linux-kernel - Re: Known and unfixed active data loss bug in MM + XFS with large folios since Dec 2021 (any kernel from 6.1 upwards)

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Message-ID: <8148432d-5865-49a2-affb-71fe79df2e4e@meta.com>
Date: Wed, 18 Sep 2024 14:23:35 +0200
From: Chris Mason <clm@...a.com>
To: Jens Axboe <axboe@...nel.dk>, Matthew Wilcox <willy@...radead.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
        Dave Chinner <david@...morbit.com>,
        Christian Theune <ct@...ingcircus.io>, linux-mm@...ck.org,
        "linux-xfs@...r.kernel.org" <linux-xfs@...r.kernel.org>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Daniel Dao <dqminh@...udflare.com>, regressions@...ts.linux.dev,
        regressions@...mhuis.info
Subject: Re: Known and unfixed active data loss bug in MM + XFS with large
 folios since Dec 2021 (any kernel from 6.1 upwards)

On 9/18/24 5:28 AM, Chris Mason wrote:
> And I attached radixcheck.py if you want to see the full script.

Since the attachment didn't actually make it through:

#!/usr/bin/env -S drgn -c vmcore

from drgn.helpers.linux.fs import *
from drgn.helpers.linux.mm import *
from drgn.helpers.linux.list import *
from drgn.helpers.linux.xarray import *
from drgn import *
import os
import sys
import time

mapping = Object(prog, 'struct  address_space', address=0xffff88a22a9614e8)
#p = path_lookup(prog, sys.argv[1]);
#mapping = p.dentry.d_inode.i_mapping

for index, x in xa_for_each(mapping.i_pages.address_of_()):
    if xa_is_zero(x):
        continue
    if xa_is_value(x):
        continue

    page = Object(prog, 'struct page', address=x)
    folio = Object(prog, 'struct folio', address=x)

    print("0x%x mapping 0x%x radix index %d page index %d flags 0x%x (%s) size %d" % (page.address_of_(), page.mapping.value_(), index, page.index, page.flags, decode_page_flags(page), folio._folio_nr_pages))