The patch titled
Subject: mm/page_io: mark various intentional data races
has been added to the -mm tree. Its filename is
mm-page_io-mark-various-intentional-data-races.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-page_io-mark-various-intentional-data-races.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-page_io-mark-various-intentional-data-races.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Qian Cai <cai@xxxxxx>
Subject: mm/page_io: mark various intentional data races
struct swap_info_struct si.flags could be accessed concurrently as noticed
by KCSAN,
BUG: KCSAN: data-race in scan_swap_map_slots / swap_readpage
write to 0xffff9c77b80ac400 of 8 bytes by task 91325 on cpu 16:
scan_swap_map_slots+0x6fe/0xb50
scan_swap_map_slots at mm/swapfile.c:887
get_swap_pages+0x39d/0x5c0
get_swap_page+0x377/0x524
add_to_swap+0xe4/0x1c0
shrink_page_list+0x1740/0x2820
shrink_inactive_list+0x316/0x8b0
shrink_lruvec+0x8dc/0x1380
shrink_node+0x317/0xd80
do_try_to_free_pages+0x1f7/0xa10
try_to_free_pages+0x26c/0x5e0
__alloc_pages_slowpath+0x458/0x1290
__alloc_pages_nodemask+0x3bb/0x450
alloc_pages_vma+0x8a/0x2c0
do_anonymous_page+0x170/0x700
__handle_mm_fault+0xc9f/0xd00
handle_mm_fault+0xfc/0x2f0
do_page_fault+0x263/0x6f9
page_fault+0x34/0x40
read to 0xffff9c77b80ac400 of 8 bytes by task 5422 on cpu 7:
swap_readpage+0x204/0x6a0
swap_readpage at mm/page_io.c:380
read_swap_cache_async+0xa2/0xb0
swapin_readahead+0x6a0/0x890
do_swap_page+0x465/0xeb0
__handle_mm_fault+0xc7a/0xd00
handle_mm_fault+0xfc/0x2f0
do_page_fault+0x263/0x6f9
page_fault+0x34/0x40
Reported by Kernel Concurrency Sanitizer on:
CPU: 7 PID: 5422 Comm: gmain Tainted: G W O L 5.5.0-next-20200204+ #6
Hardware name: HPE ProLiant DL385 Gen10/ProLiant DL385 Gen10, BIOS A40 07/10/2019
Other reads,
read to 0xffff91ea33eac400 of 8 bytes by task 11276 on cpu 120:
__swap_writepage+0x140/0xc20
__swap_writepage at mm/page_io.c:289
read to 0xffff91ea33eac400 of 8 bytes by task 11264 on cpu 16:
swap_set_page_dirty+0x44/0x1f4
swap_set_page_dirty at mm/page_io.c:442
The write is under &si->lock, but the reads are done as lockless. Since
the reads only check for a specific bit in the flag, it is harmless even
if load tearing happens. Thus, just mark them as intentional data races
using the data_race() macro.
Link: http://lkml.kernel.org/r/20200207003601.1526-1-cai@xxxxxx
Signed-off-by: Qian Cai <cai@xxxxxx>
Cc: Marco Elver <elver@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_io.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
--- a/mm/page_io.c~mm-page_io-mark-various-intentional-data-races
+++ a/mm/page_io.c
@@ -286,7 +286,7 @@ int __swap_writepage(struct page *page,
struct swap_info_struct *sis = page_swap_info(page);
VM_BUG_ON_PAGE(!PageSwapCache(page), page);
- if (sis->flags & SWP_FS) {
+ if (data_race(sis->flags & SWP_FS)) {
struct kiocb kiocb;
struct file *swap_file = sis->swap_file;
struct address_space *mapping = swap_file->f_mapping;
@@ -377,7 +377,7 @@ int swap_readpage(struct page *page, boo
goto out;
}
- if (sis->flags & SWP_FS) {
+ if (data_race(sis->flags & SWP_FS)) {
struct file *swap_file = sis->swap_file;
struct address_space *mapping = swap_file->f_mapping;
@@ -439,7 +439,7 @@ int swap_set_page_dirty(struct page *pag
{
struct swap_info_struct *sis = page_swap_info(page);
- if (sis->flags & SWP_FS) {
+ if (data_race(sis->flags & SWP_FS)) {
struct address_space *mapping = sis->swap_file->f_mapping;
VM_BUG_ON_PAGE(!PageSwapCache(page), page);
_
Patches currently in -mm which might be from cai@xxxxxx are
mm-swapfile-fix-and-annotate-various-data-races.patch
mm-list_lru-fix-a-data-race-in-list_lru_count_one.patch
mm-frontswap-mark-various-intentional-data-races.patch
mm-page_io-mark-various-intentional-data-races.patch
mm-swap_state-mark-various-intentional-data-races.patch
