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BUG: KCSAN: data-race in __delete_from_page_cache / shmem_getpage_gfp

write to 0xffff888105301ad0 of 8 bytes by task 16864 on cpu 0:
 page_cache_delete mm/filemap.c:147 [inline]
 __delete_from_page_cache+0x1cd/0x270 mm/filemap.c:232
 delete_from_page_cache+0x82/0x160 mm/filemap.c:266
 truncate_inode_page+0x3e/0x50 mm/truncate.c:219
 shmem_undo_range+0x260/0xe70 mm/shmem.c:955
 shmem_truncate_range mm/shmem.c:1058 [inline]
 shmem_setattr+0x375/0x450 mm/shmem.c:1117
 notify_change+0x8a3/0xac0 fs/attr.c:398
 do_truncate fs/open.c:64 [inline]
 do_sys_ftruncate+0x2d9/0x390 fs/open.c:192
 __do_sys_ftruncate fs/open.c:203 [inline]
 __se_sys_ftruncate fs/open.c:201 [inline]
 __x64_sys_ftruncate+0x2f/0x40 fs/open.c:201
 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 0xffff888105301ad0 of 8 bytes by task 16854 on cpu 1:
 shmem_recalc_inode mm/shmem.c:364 [inline]
 shmem_getpage_gfp+0xfc9/0x13c0 mm/shmem.c:1945
 shmem_fault+0xcf/0x470 mm/shmem.c:2113
 __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+0xb8f/0x1530 mm/memory.c:4791
 faultin_page mm/gup.c:950 [inline]
 __get_user_pages+0x381/0xc50 mm/gup.c:1171
 populate_vma_page_range mm/gup.c:1503 [inline]
 __mm_populate+0x24d/0x380 mm/gup.c:1612
 mm_populate include/linux/mm.h:2616 [inline]
 vm_mmap_pgoff+0x142/0x1d0 mm/util.c:524
 ksys_mmap_pgoff+0x284/0x350 mm/mmap.c:1624
 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: 0x0000000000000914 -> 0x000000000000090b

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 16854 Comm: syz-executor.5 Tainted: G        W         5.14.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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