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BUG: KCSAN: data-race in relay_switch_subbuf / relay_switch_subbuf

write to 0xffff88814c39f438 of 8 bytes by task 10814 on cpu 1:
 relay_switch_subbuf+0x399/0x3a0 kernel/relay.c:708
 relay_reserve include/linux/relay.h:248 [inline]
 __blk_add_trace+0x665/0x720 kernel/trace/blktrace.c:276
 blk_add_trace_plug+0x4c/0x60 kernel/trace/blktrace.c:950
 trace_block_plug include/trace/events/block.h:407 [inline]
 blk_add_rq_to_plug+0x2b4/0x3e0 block/blk-mq.c:1295
 blk_mq_submit_bio+0x692/0xd70 block/blk-mq.c:3012
 __submit_bio+0x11c/0x350 block/blk-core.c:599
 __submit_bio_noacct_mq block/blk-core.c:678 [inline]
 submit_bio_noacct_nocheck+0x4ad/0x5e0 block/blk-core.c:707
 submit_bio_noacct+0x700/0x8a0 block/blk-core.c:801
 submit_bio+0xb7/0xc0 block/blk-core.c:834
 ext4_io_submit fs/ext4/page-io.c:378 [inline]
 io_submit_add_bh fs/ext4/page-io.c:419 [inline]
 ext4_bio_write_folio+0x6c0/0x9a0 fs/ext4/page-io.c:563
 mpage_submit_folio fs/ext4/inode.c:1865 [inline]
 mpage_map_and_submit_buffers fs/ext4/inode.c:2111 [inline]
 mpage_map_and_submit_extent fs/ext4/inode.c:2250 [inline]
 ext4_do_writepages+0x139f/0x2100 fs/ext4/inode.c:2675
 ext4_writepages+0x15e/0x2e0 fs/ext4/inode.c:2764
 do_writepages+0x1c2/0x340 mm/page-writeback.c:2553
 filemap_fdatawrite_wbc+0xdb/0xf0 mm/filemap.c:390
 __filemap_fdatawrite_range mm/filemap.c:423 [inline]
 __filemap_fdatawrite mm/filemap.c:429 [inline]
 filemap_flush+0x95/0xc0 mm/filemap.c:456
 ext4_alloc_da_blocks+0x50/0x130 fs/ext4/inode.c:3067
 ext4_release_file+0x5f/0x1c0 fs/ext4/file.c:169
 __fput+0x2fd/0x5f0 fs/file_table.c:384
 __fput_sync+0x44/0x50 fs/file_table.c:465
 __do_sys_close fs/open.c:1572 [inline]
 __se_sys_close+0xfa/0x1a0 fs/open.c:1557
 __x64_sys_close+0x1f/0x30 fs/open.c:1557
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

write to 0xffff88814c39f438 of 8 bytes by task 10802 on cpu 0:
 relay_switch_subbuf+0x399/0x3a0 kernel/relay.c:708
 relay_reserve include/linux/relay.h:248 [inline]
 __blk_add_trace+0x665/0x720 kernel/trace/blktrace.c:276
 blk_add_trace_plug+0x4c/0x60 kernel/trace/blktrace.c:950
 trace_block_plug include/trace/events/block.h:407 [inline]
 blk_add_rq_to_plug+0x2b4/0x3e0 block/blk-mq.c:1295
 blk_mq_submit_bio+0x692/0xd70 block/blk-mq.c:3012
 __submit_bio+0x11c/0x350 block/blk-core.c:599
 __submit_bio_noacct_mq block/blk-core.c:678 [inline]
 submit_bio_noacct_nocheck+0x4ad/0x5e0 block/blk-core.c:707
 submit_bio_noacct+0x700/0x8a0 block/blk-core.c:801
 submit_bio+0xb7/0xc0 block/blk-core.c:834
 ext4_io_submit fs/ext4/page-io.c:378 [inline]
 io_submit_add_bh fs/ext4/page-io.c:419 [inline]
 ext4_bio_write_folio+0x6c0/0x9a0 fs/ext4/page-io.c:563
 mpage_submit_folio fs/ext4/inode.c:1865 [inline]
 mpage_map_and_submit_buffers fs/ext4/inode.c:2111 [inline]
 mpage_map_and_submit_extent fs/ext4/inode.c:2250 [inline]
 ext4_do_writepages+0x139f/0x2100 fs/ext4/inode.c:2675
 ext4_writepages+0x15e/0x2e0 fs/ext4/inode.c:2764
 do_writepages+0x1c2/0x340 mm/page-writeback.c:2553
 filemap_fdatawrite_wbc+0xdb/0xf0 mm/filemap.c:390
 __filemap_fdatawrite_range mm/filemap.c:423 [inline]
 __filemap_fdatawrite mm/filemap.c:429 [inline]
 filemap_flush+0x95/0xc0 mm/filemap.c:456
 ext4_alloc_da_blocks+0x50/0x130 fs/ext4/inode.c:3067
 ext4_release_file+0x5f/0x1c0 fs/ext4/file.c:169
 __fput+0x2fd/0x5f0 fs/file_table.c:384
 __fput_sync+0x44/0x50 fs/file_table.c:465
 __do_sys_close fs/open.c:1572 [inline]
 __se_sys_close+0xfa/0x1a0 fs/open.c:1557
 __x64_sys_close+0x1f/0x30 fs/open.c:1557
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x0000000000000038 -> 0x0000000000000030

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 10802 Comm: syz-executor.1 Tainted: G        W          6.6.0-rc4-syzkaller-00037-g3006adf3be79 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/06/2023
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