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BUG: KCSAN: data-race in __delete_from_page_cache / shmem_getpage_gfp

write to 0xffff888109e27f50 of 8 bytes by task 5329 on cpu 0:
 page_cache_delete mm/filemap.c:145 [inline]
 __delete_from_page_cache+0x1c1/0x260 mm/filemap.c:230
 delete_from_page_cache+0x85/0x140 mm/filemap.c:265
 truncate_inode_page+0x3e/0x50 mm/truncate.c:219
 shmem_undo_range+0x210/0xe20 mm/shmem.c:927
 shmem_truncate_range mm/shmem.c:1030 [inline]
 shmem_fallocate+0x2a3/0x840 mm/shmem.c:2700
 vfs_fallocate+0x463/0x660 fs/open.c:311
 madvise_remove+0x126/0x1e0 mm/madvise.c:925
 madvise_vma mm/madvise.c:987 [inline]
 do_madvise+0x53c/0x10a0 mm/madvise.c:1201
 __do_sys_madvise mm/madvise.c:1227 [inline]
 __se_sys_madvise mm/madvise.c:1225 [inline]
 __x64_sys_madvise+0x5d/0x70 mm/madvise.c:1225
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888109e27f50 of 8 bytes by task 5306 on cpu 1:
 shmem_recalc_inode mm/shmem.c:367 [inline]
 shmem_getpage_gfp+0xfca/0x13d0 mm/shmem.c:1961
 shmem_fault+0x16d/0x500 mm/shmem.c:2138
 __do_fault mm/memory.c:3857 [inline]
 do_read_fault mm/memory.c:4172 [inline]
 do_fault mm/memory.c:4300 [inline]
 handle_pte_fault mm/memory.c:4558 [inline]
 __handle_mm_fault mm/memory.c:4693 [inline]
 handle_mm_fault+0xe6d/0x1a50 mm/memory.c:4791
 faultin_page mm/gup.c:951 [inline]
 __get_user_pages+0x32b/0xbc0 mm/gup.c:1173
 populate_vma_page_range mm/gup.c:1506 [inline]
 __mm_populate+0x24d/0x380 mm/gup.c:1615
 mm_populate include/linux/mm.h:2623 [inline]
 vm_mmap_pgoff+0x142/0x1d0 mm/util.c:524
 ksys_mmap_pgoff+0xe1/0x380 mm/mmap.c:1635
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x000000000000069d -> 0x0000000000000694

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 5306 Comm: syz-executor.5 Not tainted 5.14.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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