linux-kernel - Re: [PATCH v2 8/8] ext4: enable large folio for regular file

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Message-ID: <20250625131545.GD28249@mit.edu>
Date: Wed, 25 Jun 2025 09:15:45 -0400
From: "Theodore Ts'o" <tytso@....edu>
To: "Lai, Yi" <yi1.lai@...ux.intel.com>
Cc: Zhang Yi <yi.zhang@...weicloud.com>, linux-ext4@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        willy@...radead.org, adilger.kernel@...ger.ca, jack@...e.cz,
        yi.zhang@...wei.com, libaokun1@...wei.com, yukuai3@...wei.com,
        yangerkun@...wei.com, yi1.lai@...el.com
Subject: Re: [PATCH v2 8/8] ext4: enable large folio for regular file

It looks like this failure requires using madvise() with MADV_HWPOISON
(which requires root) and MADV_PAGEOUT, and the stack trace is in deep
in the an mm codepath:

   madvise_cold_or_pageout_pte_range+0x1cac/0x2800
      reclaim_pages+0x393/0x560
         reclaim_folio_list+0xe2/0x4c0
            shrink_folio_list+0x44f/0x3d90
                unmap_poisoned_folio+0x130/0x500
                    try_to_unmap+0x12f/0x140
                       rmap_walk+0x16b/0x1f0
		       ...

The bisected commit is the one which enables using large folios, so
while it's possible that this due to ext4 doing something not quite
right when using large folios, it's also posible that this might be a
bug in the folio/mm code paths.

Does this reproduce on other file systems, such as XFS?

     	  	       	     	  	   	- Ted