On 12 May 2025, at 2:28, Zhang Yi wrote:
> From: Zhang Yi <yi.zhang@xxxxxxxxxx>
>
> When performing a right split on a folio, the split_at2 may point to a
> not-present page if the offset + length equals the original folio size,
> which will trigger the following error:
>
> BUG: unable to handle page fault for address: ffffea0006000008
> #PF: supervisor read access in kernel mode
> #PF: error_code(0x0000) - not-present page
> PGD 143ffb9067 P4D 143ffb9067 PUD 143ffb8067 PMD 0
> Oops: Oops: 0000 [#1] SMP PTI
> CPU: 0 UID: 0 PID: 502640 Comm: fsx Not tainted 6.15.0-rc3-gc6156189fc6b #889 PR
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-2.fc40 04/01/4
> RIP: 0010:truncate_inode_partial_folio+0x208/0x620
> Code: ff 03 48 01 da e8 78 7e 13 00 48 83 05 10 b5 5a 0c 01 85 c0 0f 85 1c 02 001
> RSP: 0018:ffffc90005bafab0 EFLAGS: 00010286
> RAX: 0000000000000000 RBX: ffffea0005ffff00 RCX: 0000000000000002
> RDX: 000000000000000c RSI: 0000000000013975 RDI: ffffc90005bafa30
> RBP: ffffea0006000000 R08: 0000000000000000 R09: 00000000000009bf
> R10: 00000000000007e0 R11: 0000000000000000 R12: 0000000000001633
> R13: 0000000000000000 R14: ffffea0005ffff00 R15: fffffffffffffffe
> FS: 00007f9f9a161740(0000) GS:ffff8894971fd000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: ffffea0006000008 CR3: 000000017c2ae000 CR4: 00000000000006f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
> <TASK>
> truncate_inode_pages_range+0x226/0x720
> truncate_pagecache+0x57/0x90
> ...
>
> Fix this issue by skipping the split if truncation aligns with the folio
> size, make sure the split page number lies within the folio.
>
> Fixes: 7460b470a131 ("mm/truncate: use folio_split() in truncate operation")
> Signed-off-by: Zhang Yi <yi.zhang@xxxxxxxxxx>
> ---
> mm/truncate.c | 20 ++++++++++++--------
> 1 file changed, 12 insertions(+), 8 deletions(-)
>
LGTM. Thank you for fixing it. Reviewed-by: Zi Yan <ziy@xxxxxxxxxx>
--
Best Regards,
Yan, Zi
