Re: [PATCH 0/3 v3] ARM/ARM64: silence large module first time allocation

[Florian Fainelli]

On 04/27/2017 11:24 AM, Ard Biesheuvel wrote:
> 
>> On 27 Apr 2017, at 19:18, Florian Fainelli <f.fainelli@xxxxxxxxx> wrote:
>>
>> With kernels built with CONFIG_ARM{,64}_MODULES_PLTS=y, the first allocation
>> done from module space will fail, produce a general OOM allocation and also a
>> vmap warning. The second allocation from vmalloc space may or may not be
>> successful, but is actually the one we are interested about in these cases.
>>
>> This patch series passed __GFP_NOWARN to silence such allocations from the
>> ARM/ARM64 module loader's first time allocation when the MODULES_PLT option is
>> enabled, and also makes alloc_vmap_area() react to the caller setting
>> __GFP_NOWARN to silence "vmap allocation for size..." messages.
>>
>>
>> Changes in v3:
>> - check for __GFP_NOWARN not set where the check for printk_ratelimited()
>>  is done, add Michal's Acked-by
>>
>> - use C conditionals and not CPP conditionals for IS_ENABLED(), add Ard's
>>  Reviewed-by tag
>>
> 
> Ok these look fine now. But are you sure that omitting the single pr_warn() gets rid of all of that?
> Or do we need more patches on top?

Since the caller now set __GFP_NOWARN, this propagates correctly to all
functions called from alloc_vmap_area() like kmalloc_node(). With the
patches applied, I only get the stuff that I would expect:

# echo 8 7 4 1 > /proc/sys/kernel/printk
# insmod huge.ko
[   59.285547] huge: loading out-of-tree module taints kernel.
[   59.328553] big_init: I am a big module using 3932160 bytes of data!
#

> 
> 
>> Changes in v2:
>>
>> - check __GFP_NOWARN out of the printk_ratelimited() check (Michal)
>>
>> Here is an example of what we would get without these two patches, pretty
>> scary huh?
>>
>> # insmod /mnt/nfs/huge.ko 
>> [   22.114143] random: nonblocking pool is initialized
>> [   22.183575] vmap allocation for size 15736832 failed: use vmalloc=<size> to increase size.
>> [   22.191873] vmalloc: allocation failure: 15729534 bytes
>> [   22.197112] insmod: page allocation failure: order:0, mode:0xd0
>> [   22.203048] CPU: 2 PID: 1506 Comm: insmod Tainted: G           O    4.1.20-1.9pre-01082-gbbbff07bc3ce #9
>> [   22.212536] Hardware name: Broadcom STB (Flattened Device Tree)
>> [   22.218480] [<c0017eec>] (unwind_backtrace) from [<c00135c8>] (show_stack+0x10/0x14)
>> [   22.226238] [<c00135c8>] (show_stack) from [<c0638684>] (dump_stack+0x90/0xa4)
>> [   22.233473] [<c0638684>] (dump_stack) from [<c00aae1c>] (warn_alloc_failed+0x104/0x144)
>> [   22.241490] [<c00aae1c>] (warn_alloc_failed) from [<c00d72e0>] (__vmalloc_node_range+0x170/0x218)
>> [   22.250375] [<c00d72e0>] (__vmalloc_node_range) from [<c00147d0>] (module_alloc+0x50/0xac)
>> [   22.258651] [<c00147d0>] (module_alloc) from [<c008ae2c>] (module_alloc_update_bounds+0xc/0x6c)
>> [   22.267360] [<c008ae2c>] (module_alloc_update_bounds) from [<c008b778>] (load_module+0x8ec/0x2058)
>> [   22.276329] [<c008b778>] (load_module) from [<c008cfd4>] (SyS_init_module+0xf0/0x174)
>> [   22.284170] [<c008cfd4>] (SyS_init_module) from [<c0010140>] (ret_fast_syscall+0x0/0x3c)
>> [   22.292277] Mem-Info:
>> [   22.294567] active_anon:5236 inactive_anon:1773 isolated_anon:0
>> [   22.294567]  active_file:1 inactive_file:3822 isolated_file:0
>> [   22.294567]  unevictable:0 dirty:0 writeback:0 unstable:0
>> [   22.294567]  slab_reclaimable:238 slab_unreclaimable:1594
>> [   22.294567]  mapped:855 shmem:2950 pagetables:36 bounce:0
>> [   22.294567]  free:39031 free_pcp:198 free_cma:3928
>> [   22.327196] DMA free:156124kB min:1880kB low:2348kB high:2820kB active_anon:20944kB inactive_anon:7092kB active_file:4kB inactive_file:15288kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:262144kB managed:227676kB mlocked:0kB dirty:0kB writeback:0kB mapped:3420kB shmem:11800kB slab_reclaimable:952kB slab_unreclaimable:6376kB kernel_stack:560kB pagetables:144kB unstable:0kB bounce:0kB free_pcp:792kB local_pcp:68kB free_cma:15712kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no
>> [   22.371631] lowmem_reserve[]: 0 0 0 0
>> [   22.375372] HighMem free:0kB min:128kB low:128kB high:128kB active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:2883584kB managed:0kB mlocked:0kB dirty:0kB writeback:0kB mapped:0kB shmem:0kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB pagetables:0kB unstable:0kB bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? yes
>> [   22.416249] lowmem_reserve[]: 0 0 0 0
>> [   22.419986] DMA: 3*4kB (UEM) 4*8kB (UE) 1*16kB (M) 4*32kB (UEMC) 3*64kB (EMC) 1*128kB (E) 4*256kB (UEMC) 2*512kB (UE) 2*1024kB (MC) 4*2048kB (UEMC) 35*4096kB (MRC) = 156156kB
>> [   22.435922] HighMem: 0*4kB 0*8kB 0*16kB 0*32kB 0*64kB 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 0kB
>> [   22.446130] 6789 total pagecache pages
>> [   22.449889] 0 pages in swap cache
>> [   22.453212] Swap cache stats: add 0, delete 0, find 0/0
>> [   22.458447] Free swap  = 0kB
>> [   22.461334] Total swap = 0kB
>> [   22.464222] 786432 pages RAM
>> [   22.467110] 720896 pages HighMem/MovableOnly
>> [   22.471388] 725417 pages reserved
>> [   22.474711] 4096 pages cma reserved
>> [   22.511310] big_init: I am a big module using 3932160 bytes of data!
>>
>> Florian Fainelli (3):
>>  mm: Silence vmap() allocation failures based on caller gfp_flags
>>  ARM: Silence first allocation with CONFIG_ARM_MODULE_PLTS=y
>>  arm64: Silence first allocation with CONFIG_ARM64_MODULE_PLTS=y
>>
>> arch/arm/kernel/module.c   | 11 +++++++++--
>> arch/arm64/kernel/module.c |  7 ++++++-
>> mm/vmalloc.c               |  2 +-
>> 3 files changed, 16 insertions(+), 4 deletions(-)
>>
>> -- 
>> 2.9.3
>>


-- 
Florian