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BUG: KCSAN: data-race in blk_mq_get_request / blk_mq_get_request

read to 0xffff888129a62d48 of 8 bytes by task 7799 on cpu 1:
 blk_mq_get_request+0x8b6/0xb40 block/blk-mq.c:407
 blk_mq_make_request+0x2d9/0xf40 block/blk-mq.c:1958
 generic_make_request block/blk-core.c:1052 [inline]
 generic_make_request+0x196/0x740 block/blk-core.c:994
 submit_bio+0x92/0x310 block/blk-core.c:1163
 submit_bh_wbc+0x40f/0x460 fs/buffer.c:3095
 submit_bh fs/buffer.c:3101 [inline]
 __sync_dirty_buffer+0xd3/0x200 fs/buffer.c:3187
 sync_dirty_buffer+0x24/0x40 fs/buffer.c:3200
 ext4_write_inode+0x312/0x330 fs/ext4/inode.c:5452
 write_inode fs/fs-writeback.c:1224 [inline]
 __writeback_single_inode+0x6eb/0x8d0 fs/fs-writeback.c:1423
 writeback_single_inode+0x22f/0x2f0 fs/fs-writeback.c:1477
 sync_inode fs/fs-writeback.c:2514 [inline]
 sync_inode_metadata+0x74/0xa0 fs/fs-writeback.c:2534
 __generic_file_fsync+0x122/0x190 fs/libfs.c:1007
 ext4_sync_file+0x48e/0xb00 fs/ext4/fsync.c:120
 vfs_fsync_range+0x82/0x150 fs/sync.c:197

write to 0xffff888129a62d48 of 8 bytes by task 7794 on cpu 0:
 blk_mq_get_request+0x8c9/0xb40 block/blk-mq.c:407
 blk_mq_make_request+0x2d9/0xf40 block/blk-mq.c:1958
 generic_make_request block/blk-core.c:1052 [inline]
 generic_make_request+0x196/0x740 block/blk-core.c:994
 submit_bio+0x92/0x310 block/blk-core.c:1163
 ext4_mpage_readpages+0xb12/0x1270 fs/ext4/readpage.c:293
 ext4_readpages+0x92/0xc0 fs/ext4/inode.c:3388
 read_pages+0xa2/0x2d0 mm/readahead.c:126
 __do_page_cache_readahead+0x353/0x390 mm/readahead.c:212
 ra_submit mm/internal.h:62 [inline]
 ondemand_readahead+0x35d/0x710 mm/readahead.c:492
 page_cache_sync_readahead+0x1ad/0x1e0 mm/readahead.c:527
 generic_file_buffered_read mm/filemap.c:2071 [inline]
 generic_file_read_iter+0xeb6/0x1440 mm/filemap.c:2344
 ext4_file_read_iter fs/ext4/file.c:77 [inline]
 ext4_file_read_iter+0xfa/0x240 fs/ext4/file.c:65
 call_read_iter include/linux/fs.h:1864 [inline]
 generic_file_splice_read+0x35c/0x500 fs/splice.c:307

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 7794 Comm: syz-executor.5 Not tainted 5.3.0+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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