syzbot

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BUG: KCSAN: data-race in dentry_lru_isolate / vfs_readlink

write to 0xffff88810bfb0f00 of 4 bytes by task 18630 on cpu 0:
 d_lru_isolate fs/dcache.c:442 [inline]
 dentry_lru_isolate+0x9f/0x200 fs/dcache.c:1199
 __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:1253
 super_cache_scan+0x23e/0x2e0 fs/super.c:105
 do_shrink_slab+0x28b/0x550 mm/vmscan.c:512
 shrink_slab+0xea/0x1c0 mm/vmscan.c:673
 drop_slab_node mm/vmscan.c:707 [inline]
 drop_slab+0xe5/0x160 mm/vmscan.c:717
 drop_caches_sysctl_handler+0xd0/0x1a0 fs/drop_caches.c:65
 proc_sys_call_handler+0x3dd/0x530 fs/proc/proc_sysctl.c:591
 proc_sys_write+0x1e/0x30 fs/proc/proc_sysctl.c:617
 call_write_iter include/linux/fs.h:1977 [inline]
 new_sync_write fs/read_write.c:518 [inline]
 vfs_write+0x6f9/0x7e0 fs/read_write.c:605
 ksys_write+0xce/0x180 fs/read_write.c:658
 __do_sys_write fs/read_write.c:670 [inline]
 __se_sys_write fs/read_write.c:667 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:667
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88810bfb0f00 of 4 bytes by task 4830 on cpu 1:
 __d_entry_type include/linux/dcache.h:394 [inline]
 d_is_symlink include/linux/dcache.h:424 [inline]
 vfs_readlink+0x1c1/0x260 fs/namei.c:4796
 do_readlinkat+0x170/0x200 fs/stat.c:429
 __do_sys_readlinkat fs/stat.c:444 [inline]
 __se_sys_readlinkat fs/stat.c:441 [inline]
 __x64_sys_readlinkat+0x4f/0x60 fs/stat.c:441
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 4830 Comm: systemd-journal Not tainted 5.12.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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