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BUG: KCSAN: data-race in relay_switch_subbuf / relay_switch_subbuf

write to 0xffff888117b82438 of 8 bytes by task 16867 on cpu 0:
 relay_switch_subbuf+0x39e/0x3b0 kernel/relay.c:708
 relay_reserve include/linux/relay.h:248 [inline]
 __blk_add_trace+0x653/0x710 kernel/trace/blktrace.c:276
 blk_add_trace_plug+0x4c/0x70 kernel/trace/blktrace.c:937
 __do_trace_block_plug include/trace/events/block.h:430 [inline]
 trace_block_plug include/trace/events/block.h:430 [inline]
 blk_add_rq_to_plug+0x31b/0x3d0 block/blk-mq.c:1380
 blk_mq_submit_bio+0xa3c/0xf30 block/blk-mq.c:3157
 __submit_bio+0xf2/0x4f0 block/blk-core.c:628
 __submit_bio_noacct_mq block/blk-core.c:715 [inline]
 submit_bio_noacct_nocheck+0x295/0x6e0 block/blk-core.c:744
 submit_bio_noacct+0x6e1/0x930 block/blk-core.c:867
 submit_bio+0x218/0x230 block/blk-core.c:909
 submit_bh_wbc+0x2ed/0x330 fs/buffer.c:2814
 submit_bh fs/buffer.c:2819 [inline]
 write_dirty_buffer+0xf4/0x120 fs/buffer.c:2832
 fat_sync_bhs+0x4b/0x140 fs/fat/misc.c:367
 fat_alloc_clusters+0x941/0xa80 fs/fat/fatent.c:541
 fat_add_cluster fs/fat/inode.c:107 [inline]
 __fat_get_block fs/fat/inode.c:154 [inline]
 fat_get_block+0x25c/0x5e0 fs/fat/inode.c:189
 __block_write_begin_int+0x417/0xfa0 fs/buffer.c:2116
 block_write_begin fs/buffer.c:2226 [inline]
 cont_write_begin+0x546/0x860 fs/buffer.c:2577
 fat_write_begin+0x51/0xe0 fs/fat/inode.c:228
 generic_perform_write+0x1a8/0x4a0 mm/filemap.c:4189
 __generic_file_write_iter+0xa1/0x120 mm/filemap.c:4290
 generic_file_write_iter+0x8f/0x310 mm/filemap.c:4316
 new_sync_write fs/read_write.c:586 [inline]
 vfs_write+0x77b/0x920 fs/read_write.c:679
 ksys_pwrite64 fs/read_write.c:786 [inline]
 __do_sys_pwrite64 fs/read_write.c:794 [inline]
 __se_sys_pwrite64 fs/read_write.c:791 [inline]
 __x64_sys_pwrite64+0xf6/0x150 fs/read_write.c:791
 x64_sys_call+0xab0/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:19
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

write to 0xffff888117b82438 of 8 bytes by task 16870 on cpu 1:
 relay_switch_subbuf+0x39e/0x3b0 kernel/relay.c:708
 relay_reserve include/linux/relay.h:248 [inline]
 __blk_add_trace+0x653/0x710 kernel/trace/blktrace.c:276
 blk_add_trace_unplug+0x81/0xc0 kernel/trace/blktrace.c:957
 __do_trace_block_unplug include/trace/events/block.h:475 [inline]
 trace_block_unplug include/trace/events/block.h:475 [inline]
 blk_mq_flush_plug_list+0xe9c/0xef0 block/blk-mq.c:2895
 __blk_flush_plug+0x216/0x290 block/blk-core.c:1213
 blk_finish_plug block/blk-core.c:1240 [inline]
 __submit_bio+0x301/0x4f0 block/blk-core.c:642
 __submit_bio_noacct_mq block/blk-core.c:715 [inline]
 submit_bio_noacct_nocheck+0x295/0x6e0 block/blk-core.c:744
 submit_bio_noacct+0x6e1/0x930 block/blk-core.c:867
 submit_bio+0x218/0x230 block/blk-core.c:909
 submit_bh_wbc+0x2ed/0x330 fs/buffer.c:2814
 submit_bh fs/buffer.c:2819 [inline]
 __sync_dirty_buffer+0x171/0x250 fs/buffer.c:2857
 sync_dirty_buffer+0x1a/0x20 fs/buffer.c:2870
 fat_mirror_bhs+0x279/0x330 fs/fat/fatent.c:400
 fat_alloc_clusters+0x994/0xa80 fs/fat/fatent.c:543
 fat_add_cluster fs/fat/inode.c:107 [inline]
 __fat_get_block fs/fat/inode.c:154 [inline]
 fat_get_block+0x25c/0x5e0 fs/fat/inode.c:189
 __block_write_begin_int+0x417/0xfa0 fs/buffer.c:2116
 block_write_begin fs/buffer.c:2226 [inline]
 cont_write_begin+0x546/0x860 fs/buffer.c:2577
 fat_write_begin+0x51/0xe0 fs/fat/inode.c:228
 cont_expand_zero fs/buffer.c:2504 [inline]
 cont_write_begin+0x18b/0x860 fs/buffer.c:2567
 fat_write_begin+0x51/0xe0 fs/fat/inode.c:228
 generic_cont_expand_simple+0xaa/0x150 fs/buffer.c:2468
 fat_cont_expand+0x3a/0x160 fs/fat/file.c:223
 fat_fallocate+0x17c/0x1d0 fs/fat/file.c:301
 vfs_fallocate+0x368/0x3b0 fs/open.c:338
 ksys_fallocate fs/open.c:362 [inline]
 __do_sys_fallocate fs/open.c:367 [inline]
 __se_sys_fallocate fs/open.c:365 [inline]
 __x64_sys_fallocate+0x78/0xc0 fs/open.c:365
 x64_sys_call+0x43c/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:286
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000000030 -> 0x0000000000000038

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 16870 Comm: syz.3.5093 Not tainted 6.14.0-rc2-syzkaller-00281-g496659003dac #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
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