Hi Matthew,
There is a strange warning on bootup related to folios. Seen it a couple
of times before. Why does this occur?
Activating swap
20.765039] ------------[ cut here ]------------
[ 20.772475] WARNING: CPU: 35 PID: 1152 at mm/page_alloc.c:2774 get_page_from_freelist+0x214/0x17f8
[ 20.784194] Modules linked in:
[ 20.784197] CPU: 35 PID: 1152 Comm: swapon Not tainted 6.6.0-base #109
[ 20.784202] Hardware name: WIWYNN Mt.Jade Server System B81.03001.0014/Mt.Jade Motherboard, BIOS 2.10.20230517 (SCP: 2.10.20230517) 2023/05/17
[ 20.808072] pstate: 20400009 (nzCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[ 20.808075] pc : get_page_from_freelist+0x214/0x17f8
[ 20.808080] lr : get_page_from_freelist+0xaa8/0x17f8
[ 20.808084] sp : ffff800094623510
[ 20.808085] x29: ffff800094623510 x28: 0000000000000000 x27: ffff083f7fffe700
[ 20.808089] x26: 0000000000000000 x25: 0000000000000004 x24: ffff083f7fffe700
[ 20.808093] x23: ffff083f7fffe700 x22: 0000000000012dd8 x21: ffff8000828cf000
[ 20.808096] x20: 0000000000000002 x19: 0000000000000801 x18: 0000000000000000
[ 20.808100] x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000
[ 20.808102] x14: 0000000000000000 x13: ffff07ff917f0c7b x12: 0000000000000005
[ 20.808105] x11: 0000000000000000 x10: ffff083f7fffe8f0 x9 : 0000000000000000
[ 20.808108] x8 : ffff083f7fffe8e0 x7 : ffff083f7fffe8d0 x6 : ffff083f7fffe700
[ 20.878104] x5 : ffff083f7fffe910 x4 : fffffc1fff3e1708 x3 : ffff083f7fffe900
[ 20.878107] x2 : ffff083f7fffe7d0 x1 : ffff800094623710 x0 : 0000000000008000
[ 20.878110] Call trace:
[ 20.878111] get_page_from_freelist+0x214/0x17f8
[ 20.878116] __alloc_pages+0x17c/0xe08
[ 20.878120] __kmalloc_large_node+0xa0/0x170
[ 20.878123] __kmalloc_node+0x120/0x1d0
[ 20.878125] memcg_alloc_slab_cgroups+0x48/0xc0
[ 20.878128] memcg_slab_post_alloc_hook+0xa8/0x1c8
[ 20.878132] kmem_cache_alloc+0x18c/0x338
[ 20.878135] alloc_buffer_head+0x28/0xa0
[ 20.878138] folio_alloc_buffers+0xe8/0x1c0
[ 20.878141] folio_create_empty_buffers+0x2c/0x1e8
[ 20.878143] folio_create_buffers+0x58/0x80
[ 20.878145] block_read_full_folio+0x80/0x450
[ 20.878148] blkdev_read_folio+0x24/0x38
[ 20.956921] filemap_read_folio+0x60/0x138
[ 20.956925] do_read_cache_folio+0x180/0x298
[ 20.965270] read_cache_page+0x24/0x90
[ 20.965273] __arm64_sys_swapon+0x2e0/0x1208
[ 20.965277] invoke_syscall+0x78/0x108
[ 20.965282] el0_svc_common.constprop.0+0x48/0xf0
[ 20.981702] do_el0_svc+0x24/0x38
[ 20.993773] el0t_64_sync_handler+0x100/0x130
[ 20.993776] el0t_64_sync+0x190/0x198
[ 20.993779] ---[ end trace 0000000000000000 ]---
[ 20.999972] Adding 999420k swap on
/dev/mapper/eng07sys--r113--vg-swap_1. Priority:-2 extents:1
across:999420k SS
This is due to
folio_alloc_buffers() setting GFP_NOFAIL:
struct buffer_head *folio_alloc_buffers(struct folio *folio, unsigned long
size,
bool retry)
{
struct buffer_head *bh, *head;
gfp_t gfp = GFP_NOFS | __GFP_ACCOUNT;
long offset;
struct mem_cgroup *memcg, *old_memcg;
if (retry)
gfp |= __GFP_NOFAIL;
Then rmqueue() checks for order > 1 and GFP_NOFAIL
static inline
struct page *rmqueue(struct zone *preferred_zone,
struct zone *zone, unsigned int order,
gfp_t gfp_flags, unsigned int alloc_flags,
int migratetype)
{
struct page *page;
/*
* We most definitely don't want callers attempting to
* allocate greater than order-1 page units with __GFP_NOFAIL.
*/
WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1));
