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BUG: KCSAN: data-race in __delete_from_page_cache / shmem_getpage_gfp

read-write to 0xffff88810c62ce08 of 8 bytes by task 22504 on cpu 0:
 page_cache_delete mm/filemap.c:154 [inline]
 __delete_from_page_cache+0x26e/0x340 mm/filemap.c:239
 __remove_mapping+0x3e4/0x480 mm/vmscan.c:928
 shrink_page_list+0x17a8/0x2260 mm/vmscan.c:1431
 reclaim_pages+0x40c/0x540 mm/vmscan.c:2154
 madvise_cold_or_pageout_pte_range+0xcaf/0x14a0 mm/madvise.c:473
 walk_pmd_range mm/pagewalk.c:89 [inline]
 walk_pud_range mm/pagewalk.c:160 [inline]
 walk_p4d_range mm/pagewalk.c:193 [inline]
 walk_pgd_range mm/pagewalk.c:229 [inline]
 __walk_page_range+0xa0b/0x1310 mm/pagewalk.c:331
 walk_page_range+0x111/0x2e0 mm/pagewalk.c:427
 madvise_vma mm/madvise.c:520 [inline]
 do_madvise+0x61e/0xdc0 mm/madvise.c:1132
 __do_sys_madvise mm/madvise.c:1158 [inline]
 __se_sys_madvise mm/madvise.c:1156 [inline]
 __x64_sys_madvise+0x5d/0x70 mm/madvise.c:1156
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88810c62ce08 of 8 bytes by task 22498 on cpu 1:
 shmem_recalc_inode mm/shmem.c:367 [inline]
 shmem_getpage_gfp+0xb9a/0x1960 mm/shmem.c:1937
 shmem_fault+0x16c/0x450 mm/shmem.c:2114
 __do_fault mm/memory.c:3625 [inline]
 do_read_fault+0x403/0x760 mm/memory.c:4019
 do_fault mm/memory.c:4147 [inline]
 handle_pte_fault mm/memory.c:4387 [inline]
 __handle_mm_fault mm/memory.c:4522 [inline]
 handle_mm_fault+0xff1/0x17b0 mm/memory.c:4620
 do_user_addr_fault+0x433/0x830 arch/x86/mm/fault.c:1393
 handle_page_fault arch/x86/mm/fault.c:1450 [inline]
 exc_page_fault+0x94/0x2a0 arch/x86/mm/fault.c:1506
 asm_exc_page_fault+0x1e/0x30 arch/x86/include/asm/idtentry.h:580
 __get_user_nocheck_1+0x6/0x10 arch/x86/lib/getuser.S:103
 fault_in_pages_readable include/linux/pagemap.h:747 [inline]
 iov_iter_fault_in_readable+0x155/0x3a0 lib/iov_iter.c:438
 generic_perform_write+0xd2/0x3a0 mm/filemap.c:3398
 ext4_buffered_write_iter+0x2e5/0x3d0 fs/ext4/file.c:270
 ext4_file_write_iter+0x45e/0x1090 fs/ext4/file.c:503
 call_write_iter include/linux/fs.h:1901 [inline]
 new_sync_write fs/read_write.c:518 [inline]
 vfs_write+0x6d4/0x7c0 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+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 22498 Comm: syz-executor.3 Not tainted 5.11.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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