loop3: detected capacity change from 0 to 8192
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BUG: KCSAN: data-race in relay_switch_subbuf / relay_switch_subbuf

write to 0xffff888117e42238 of 8 bytes by task 7932 on cpu 0:
 relay_switch_subbuf+0x39e/0x3b0 kernel/relay.c:708
 relay_reserve include/linux/relay.h:248 [inline]
 __blk_add_trace+0x66a/0x730 kernel/trace/blktrace.c:276
 blk_add_trace_plug+0x4c/0x70 kernel/trace/blktrace.c:949
 trace_block_plug include/trace/events/block.h:430 [inline]
 blk_add_rq_to_plug+0x31b/0x3d0 block/blk-mq.c:1378
 blk_mq_submit_bio+0x96c/0xe40 block/blk-mq.c:3146
 __submit_bio+0xf2/0x470 block/blk-core.c:629
 __submit_bio_noacct_mq block/blk-core.c:710 [inline]
 submit_bio_noacct_nocheck+0x295/0x6e0 block/blk-core.c:739
 submit_bio_noacct+0x766/0x9a0 block/blk-core.c:868
 submit_bio+0x218/0x230 block/blk-core.c:910
 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:4046
 __generic_file_write_iter+0xa1/0x120 mm/filemap.c:4147
 generic_file_write_iter+0x77/0x1c0 mm/filemap.c:4173
 new_sync_write fs/read_write.c:586 [inline]
 vfs_write+0x77f/0x920 fs/read_write.c:679
 ksys_write+0xe8/0x1b0 fs/read_write.c:731
 __do_sys_write fs/read_write.c:742 [inline]
 __se_sys_write fs/read_write.c:739 [inline]
 __x64_sys_write+0x42/0x50 fs/read_write.c:739
 x64_sys_call+0x287e/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:2
 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 0xffff888117e42238 of 8 bytes by task 7917 on cpu 1:
 relay_switch_subbuf+0x39e/0x3b0 kernel/relay.c:708
 relay_reserve include/linux/relay.h:248 [inline]
 __blk_add_trace+0x66a/0x730 kernel/trace/blktrace.c:276
 blk_add_trace_bio kernel/trace/blktrace.c:902 [inline]
 blk_add_trace_getrq+0x130/0x140 kernel/trace/blktrace.c:939
 trace_block_getrq include/trace/events/block.h:417 [inline]
 blk_mq_submit_bio+0xdd8/0xe40 block/blk-mq.c:3125
 __submit_bio+0xf2/0x470 block/blk-core.c:629
 __submit_bio_noacct_mq block/blk-core.c:710 [inline]
 submit_bio_noacct_nocheck+0x295/0x6e0 block/blk-core.c:739
 submit_bio_noacct+0x766/0x9a0 block/blk-core.c:868
 submit_bio+0x218/0x230 block/blk-core.c:910
 submit_bio_wait+0x87/0xd0 block/bio.c:1391
 blkdev_issue_flush+0x53/0x80 block/blk-flush.c:473
 fat_file_fsync+0xe5/0x100 fs/fat/file.c:199
 vfs_fsync_range+0x116/0x130 fs/sync.c:187
 generic_write_sync include/linux/fs.h:2904 [inline]
 generic_file_write_iter+0x185/0x1c0 mm/filemap.c:4177
 iter_file_splice_write+0x5f1/0x980 fs/splice.c:743
 do_splice_from fs/splice.c:941 [inline]
 direct_splice_actor+0x160/0x2c0 fs/splice.c:1164
 splice_direct_to_actor+0x302/0x670 fs/splice.c:1108
 do_splice_direct_actor fs/splice.c:1207 [inline]
 do_splice_direct+0xd7/0x150 fs/splice.c:1233
 do_sendfile+0x398/0x660 fs/read_write.c:1363
 __do_sys_sendfile64 fs/read_write.c:1424 [inline]
 __se_sys_sendfile64 fs/read_write.c:1410 [inline]
 __x64_sys_sendfile64+0x110/0x150 fs/read_write.c:1410
 x64_sys_call+0xfbd/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:41
 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: 7917 Comm: syz.3.1346 Not tainted 6.13.0-rc6-syzkaller-00051-geea6e4b4dfb8 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
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