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BUG: KCSAN: data-race in ext4_alloc_file_blocks / ext4_mpage_readpages

write to 0xffff88813dd07ac8 of 8 bytes by task 23674 on cpu 1:
 i_size_write include/linux/fs.h:913 [inline]
 ext4_update_inode_size fs/ext4/ext4.h:3422 [inline]
 ext4_alloc_file_blocks+0x362/0x730 fs/ext4/extents.c:4493
 ext4_fallocate+0x2a7/0x540 fs/ext4/extents.c:4753
 vfs_fallocate+0x486/0x720 fs/open.c:307
 ksys_fallocate fs/open.c:330 [inline]
 __do_sys_fallocate fs/open.c:338 [inline]
 __se_sys_fallocate fs/open.c:336 [inline]
 __x64_sys_fallocate+0x75/0xc0 fs/open.c:336
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88813dd07ac8 of 8 bytes by task 23673 on cpu 0:
 i_size_read include/linux/fs.h:891 [inline]
 ext4_readpage_limit fs/ext4/readpage.c:221 [inline]
 ext4_mpage_readpages+0x395/0x1080 fs/ext4/readpage.c:265
 ext4_readahead+0x99/0xa0 fs/ext4/inode.c:3199
 read_pages+0xba/0x5f0 mm/readahead.c:129
 page_cache_ra_unbounded+0x3d2/0x430 mm/readahead.c:238
 do_page_cache_ra+0xa7/0xc0 mm/readahead.c:268
 do_sync_mmap_readahead+0x31c/0x370 mm/filemap.c:2996
 filemap_fault+0x267/0xa10 mm/filemap.c:3089
 __do_fault mm/memory.c:3849 [inline]
 do_shared_fault mm/memory.c:4219 [inline]
 do_fault mm/memory.c:4297 [inline]
 handle_pte_fault mm/memory.c:4551 [inline]
 __handle_mm_fault mm/memory.c:4686 [inline]
 handle_mm_fault+0xc78/0x1590 mm/memory.c:4784
 do_user_addr_fault+0x609/0xbe0 arch/x86/mm/fault.c:1397
 handle_page_fault arch/x86/mm/fault.c:1485 [inline]
 exc_page_fault+0x91/0x290 arch/x86/mm/fault.c:1541
 asm_exc_page_fault+0x1e/0x30

value changed: 0x00000000003d0000 -> 0x0000000000400000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 23673 Comm: syz-executor.3 Tainted: G        W         5.16.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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