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BUG: KCSAN: data-race in blk_mq_get_request / blk_mq_get_request

write to 0xffff88812b1fd148 of 8 bytes by task 14223 on cpu 0:
 blk_mq_get_request+0x91a/0xba0 block/blk-mq.c:396
 blk_mq_make_request+0x2d7/0xf60 block/blk-mq.c:2001
 generic_make_request block/blk-core.c:1075 [inline]
 generic_make_request+0x196/0x700 block/blk-core.c:1017
 submit_bio+0x8f/0x3a0 block/blk-core.c:1200
 submit_bh_wbc+0x40d/0x460 fs/buffer.c:3063
 submit_bh fs/buffer.c:3069 [inline]
 write_dirty_buffer fs/buffer.c:3137 [inline]
 write_dirty_buffer+0x7d/0xf0 fs/buffer.c:3128
 fat_sync_bhs+0x58/0x13e fs/fat/misc.c:357
 fat_ent_write+0xd0/0xf0 fs/fat/fatent.c:417
 fat_chain_add+0x356/0x410 fs/fat/misc.c:130
 fat_add_cluster+0x91/0xd0 fs/fat/inode.c:113
 __fat_get_block fs/fat/inode.c:155 [inline]
 fat_get_block+0x3c6/0x4f0 fs/fat/inode.c:190
 __block_write_begin_int+0x306/0xf80 fs/buffer.c:2002
 __block_write_begin fs/buffer.c:2052 [inline]
 block_write_begin+0x76/0x200 fs/buffer.c:2111
 cont_write_begin+0x3bd/0x660 fs/buffer.c:2460
 fat_write_begin+0x69/0xc0 fs/fat/inode.c:236
 pagecache_write_begin+0x67/0x90 mm/filemap.c:3121
 cont_expand_zero fs/buffer.c:2387 [inline]
 cont_write_begin+0x176/0x660 fs/buffer.c:2450
 fat_write_begin+0x69/0xc0 fs/fat/inode.c:236
 pagecache_write_begin+0x67/0x90 mm/filemap.c:3121
 generic_cont_expand_simple+0xae/0x120 fs/buffer.c:2351
 fat_cont_expand+0x44/0x190 fs/fat/file.c:222
 fat_fallocate+0x195/0x1d0 fs/fat/file.c:300
 vfs_fallocate+0x3b1/0x640 fs/open.c:309
 ksys_fallocate+0x5b/0xa0 fs/open.c:332
 __do_sys_fallocate fs/open.c:340 [inline]
 __se_sys_fallocate fs/open.c:338 [inline]
 __x64_sys_fallocate+0x59/0x70 fs/open.c:338
 do_syscall_64+0xc7/0x3b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88812b1fd148 of 8 bytes by task 14228 on cpu 1:
 blk_mq_get_request+0x907/0xba0 block/blk-mq.c:396
 blk_mq_make_request+0x2d7/0xf60 block/blk-mq.c:2001
 generic_make_request block/blk-core.c:1075 [inline]
 generic_make_request+0x196/0x700 block/blk-core.c:1017
 submit_bio+0x8f/0x3a0 block/blk-core.c:1200
 submit_bh_wbc+0x40d/0x460 fs/buffer.c:3063
 submit_bh fs/buffer.c:3069 [inline]
 write_dirty_buffer fs/buffer.c:3137 [inline]
 write_dirty_buffer+0x7d/0xf0 fs/buffer.c:3128
 fat_sync_bhs+0x58/0x13e fs/fat/misc.c:357
 fat_alloc_clusters+0xa87/0xbf0 fs/fat/fatent.c:539
 fat_add_cluster+0x3b/0xd0 fs/fat/inode.c:108
 __fat_get_block fs/fat/inode.c:155 [inline]
 fat_get_block+0x3c6/0x4f0 fs/fat/inode.c:190
 __block_write_begin_int+0x306/0xf80 fs/buffer.c:2002
 __block_write_begin fs/buffer.c:2052 [inline]
 block_write_begin+0x76/0x200 fs/buffer.c:2111
 cont_write_begin+0x3bd/0x660 fs/buffer.c:2460
 fat_write_begin+0x69/0xc0 fs/fat/inode.c:236
 generic_perform_write+0x13a/0x320 mm/filemap.c:3302
 __generic_file_write_iter+0x240/0x370 mm/filemap.c:3431
 generic_file_write_iter+0x294/0x38e mm/filemap.c:3463
 call_write_iter include/linux/fs.h:1907 [inline]
 new_sync_write+0x303/0x400 fs/read_write.c:484
 __vfs_write+0x9e/0xb0 fs/read_write.c:497
 vfs_write fs/read_write.c:559 [inline]
 vfs_write+0x189/0x380 fs/read_write.c:543
 ksys_write+0xc5/0x1a0 fs/read_write.c:612
 __do_sys_write fs/read_write.c:624 [inline]
 __se_sys_write fs/read_write.c:621 [inline]
 __x64_sys_write+0x49/0x60 fs/read_write.c:621
 do_syscall_64+0xc7/0x3b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 14228 Comm: syz-executor.4 Not tainted 5.7.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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