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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.

[cai@lca.pw: add a missing annotation]
  Link: http://lkml.kernel.org/r/1581612585-5812-1-git-send-email-cai@lca.pw

Signed-off-by: Qian Cai <cai@lca.pw>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Marco Elver <elver@google.com>
Link: http://lkml.kernel.org/r/20200207003601.1526-1-cai@lca.pw
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Qian Cai 2020-08-14 17:31:20 -07:00 committed by Linus Torvalds
parent 96bdd2bcc1
commit 7b37e22675
1 changed files with 4 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
mm/page_io.c
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@ -85,7 +85,7 @@ static void swap_slot_free_notify(struct page *page)
return;
sis = page_swap_info(page);
if (!(sis->flags & SWP_BLKDEV))
if (data_race(!(sis->flags & SWP_BLKDEV)))
return;
/*
@ -302,7 +302,7 @@ int __swap_writepage(struct page *page, struct writeback_control *wbc,
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;
@ -393,7 +393,7 @@ int swap_readpage(struct page *page, bool synchronous)
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;
@ -455,7 +455,7 @@ int swap_set_page_dirty(struct page *page)
{
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);