linux-kernel - Re: [PATCH v2 0/4] make vmalloc gfp flags usage more apparent

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Message-ID: <aRYA1shUhLeof8d8@fedora>
Date: Thu, 13 Nov 2025 08:01:26 -0800
From: "Vishal Moola (Oracle)" <vishal.moola@...il.com>
To: Baolin Wang <baolin.wang@...ux.alibaba.com>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org, bpf@...r.kernel.org,
	Uladzislau Rezki <urezki@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Hellwig <hch@...radead.org>
Subject: Re: [PATCH v2 0/4] make vmalloc gfp flags usage more apparent

On Thu, Nov 13, 2025 at 11:48:05AM +0800, Baolin Wang wrote:
> Hi,
> 
> On 2025/11/13 02:58, Vishal Moola (Oracle) wrote:
> > We should do a better job at enforcing gfp flags for vmalloc. Right now, we
> > have a kernel-doc for __vmalloc_node_range(), and hope callers pass in
> > supported flags. If a caller were to pass in an unsupported flag, we may
> > BUG, silently clear it, or completely ignore it.
> > 
> > If we are more proactive about enforcing gfp flags, we can making sure
> > callers know when they may be asking for unsupported behavior.
> > 
> > This patchset lets vmalloc control the incoming gfp flags, and cleans up
> > some hard to read gfp code.
> > 
> > ---
> > Linked rfc [1] and rfc v2[2] for convenience.
> 
> Just FYI, I hit this warning when booting today's mm-new branch.
>
> [    1.238451] ------------[ cut here ]------------
> [    1.238453] Unexpected gfp: 0x400000 (__GFP_ACCOUNT). Fixing up to gfp:

Thanks. I'll send an updated version that catches this next week. In the
meantime, do let me know if you find any more warnings for other gfp
flags.

> 0xdc0 (GFP_KERNEL|__GFP_ZERO). Fix your code!
> [    1.249347] WARNING: CPU: 27 PID: 338 at mm/vmalloc.c:3937
> __vmalloc_noprof+0x74/0x80
> [    1.249352] Modules linked in:
> [    1.249354] CPU: 27 UID: 0 PID: 338 Comm: (journald) Not tainted
> 6.18.0-rc5+ #55 PREEMPT(none)
> [    1.249357] RIP: 0010:__vmalloc_noprof+0x74/0x80
> [    1.249359] Code: 00 5d e9 6f f8 ff ff 89 d1 49 89 e0 48 8d 54 24 04 89
> 74 24 04 81 e1 e0 ad 11 00 48 c7 c7 68 b0 75 82 89 0c 24 e8 7c bf ce ff <0f>
> 0b 8b 14 24 eb ab e8 f0 61 a5 00 90
>  90 90 90 90 90 90 90 90 90
> [    1.249360] RSP: 0018:ffffc90000bebe08 EFLAGS: 00010286
> [    1.249362] RAX: 0000000000000000 RBX: 0000000000001000 RCX:
> ffffffff82fdee68
> [    1.249363] RDX: 000000000000001b RSI: 0000000000000000 RDI:
> ffffffff82a5ee60
> [    1.249364] RBP: 0000000000001000 R08: 0000000000000000 R09:
> ffffc90000bebcb8
> [    1.249364] R10: ffffc90000bebcb0 R11: ffffffff8315eea8 R12:
> ffff88810aac98c0
> [    1.249365] R13: 0000000000000000 R14: ffffffff8141abe0 R15:
> fffffffffffffff3
> [    1.249368] FS:  00007fbc9436ee80(0000) GS:ffff88bec00e1000(0000)
> knlGS:0000000000000000
> [    1.249370] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [    1.249371] CR2: 0000562248eda010 CR3: 00000001028a8005 CR4:
> 0000000000770ef0
> [    1.249371] PKRU: 55555554
> [    1.249372] Call Trace:
> [    1.249373]  <TASK>
> [    1.249374]  bpf_prog_alloc_no_stats+0x37/0x250
> [    1.249377]  ? __pfx_seccomp_check_filter+0x10/0x10
> [    1.249379]  bpf_prog_alloc+0x1a/0xa0
> [    1.249381]  bpf_prog_create_from_user+0x51/0x130
> [    1.249385]  seccomp_set_mode_filter+0x117/0x410
> [    1.249387]  do_syscall_64+0x5b/0xda0
> [    1.249390]  entry_SYSCALL_64_after_hwframe+0x76/0x7e
> [    1.249392] RIP: 0033:0x7fbc94f4c9cd
>