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BUG: KCSAN: data-race in atime_needs_update / touch_atime

write to 0xffff88811ac4c3d8 of 4 bytes by task 1730 on cpu 0:
 inode_set_atime_to_ts include/linux/fs.h:1624 [inline]
 inode_update_timestamps fs/inode.c:2129 [inline]
 generic_update_time fs/inode.c:2151 [inline]
 inode_update_time fs/inode.c:2171 [inline]
 touch_atime+0x1e8/0x340 fs/inode.c:2243
 file_accessed include/linux/fs.h:2254 [inline]
 shmem_file_read_iter+0x477/0x540 mm/shmem.c:3470
 lo_rw_aio+0x67d/0x730 drivers/block/loop.c:-1
 do_req_filebacked drivers/block/loop.c:-1 [inline]
 loop_handle_cmd drivers/block/loop.c:1947 [inline]
 loop_process_work+0x56c/0xac0 drivers/block/loop.c:1982
 loop_rootcg_workfn+0x22/0x30 drivers/block/loop.c:2013
 process_one_work kernel/workqueue.c:3257 [inline]
 process_scheduled_works+0x4cd/0x9d0 kernel/workqueue.c:3340
 worker_thread+0x581/0x770 kernel/workqueue.c:3421
 kthread+0x488/0x510 kernel/kthread.c:463
 ret_from_fork+0x148/0x280 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

read to 0xffff88811ac4c3d8 of 4 bytes by task 13832 on cpu 1:
 atime_needs_update+0x25f/0x3e0 fs/inode.c:-1
 touch_atime+0x4a/0x340 fs/inode.c:2226
 file_accessed include/linux/fs.h:2254 [inline]
 shmem_file_read_iter+0x477/0x540 mm/shmem.c:3470
 lo_rw_aio+0x67d/0x730 drivers/block/loop.c:-1
 do_req_filebacked drivers/block/loop.c:-1 [inline]
 loop_handle_cmd drivers/block/loop.c:1947 [inline]
 loop_process_work+0x56c/0xac0 drivers/block/loop.c:1982
 loop_workfn+0x31/0x40 drivers/block/loop.c:2006
 process_one_work kernel/workqueue.c:3257 [inline]
 process_scheduled_works+0x4cd/0x9d0 kernel/workqueue.c:3340
 worker_thread+0x581/0x770 kernel/workqueue.c:3421
 kthread+0x488/0x510 kernel/kthread.c:463
 ret_from_fork+0x148/0x280 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

value changed: 0x20218087 -> 0x20b8778b

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 13832 Comm: kworker/u8:17 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: loop8 loop_workfn
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