Re: [PATCH] powerpc/modules: Don't WARN on first module allocation tentative

From: Christophe Leroy
Date: Tue Nov 30 2021 - 09:21:11 EST



Le 30/11/2021 à 15:06, Erhard F. a écrit :
On Tue, 30 Nov 2021 11:10:43 +0100
Christophe Leroy <christophe.leroy@xxxxxxxxxx> wrote:

module_alloc() first tries to allocate module text within
24 bits direct jump from kernel text, and tries a wider
allocation if first one fails.

When first allocation fails the following is observed in kernel logs:

vmap allocation for size 2400256 failed: use vmalloc=<size> to increase size
systemd-udevd: vmalloc error: size 2395133, vm_struct allocation failed, mode:0xcc0(GFP_KERNEL), nodemask=(null)
CPU: 0 PID: 127 Comm: systemd-udevd Tainted: G W 5.15.5-gentoo-PowerMacG4 #9
Call Trace:
[e2a53a50] [c0ba0048] dump_stack_lvl+0x80/0xb0 (unreliable)
[e2a53a70] [c0540128] warn_alloc+0x11c/0x2b4
[e2a53b50] [c0531be8] __vmalloc_node_range+0xd8/0x64c
[e2a53c10] [c00338c0] module_alloc+0xa0/0xac
[e2a53c40] [c027a368] load_module+0x2ae0/0x8148
[e2a53e30] [c027fc78] sys_finit_module+0xfc/0x130
[e2a53f30] [c0035098] ret_from_syscall+0x0/0x28
--- interrupt: c00 at 0x25df10
NIP: 0025df10 LR: 00416180 CTR: 00000000
REGS: e2a53f40 TRAP: 0c00 Tainted: G W (5.15.5-gentoo-PowerMacG4)
MSR: 0000d032 <EE,PR,ME,IR,DR,RI> CR: 2822242c XER: 20000000

GPR00: 00000161 afa8f060 a73a6160 00000011 0041dfa5 00000000 00000011 00000000
GPR08: 00000000 20000000 0000007a afa8efe0 002113f8 0072f924 00000000 00000000
GPR16: 00000005 afa8f1fc afa8f1e8 00000000 22222422 00000000 009603b0 22222422
GPR24: 00000000 00000000 0041dfa5 008a5fc0 00020000 00000000 00444cc4 009958f0
NIP [0025df10] 0x25df10
LR [00416180] 0x416180
--- interrupt: c00
Mem-Info:
active_anon:36 inactive_anon:4417 isolated_anon:0
active_file:3496 inactive_file:10535 isolated_file:0
unevictable:0 dirty:59 writeback:0
slab_reclaimable:3672 slab_unreclaimable:20540
mapped:5700 shmem:166 pagetables:185 bounce:0
kernel_misc_reclaimable:0
free:438282 free_pcp:1121 free_cma:0
Node 0 active_anon:144kB inactive_anon:17668kB active_file:13984kB inactive_file:42140kB unevictable:0kB isolated(anon):0kB isolated(file):0kB mapped:22800kB dirty:404kB writeback:0kB shmem:664kB writeback_tmp:0kB kernel_stack:1352kB pagetables:740kB all_unreclaimable? no
DMA free:267900kB min:2488kB low:3108kB high:3728kB reserved_highatomic:4096KB active_anon:0kB inactive_anon:0kB active_file:4016kB inactive_file:4224kB unevictable:0kB writepending:76kB present:524288kB managed:389432kB mlocked:0kB bounce:0kB free_pcp:2480kB local_pcp:1176kB free_cma:0kB
lowmem_reserve[]: 0 0 1536 1536
HighMem free:1485036kB min:512kB low:3032kB high:5552kB reserved_highatomic:0KB active_anon:136kB inactive_anon:17612kB active_file:9976kB inactive_file:37912kB unevictable:0kB writepending:364kB present:1572864kB managed:1572864kB mlocked:0kB bounce:0kB free_pcp:1776kB local_pcp:404kB free_cma:0kB
BTRFS: selftest: sectorsize: 4096 nodesize: 8192
lowmem_reserve[]: 0 0 0 0
BTRFS: selftest: running btrfs free space cache tests
DMA: 283*4kB (UMH) 282*8kB (UMH) 242*16kB (UMEH) 422*32kB (UMH) 187*64kB (UMH) 139*128kB (UME) 118*256kB (UM) 87*512kB (UME) 61*1024kB (UME) 27*2048kB (U) 6*4096kB (U) = 267612kB
BTRFS: selftest: running extent only tests
HighMem: 1*4kB (M) 1*8kB (M) 92*16kB (M) 43*32kB (UM) 21*64kB (M) 7*128kB (M) 3*256kB (UM) 1*512kB (U) 2*1024kB (UM) 1*2048kB (U) 360*4096kB (UM) = 1485036kB
BTRFS: selftest: running bitmap only tests
14218 total pagecache pages
0 pages in swap cache
Swap cache stats: add 0, delete 0, find 0/0
Free swap = 8388604kB
Total swap = 8388604kB
524288 pages RAM
393216 pages HighMem/MovableOnly
33714 pages reserved

