KCSAN: data-race in __add_to_page_cache_locked / nr_blockdev_pages (4)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: fa02fcd9 Merge tag 'media/v5.10-2' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1576a065500000
kernel config: https://syzkaller.appspot.com/x/.config?x=9b9b19d1bde60f8d
dashboard link: https://syzkaller.appspot.com/bug?extid=b1a18041d678e07fa304
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project.git 913f6005669cfb590c99865a90bc51ed0983d09d)
CC: [ak...@linux-foundation.org linux-...@vger.kernel.org linu...@kvack.org]

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b1a180...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __add_to_page_cache_locked / nr_blockdev_pages

read-write to 0xffff88810be983d0 of 8 bytes by task 13808 on cpu 1:
__add_to_page_cache_locked+0x39d/0x7b0 mm/filemap.c:888
add_to_page_cache_lru+0xa0/0x1b0 mm/filemap.c:939
page_cache_ra_unbounded+0x272/0x4c0 mm/readahead.c:222
do_page_cache_ra mm/readahead.c:267 [inline]
force_page_cache_ra+0x226/0x260 mm/readahead.c:298
page_cache_sync_ra+0x194/0x1c0 mm/readahead.c:572
page_cache_sync_readahead include/linux/pagemap.h:839 [inline]
generic_file_buffered_read+0x388/0x23a0 mm/filemap.c:2235
generic_file_read_iter+0x80/0x3d0 mm/filemap.c:2553
blkdev_read_iter+0xb3/0xc0 fs/block_dev.c:1925
call_read_iter include/linux/fs.h:1897 [inline]
new_sync_read fs/read_write.c:415 [inline]
vfs_read+0x552/0x5c0 fs/read_write.c:496
ksys_read+0xce/0x180 fs/read_write.c:634
__do_sys_read fs/read_write.c:644 [inline]
__se_sys_read fs/read_write.c:642 [inline]
__x64_sys_read+0x3e/0x50 fs/read_write.c:642
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88810be983d0 of 8 bytes by task 9172 on cpu 0:
nr_blockdev_pages+0x7c/0xd0 fs/block_dev.c:946
si_meminfo+0x3a/0x60 mm/page_alloc.c:5335
update_defense_level+0x34/0x550 net/netfilter/ipvs/ip_vs_ctl.c:101
defense_work_handler+0x1b/0x80 net/netfilter/ipvs/ip_vs_ctl.c:235
process_one_work+0x3e1/0x950 kernel/workqueue.c:2272
worker_thread+0x635/0xb90 kernel/workqueue.c:2418
kthread+0x1fd/0x220 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 9172 Comm: kworker/0:5 Not tainted 5.10.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events_long defense_work_handler
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.