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BUG: KCSAN: data-race in atime_needs_update / touch_atime

read to 0xffff88814677d360 of 8 bytes by task 6338 on cpu 1:
 timespec64_equal include/linux/time64.h:49 [inline]
 atime_needs_update+0x3f2/0x5b0 fs/inode.c:1992
 touch_atime+0x58/0x4a0 fs/inode.c:2003
 file_accessed include/linux/fs.h:2320 [inline]
 shmem_file_read_iter+0x570/0x5b0 mm/shmem.c:2845
 do_iter_read+0x4ac/0x7c0 fs/read_write.c:795
 vfs_iter_read+0x56/0x70 fs/read_write.c:837
 lo_read_simple drivers/block/loop.c:290 [inline]
 do_req_filebacked drivers/block/loop.c:500 [inline]
 loop_handle_cmd drivers/block/loop.c:1915 [inline]
 loop_process_work+0x98c/0x12e0 drivers/block/loop.c:1950
 loop_rootcg_workfn+0x22/0x30 drivers/block/loop.c:1981
 process_one_work kernel/workqueue.c:2630 [inline]
 process_scheduled_works+0x5b8/0xa30 kernel/workqueue.c:2703
 worker_thread+0x525/0x730 kernel/workqueue.c:2784
 kthread+0x1d7/0x210 kernel/kthread.c:388
 ret_from_fork+0x48/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304

write to 0xffff88814677d360 of 8 bytes by task 32644 on cpu 0:
 inode_update_timestamps fs/inode.c:1907 [inline]
 generic_update_time fs/inode.c:1929 [inline]
 inode_update_time fs/inode.c:1949 [inline]
 touch_atime+0x31f/0x4a0 fs/inode.c:2020
 file_accessed include/linux/fs.h:2320 [inline]
 shmem_file_read_iter+0x570/0x5b0 mm/shmem.c:2845
 do_iter_read+0x4ac/0x7c0 fs/read_write.c:795
 vfs_iter_read+0x56/0x70 fs/read_write.c:837
 lo_read_simple drivers/block/loop.c:290 [inline]
 do_req_filebacked drivers/block/loop.c:500 [inline]
 loop_handle_cmd drivers/block/loop.c:1915 [inline]
 loop_process_work+0x98c/0x12e0 drivers/block/loop.c:1950
 loop_workfn+0x31/0x40 drivers/block/loop.c:1974
 process_one_work kernel/workqueue.c:2630 [inline]
 process_scheduled_works+0x5b8/0xa30 kernel/workqueue.c:2703
 worker_thread+0x525/0x730 kernel/workqueue.c:2784
 kthread+0x1d7/0x210 kernel/kthread.c:388
 ret_from_fork+0x48/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304

value changed: 0x000000001955d0c2 -> 0x0000000019ee6742

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 32644 Comm: kworker/u4:17 Not tainted 6.6.0-rc1-syzkaller-00196-g57d88e8a5974 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/04/2023
Workqueue: loop3 loop_workfn
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