syzbot

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BUG: KCSAN: data-race in dentry_lru_isolate / link_path_walk

write to 0xffff888125a60240 of 4 bytes by task 18466 on cpu 1:
 d_lru_isolate fs/dcache.c:442 [inline]
 dentry_lru_isolate+0x9f/0x200 fs/dcache.c:1166
 __list_lru_walk_one+0xfb/0x320 mm/list_lru.c:222
 list_lru_walk_one+0x75/0x90 mm/list_lru.c:266
 list_lru_shrink_walk include/linux/list_lru.h:195 [inline]
 prune_dcache_sb+0x67/0xa0 fs/dcache.c:1220
 super_cache_scan+0x23b/0x2d0 fs/super.c:105
 do_shrink_slab+0x286/0x5c0 mm/vmscan.c:513
 shrink_slab+0xea/0x1c0 mm/vmscan.c:674
 shrink_node_memcgs+0x270/0x410 mm/vmscan.c:2653
 shrink_node+0x9ed/0x1230 mm/vmscan.c:2768
 shrink_zones+0x2af/0x490 mm/vmscan.c:2971
 do_try_to_free_pages+0x193/0x6e0 mm/vmscan.c:3026
 try_to_free_pages+0x38e/0x8b0 mm/vmscan.c:3265
 __perform_reclaim mm/page_alloc.c:4260 [inline]
 __alloc_pages_direct_reclaim mm/page_alloc.c:4281 [inline]
 __alloc_pages_slowpath+0x55f/0x9e0 mm/page_alloc.c:4685
 __alloc_pages_nodemask+0x266/0x380 mm/page_alloc.c:4901
 alloc_pages_vma+0x3e6/0x890 mm/mempolicy.c:2238
 shmem_alloc_page mm/shmem.c:1565 [inline]
 shmem_alloc_and_acct_page+0x2ba/0x650 mm/shmem.c:1590
 shmem_getpage_gfp+0x669/0x19c0 mm/shmem.c:1886
 shmem_getpage mm/shmem.c:155 [inline]
 shmem_write_begin+0x83/0x100 mm/shmem.c:2523
 generic_perform_write+0x196/0x390 mm/filemap.c:3501
 __generic_file_write_iter+0x154/0x330 mm/filemap.c:3630
 generic_file_write_iter+0x2f3/0x3e0 mm/filemap.c:3662
 call_write_iter include/linux/fs.h:1882 [inline]
 new_sync_write fs/read_write.c:503 [inline]
 vfs_write+0x665/0x6f0 fs/read_write.c:578
 ksys_write+0xce/0x180 fs/read_write.c:631
 __do_sys_write fs/read_write.c:643 [inline]
 __se_sys_write fs/read_write.c:640 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:640
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888125a60240 of 4 bytes by task 5073 on cpu 0:
 link_path_walk+0x334/0x730 fs/namei.c:2145
 path_lookupat+0x7b/0x560 fs/namei.c:2332
 filename_lookup+0xf2/0x380 fs/namei.c:2366
 user_path_at_empty+0x3b/0x50 fs/namei.c:2646
 user_path_at include/linux/namei.h:59 [inline]
 vfs_statx+0xb8/0x2b0 fs/stat.c:202
 vfs_lstat include/linux/fs.h:3178 [inline]
 __do_sys_newlstat fs/stat.c:374 [inline]
 __se_sys_newlstat+0x46/0x250 fs/stat.c:368
 __x64_sys_newlstat+0x2d/0x40 fs/stat.c:368
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 5073 Comm: systemd-udevd Not tainted 5.9.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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