==================================================================
BUG: KCSAN: data-race in ext4_alloc_file_blocks / mpage_process_page_bufs

write to 0xffff888059f01680 of 8 bytes by task 22633 on cpu 1:
 i_size_write include/linux/fs.h:871 [inline]
 ext4_update_inode_size fs/ext4/ext4.h:3141 [inline]
 ext4_alloc_file_blocks+0x325/0x6e0 fs/ext4/extents.c:4444
 ext4_fallocate+0x284/0x510 fs/ext4/extents.c:4696
 vfs_fallocate+0x43d/0x5d0 fs/open.c:309
 ksys_fallocate fs/open.c:332 [inline]
 __do_sys_fallocate fs/open.c:340 [inline]
 __se_sys_fallocate fs/open.c:338 [inline]
 __x64_sys_fallocate+0x75/0xc0 fs/open.c:338
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888059f01680 of 8 bytes by task 22631 on cpu 0:
 i_size_read include/linux/fs.h:849 [inline]
 mpage_process_page_bufs+0x34/0x5e0 fs/ext4/inode.c:2173
 mpage_prepare_extent_to_map+0x4d6/0x630 fs/ext4/inode.c:2607
 ext4_writepages+0x968/0x1e20 fs/ext4/inode.c:2779
 do_writepages+0x7b/0x150 mm/page-writeback.c:2352
 __filemap_fdatawrite_range+0x19d/0x1d0 mm/filemap.c:422
 __filemap_fdatawrite mm/filemap.c:430 [inline]
 filemap_flush+0x1f/0x30 mm/filemap.c:457
 ext4_alloc_da_blocks+0x4a/0x100 fs/ext4/inode.c:3145
 ext4_release_file+0x5b/0x1c0 fs/ext4/file.c:142
 __fput+0x243/0x4d0 fs/file_table.c:281
 ____fput+0x11/0x20 fs/file_table.c:314
 task_work_run+0x8e/0x110 kernel/task_work.c:141
 get_signal+0x3eb/0x1510 kernel/signal.c:2561
 arch_do_signal+0x25/0x270 arch/x86/kernel/signal.c:811
 exit_to_user_mode_loop kernel/entry/common.c:161 [inline]
 exit_to_user_mode_prepare+0x116/0x200 kernel/entry/common.c:192
 syscall_exit_to_user_mode+0x16/0x30 kernel/entry/common.c:267
 do_syscall_64+0x45/0x80 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 22631 Comm: syz-executor.3 Not tainted 5.9.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================