0x1cc
> [ 113.963183][ T3282] simple_attr_write+0x38/0x48
> [ 113.963750][ T3282] debugfs_attr_write+0x54/0x80
> [ 113.964330][ T3282] full_proxy_write+0x68/0x98
> [ 113.964880][ T3282] vfs_write+0xdc/0x4d0
> [ 113.965372][ T3282] ksys_write+0x78/0x100
> [ 113.965875][ T3282] __arm64_sys_write+0x24/0x30
> [ 113.966440][ T3282] invoke_syscall+0x7c/0x104
> [ 113.966984][ T3282] el0_svc_common.constprop.1+0x88/0x104
> [ 113.967652][ T3282] do_el0_svc+0x2c/0x38
> [ 113.968893][ T3282] el0_svc+0x3c/0x1b8
> [ 113.969379][ T3282] el0t_64_sync_handler+0x98/0xbc
> [ 113.969980][ T3282] el0t_64_sync+0x19c/0x1a0
> [ 113.970511][ T3282] ---[ end trace 0000000000000000 ]---
>
> Link [1]: https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/syscalls/madvise/madvise11.c
>
> Fixes: a8fc28dad6d5 ("alloc_tag: introduce clear_page_tag_ref() helper function")
> Cc: stable@...r.kernel.org # v6.10
> Signed-off-by: Hao Ge <gehao@...inos.cn>
> ---
> mm/memory-failure.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 7066fc84f351..570388c41532 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -2623,6 +2623,12 @@ int unpoison_memory(unsigned long pfn)
>
> folio_put(folio);
> if (TestClearPageHWPoison(p)) {
> + /* the PG_hwpoison page will be caught and isolated
> + * on the entrance to the free buddy page pool.
> + * so,when we clear this flag and return it to the buddy system,
> + * clear it's codetag
> + */
> + clear_page_tag_ref(p);
> folio_put(folio);
> ret = 0;
> }
>
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