syzbot

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BUG: KCSAN: data-race in atime_needs_update / touch_atime

read to 0xffff888104416710 of 8 bytes by task 49 on cpu 0:
 atime_needs_update+0x268/0x3f0
 touch_atime+0x4a/0x350 fs/inode.c:1975
 file_accessed include/linux/fs.h:2459 [inline]
 shmem_file_read_iter+0x4b3/0x550 mm/shmem.c:2900
 do_iter_readv_writev+0x339/0x3e0
 vfs_iter_read+0x172/0x3a0 fs/read_write.c:830
 lo_read_simple drivers/block/loop.c:286 [inline]
 do_req_filebacked drivers/block/loop.c:496 [inline]
 loop_handle_cmd drivers/block/loop.c:1907 [inline]
 loop_process_work+0x7bc/0x1110 drivers/block/loop.c:1942
 loop_workfn+0x31/0x40 drivers/block/loop.c:1966
 process_one_work kernel/workqueue.c:3254 [inline]
 process_scheduled_works+0x465/0x990 kernel/workqueue.c:3335
 worker_thread+0x526/0x730 kernel/workqueue.c:3416
 kthread+0x1d1/0x210 kernel/kthread.c:388
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

write to 0xffff888104416710 of 8 bytes by task 10 on cpu 1:
 inode_set_atime_to_ts include/linux/fs.h:1566 [inline]
 inode_update_timestamps fs/inode.c:1878 [inline]
 generic_update_time fs/inode.c:1900 [inline]
 inode_update_time fs/inode.c:1920 [inline]
 touch_atime+0x1f3/0x350 fs/inode.c:1992
 file_accessed include/linux/fs.h:2459 [inline]
 shmem_file_read_iter+0x4b3/0x550 mm/shmem.c:2900
 do_iter_readv_writev+0x339/0x3e0
 vfs_iter_read+0x172/0x3a0 fs/read_write.c:830
 lo_read_simple drivers/block/loop.c:286 [inline]
 do_req_filebacked drivers/block/loop.c:496 [inline]
 loop_handle_cmd drivers/block/loop.c:1907 [inline]
 loop_process_work+0x7bc/0x1110 drivers/block/loop.c:1942
 loop_rootcg_workfn+0x22/0x30 drivers/block/loop.c:1973
 process_one_work kernel/workqueue.c:3254 [inline]
 process_scheduled_works+0x465/0x990 kernel/workqueue.c:3335
 worker_thread+0x526/0x730 kernel/workqueue.c:3416
 kthread+0x1d1/0x210 kernel/kthread.c:388
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

value changed: 0x000000002f189046 -> 0x000000002fb126c6

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 10 Comm: kworker/u8:0 Not tainted 6.9.0-rc5-syzkaller-00036-g9d1ddab261f3 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Workqueue: loop3 loop_rootcg_workfn
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