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BUG: KCSAN: data-race in filemap_map_pages / generic_write_end

write to 0xffff88813586f190 of 8 bytes by task 13969 on cpu 0:
 i_size_write include/linux/fs.h:871 [inline]
 generic_write_end+0x98/0x250 fs/buffer.c:2186
 ext4_da_write_end+0x59b/0x760 fs/ext4/inode.c:3102
 generic_perform_write+0x23e/0x3a0 mm/filemap.c:3340
 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:1903 [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

read to 0xffff88813586f190 of 8 bytes by task 13970 on cpu 1:
 i_size_read include/linux/fs.h:849 [inline]
 filemap_map_pages+0x481/0x9a0 mm/filemap.c:2876
 do_fault_around mm/memory.c:3967 [inline]
 do_read_fault+0x233/0x760 mm/memory.c:4001
 do_fault mm/memory.c:4134 [inline]
 handle_pte_fault mm/memory.c:4374 [inline]
 __handle_mm_fault mm/memory.c:4509 [inline]
 handle_mm_fault+0xfeb/0x1770 mm/memory.c:4607
 faultin_page mm/gup.c:885 [inline]
 __get_user_pages+0x8ec/0xe50 mm/gup.c:1097
 populate_vma_page_range mm/gup.c:1430 [inline]
 __mm_populate+0x24d/0x340 mm/gup.c:1478
 mm_populate include/linux/mm.h:2590 [inline]
 vm_mmap_pgoff+0x133/0x170 mm/util.c:512
 ksys_mmap_pgoff+0x2a8/0x380 mm/mmap.c:1634
 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: 13970 Comm: syz-executor.2 Not tainted 5.10.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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