[PATCH v5] vmalloc: Modify the alloc_vmap_area() error message for better diagnostics

[Shubhang Kaushik OS]

Okay, will follow that protocol. This update is to replace the vmalloc range parameters in the overflow warning message to be between vstart and vend.

________________________________________
From: Andrew Morton <akpm at linux-foundation.org>
Sent: Tuesday, June 11, 2024 12:57 PM
To: Shubhang Kaushik OS
Cc: ampere-linux-kernel at lists.amperecomputing.com; Uladzislau Rezki; linux-arm-kernel at lists.infradead.org; cl at linux.com; corbet at lwn.net; linux-mm at kvack.org; guoren at kernel.org; linux-doc at vger.kernel.org; xiongwei.song at windriver.com; linux-riscv at lists.infradead.org; linux-csky at vger.kernel.org; Matthew Wilcox
Subject: Re: [PATCH v5] vmalloc: Modify the alloc_vmap_area() error message for better diagnostics

On Tue, 11 Jun 2024 19:38:44 +0000 Shubhang Kaushik OS <Shubhang at os.amperecomputing.com> wrote:

> 'vmap allocation for size %lu failed: use vmalloc=<size> to increase size'
> The above warning is seen in the kernel functionality for allocation of the restricted virtual memory range till exhaustion.
>
> This message is misleading because 'vmalloc=' is supported on arm32, x86 platforms and is not a valid kernel parameter on a number of other platforms (in particular its not supported on arm64, alpha, loongarch, arc, csky, hexagon, microblaze, mips, nios2, openrisc, parisc, m64k, powerpc, riscv, sh, um, xtensa, s390, sparc). With the update, the output gets modified to include the function parameters along with the start and end of the virtual memory range allowed.
>
> The warning message after fix on kernel version 6.10.0-rc1+:
>
> vmalloc_node_range for size 33619968 failed: Address range restricted between 0xffff800082640000 - 0xffff800084650000
>
> Backtrace with the misleading error message:
>
>       vmap allocation for size 33619968 failed: use vmalloc=<size> to increase size
>       insmod: vmalloc error: size 33554432, vm_struct allocation failed, mode:0xcc0(GFP_KERNEL), nodemask=(null),cpuset=/,mems_allowed=0
>       CPU: 46 PID: 1977 Comm: insmod Tainted: G            E      6.10.0-rc1+ #79
>       Hardware name: INGRASYS Yushan Server iSystem TEMP-S000141176+10/Yushan Motherboard, BIOS 2.10.20230517 (SCP: xxx) yyyy/mm/dd
>       Call trace:
>               dump_backtrace+0xa0/0x128
>               show_stack+0x20/0x38
>               dump_stack_lvl+0x78/0x90
>               dump_stack+0x18/0x28
>               warn_alloc+0x12c/0x1b8
>               __vmalloc_node_range_noprof+0x28c/0x7e0
>               custom_init+0xb4/0xfff8 [test_driver]
>               do_one_initcall+0x60/0x290
>               do_init_module+0x68/0x250
>               load_module+0x236c/0x2428
>               init_module_from_file+0x8c/0xd8
>               __arm64_sys_finit_module+0x1b4/0x388
>               invoke_syscall+0x78/0x108
>               el0_svc_common.constprop.0+0x48/0xf0
>               do_el0_svc+0x24/0x38
>               el0_svc+0x3c/0x130
>               el0t_64_sync_handler+0x100/0x130
>               el0t_64_sync+0x190/0x198

When sending an updated version, please describe what was changed since
the previous version.  After the changelog's ^---$ separator is the
usual place.

I'm seeing this:

--- a/mm/vmalloc.c~vmalloc-modify-the-alloc_vmap_area-error-message-for-better-diagnostics-v5
+++ a/mm/vmalloc.c
@@ -2057,7 +2057,7 @@ overflow:

        if (!(gfp_mask & __GFP_NOWARN) && printk_ratelimit())
                pr_warn("vmalloc_node_range for size %lu failed: Address range restricted to %#lx - %#lx\n",
-                               size, addr, addr+size);
+                               size, vstart, vend);

        kmem_cache_free(vmap_area_cachep, va);
        return ERR_PTR(-EBUSY);
_

which I assume has no effect?