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Mon, 09 Mar 2026 13:42:58 -0700 (PDT) MIME-Version: 1.0 References: <5948f3a6-8f30-4c45-9b86-2af9a6b37405@kernel.org> <0dfd588c-3284-4310-b1cd-aab54567f0c0@kernel.org> <05a26f9d-e7eb-4aa4-b5a3-d485945f81c6@kernel.org> <5f4d8780-55f1-4b60-840a-056da7401848@kernel.org> In-Reply-To: From: Tytus Rogalewski Date: Mon, 9 Mar 2026 21:42:45 +0100 X-Gm-Features: AaiRm53pnBJFpu-WBS7SFotS4oseLbxWp-M9sxR5VJ49647nQCUgPzGZVTJWVSY Message-ID: Subject: Re: walk_pgd_range BUG: unable to handle page fault To: "David Hildenbrand (Arm)" Cc: linux-mm@kvack.org, muchun.song@linux.dev, osalvador@suse.de, Jens Axboe Content-Type: multipart/alternative; boundary="000000000000ba2660064c9d7236" X-Stat-Signature: kg9qb4yif11u3wiemrtpacehe6x6761s X-Rspam-User: X-Rspamd-Queue-Id: F30491C0002 X-Rspamd-Server: rspam12 X-HE-Tag: 1773088980-268053 X-HE-Meta: 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 /p1kr00R 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: --000000000000ba2660064c9d7236 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Hi, Well it seemed "like mem leak" but honestly it was my bad assumption i guess. And does it correlate with io_uring somehow ? Because i have no such issues when using threads mode in proxmox with network drive that is on fuse. Could be that triggered perhaps when someone was writing hard to his disk and that would cause other fuse drives to hung for few secs and that would trigger that BUG ? And using threads somehow fixes that issue ? Does that make any sense ? I am not familiar with low level memory management and io_uring too. -- tel. 790 202 300 *Tytus Rogalewski* Dolina Krzemowa 6A 83-010 Jagatowo NIP: 9570976234 pon., 9 mar 2026 o 21:27 David Hildenbrand (Arm) napisa=C5=82(a): > On 3/5/26 12:40, David Hildenbrand (Arm) wrote: > > On 3/5/26 12:39, Tytus Rogalewski wrote: > >> I had this problem on 6.19-rc4 yes. I saw it. But i cant reproduce it > >> NOW - this is what i ment :) > > > > Ah, thanks for clarifying, makes sense! > > > > The following issue might explain the problem: > > https://lore.kernel.org/r/20260309174949.2514565-1-mboone@akamai.com > > It would be related to what I recently said: "vfio recently gained > support for installing huge mappings into user page tables." > > smaps_walk_ops() does not have a pud_entry() callback, so we'd try to > split (unmap). If that happens concurrently with a refault, we might be > able to trigger a BUG. > > > But it wouldn't explain any memory leak. > > -- > Cheers, > > David > --000000000000ba2660064c9d7236 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Hi,

Well it seemed "lik= e mem leak" but honestly it was my bad assumption=C2=A0i guess.
<= div>
And does it correlate=C2=A0with io_uring somehow ?
=
Because=C2=A0i have no such issues when using threads mode in proxmox = with network=C2=A0drive that is on fuse.
Could be that triggered perhaps= when someone was writing hard to his disk and that would cause other fuse = drives to hung for few secs and that would trigger that BUG ?
And= using threads somehow fixes that issue ? Does that make any sense ? I am n= ot familiar with low level memory management and io_uring too.


--

tel. 790 202 300

Tytus Rogalewski

Dolina Krzemowa 6A<= /font>

83-010 Jagatowo

NIP: 9570976234



pon., 9 mar 2026 o 21= :27=C2=A0David Hildenbrand (Arm) <da= vid@kernel.org> napisa=C5=82(a):
On 3/5/26 12:40, David Hildenbrand (Arm) wrote:
> On 3/5/26 12:39, Tytus Rogalewski wrote:
>> I had this problem on 6.19-rc4 yes. I saw it. But i cant=C2=A0repr= oduce it
>> NOW - this is what i ment=C2=A0 :)
>
> Ah, thanks for clarifying, makes sense!
>

The following issue might explain the problem:

https://lore.kernel.org/r/202603= 09174949.2514565-1-mboone@akamai.com

It would be related to what I recently said: "vfio recently gained
support for installing huge mappings into user page tables."

smaps_walk_ops() does not have a pud_entry() callback, so we'd try to split (unmap). If that happens concurrently with a refault, we might be
able to trigger a BUG.


But it wouldn't explain any memory leak.

--
Cheers,

David
--000000000000ba2660064c9d7236--