[PATCH v4 2/2] mm, thp: bail out early in collapse_file for writeback page
From: Rongwei Wang
Date: Sun Oct 10 2021 - 22:25:21 EST
Currently collapse_file does not explicitly check PG_writeback, instead,
page_has_private and try_to_release_page are used to filter writeback
pages. This does not work for xfs with blocksize equal to or larger
than pagesize, because in such case xfs has no page->private.
This makes collapse_file bail out early for writeback page. Otherwise,
xfs end_page_writeback will panic as follows.
page:fffffe00201bcc80 refcount:0 mapcount:0 mapping:ffff0003f88c86a8 index:0x0 pfn:0x84ef32
aops:xfs_address_space_operations [xfs] ino:30000b7 dentry name:"libtest.so"
flags: 0x57fffe0000008027(locked|referenced|uptodate|active|writeback)
raw: 57fffe0000008027 ffff80001b48bc28 ffff80001b48bc28 ffff0003f88c86a8
raw: 0000000000000000 0000000000000000 00000000ffffffff ffff0000c3e9a000
page dumped because: VM_BUG_ON_PAGE(((unsigned int) page_ref_count(page) + 127u <= 127u))
page->mem_cgroup:ffff0000c3e9a000
------------[ cut here ]------------
kernel BUG at include/linux/mm.h:1212!
Internal error: Oops - BUG: 0 [#1] SMP
Modules linked in:
BUG: Bad page state in process khugepaged pfn:84ef32
xfs(E)
page:fffffe00201bcc80 refcount:0 mapcount:0 mapping:0 index:0x0 pfn:0x84ef32
libcrc32c(E) rfkill(E) aes_ce_blk(E) crypto_simd(E) ...
CPU: 25 PID: 0 Comm: swapper/25 Kdump: loaded Tainted: ...
pstate: 60400005 (nZCv daif +PAN -UAO -TCO BTYPE=--)
pc : end_page_writeback+0x1c0/0x214
lr : end_page_writeback+0x1c0/0x214
sp : ffff800011ce3cc0
x29: ffff800011ce3cc0 x28: 0000000000000000
x27: ffff000c04608040 x26: 0000000000000000
x25: ffff000c04608040 x24: 0000000000001000
x23: ffff0003f88c8530 x22: 0000000000001000
x21: ffff0003f88c8530 x20: 0000000000000000
x19: fffffe00201bcc80 x18: 0000000000000030
x17: 0000000000000000 x16: 0000000000000000
x15: ffff000c018f9760 x14: ffffffffffffffff
x13: ffff8000119d72b0 x12: ffff8000119d6ee3
x11: ffff8000117b69b8 x10: 00000000ffff8000
x9 : ffff800010617534 x8 : 0000000000000000
x7 : ffff8000114f69b8 x6 : 000000000000000f
x5 : 0000000000000000 x4 : 0000000000000000
x3 : 0000000000000400 x2 : 0000000000000000
x1 : 0000000000000000 x0 : 0000000000000000
Call trace:
end_page_writeback+0x1c0/0x214
iomap_finish_page_writeback+0x13c/0x204
iomap_finish_ioend+0xe8/0x19c
iomap_writepage_end_bio+0x38/0x50
bio_endio+0x168/0x1ec
blk_update_request+0x278/0x3f0
blk_mq_end_request+0x34/0x15c
virtblk_request_done+0x38/0x74 [virtio_blk]
blk_done_softirq+0xc4/0x110
__do_softirq+0x128/0x38c
__irq_exit_rcu+0x118/0x150
irq_exit+0x1c/0x30
__handle_domain_irq+0x8c/0xf0
gic_handle_irq+0x84/0x108
el1_irq+0xcc/0x180
arch_cpu_idle+0x18/0x40
default_idle_call+0x4c/0x1a0
cpuidle_idle_call+0x168/0x1e0
do_idle+0xb4/0x104
cpu_startup_entry+0x30/0x9c
secondary_start_kernel+0x104/0x180
Code: d4210000 b0006161 910c8021 94013f4d (d4210000)
---[ end trace 4a88c6a074082f8c ]---
Kernel panic - not syncing: Oops - BUG: Fatal exception in interrupt
Fixes: eb6ecbed0aa2 ("mm, thp: relax the VM_DENYWRITE constraint on file-backed THPs")
Suggested-by: Yang Shi <shy828301@xxxxxxxxx>
Signed-off-by: Xu Yu <xuyu@xxxxxxxxxxxxxxxxx>
Signed-off-by: Rongwei Wang <rongwei.wang@xxxxxxxxxxxxxxxxx>
Reviewed-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Reviewed-by: Yang Shi <shy828301@xxxxxxxxx>
---
mm/khugepaged.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 045cc579f724..48de4e1b0783 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1763,6 +1763,10 @@ static void collapse_file(struct mm_struct *mm,
filemap_flush(mapping);
result = SCAN_FAIL;
goto xa_unlocked;
+ } else if (PageWriteback(page)) {
+ xas_unlock_irq(&xas);
+ result = SCAN_FAIL;
+ goto xa_unlocked;
} else if (trylock_page(page)) {
get_page(page);
xas_unlock_irq(&xas);
@@ -1798,7 +1802,8 @@ static void collapse_file(struct mm_struct *mm,
goto out_unlock;
}
- if (!is_shmem && PageDirty(page)) {
+ if (!is_shmem && (PageDirty(page) ||
+ PageWriteback(page))) {
/*
* khugepaged only works on read-only fd, so this
* page is dirty because it hasn't been flushed
--
2.27.0