Add __GFP_NOWARN flag to first allocation so that no warning appears
when it fails.

Reported-by: Erhard Furtner <erhard_f@xxxxxxxxxxx>
Fixes: 2ec13df16704 ("powerpc/modules: Load modules closer to kernel text")
Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
---
arch/powerpc/kernel/module.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/kernel/module.c b/arch/powerpc/kernel/module.c
index ed04a3ba66fe..40a583e9d3c7 100644
--- a/arch/powerpc/kernel/module.c
+++ b/arch/powerpc/kernel/module.c
@@ -90,16 +90,17 @@ int module_finalize(const Elf_Ehdr *hdr,
}
static __always_inline void *
-__module_alloc(unsigned long size, unsigned long start, unsigned long end)
+__module_alloc(unsigned long size, unsigned long start, unsigned long end, bool nowarn)
{
pgprot_t prot = strict_module_rwx_enabled() ? PAGE_KERNEL : PAGE_KERNEL_EXEC;
+ gfp_t gfp = GFP_KERNEL | (nowarn ? __GFP_NOWARN : 0);
/*
* Don't do huge page allocations for modules yet until more testing
* is done. STRICT_MODULE_RWX may require extra work to support this
* too.
*/
- return __vmalloc_node_range(size, 1, start, end, GFP_KERNEL, prot,
+ return __vmalloc_node_range(size, 1, start, end, gfp, prot,
VM_FLUSH_RESET_PERMS | VM_NO_HUGE_VMAP,
NUMA_NO_NODE, __builtin_return_address(0));
}
@@ -114,13 +115,13 @@ void *module_alloc(unsigned long size)
/* First try within 32M limit from _etext to avoid branch trampolines */
if (MODULES_VADDR < PAGE_OFFSET && MODULES_END > limit)
- ptr = __module_alloc(size, limit, MODULES_END);
+ ptr = __module_alloc(size, limit, MODULES_END, true);
if (!ptr)
- ptr = __module_alloc(size, MODULES_VADDR, MODULES_END);
+ ptr = __module_alloc(size, MODULES_VADDR, MODULES_END, false);
return ptr;
#else
- return __module_alloc(size, VMALLOC_START, VMALLOC_END);
+ return __module_alloc(size, VMALLOC_START, VMALLOC_END, false);
#endif
}
--
2.33.1

The patch applies on 5.15.5 but I still get this vmalloc error. Looks a bit different though:

[..]
Running code patching self-tests ...
vmap allocation for size 33562624 failed: use vmalloc=<size> to increase size
swapper/0: vmalloc error: size 33558528, vm_struct allocation failed, mode:0xcc0(GFP_KERNEL), nodemask=(null)
CPU: 0 PID: 1 Comm: swapper/0 Tainted: G W 5.15.5-PowerMacG4+ #2
Call Trace:
[f1033ba0] [c0b9fff0] dump_stack_lvl+0x80/0xb0 (unreliable)
[f1033bc0] [c05400d0] warn_alloc+0x11c/0x2b4
[f1033ca0] [c0531b90] __vmalloc_node_range+0xd8/0x64c
[f1033d60] [c05319a8] __vmalloc_node+0xec/0xf4
[f1033da0] [c1c0f998] test_code_patching+0x72c/0xd50

This one is something different.

The one I fixed with this patch is the one that was almost at the end of your dmesg, it was related to the loading of some module.

The one that remains comes from test_code_patching() and is a real failure that is due to LOWMEM being to high. This one should disappear when you reduce LOWMEM.

Christophe