==================================================================
BUG: KCSAN: data-race in __mpage_writepage / generic_write_end

write to 0xffff8881089d9318 of 8 bytes by task 8813 on cpu 1:
 i_size_write include/linux/fs.h:932 [inline]
 generic_write_end+0x94/0x230 fs/buffer.c:2275
 fat_write_end+0x4e/0x160 fs/fat/inode.c:244
 cont_expand_zero fs/buffer.c:2497 [inline]
 cont_write_begin+0x2c0/0x690 fs/buffer.c:2555
 fat_write_begin+0x61/0xf0 fs/fat/inode.c:230
 generic_cont_expand_simple+0xa7/0x140 fs/buffer.c:2456
 fat_cont_expand+0x3a/0x160 fs/fat/file.c:223
 fat_fallocate+0x182/0x1d0 fs/fat/file.c:301
 vfs_fallocate+0x378/0x3e0 fs/open.c:328
 ksys_fallocate fs/open.c:351 [inline]
 __do_sys_fallocate fs/open.c:359 [inline]
 __se_sys_fallocate fs/open.c:357 [inline]
 __x64_sys_fallocate+0x79/0xc0 fs/open.c:357
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x59/0x120 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff8881089d9318 of 8 bytes by task 8814 on cpu 0:
 i_size_read include/linux/fs.h:910 [inline]
 __mpage_writepage+0xa6/0xdc0 fs/mpage.c:478
 write_cache_pages+0x38d/0x740 mm/page-writeback.c:2474
 mpage_writepages+0x72/0xe0 fs/mpage.c:672
 fat_writepages+0x24/0x30 fs/fat/inode.c:200
 do_writepages+0x1c2/0x340 mm/page-writeback.c:2553
 filemap_fdatawrite_wbc+0xdb/0xf0 mm/filemap.c:388
 __filemap_fdatawrite_range mm/filemap.c:421 [inline]
 file_write_and_wait_range+0xf4/0x190 mm/filemap.c:779
 __generic_file_fsync+0x4c/0x140 fs/libfs.c:1438
 fat_file_fsync+0x4c/0x100 fs/fat/file.c:191
 vfs_fsync_range+0x111/0x120 fs/sync.c:188
 generic_write_sync include/linux/fs.h:2735 [inline]
 generic_file_write_iter+0x191/0x1c0 mm/filemap.c:4055
 call_write_iter include/linux/fs.h:2085 [inline]
 aio_write+0x301/0x420 fs/aio.c:1628
 io_submit_one+0xb39/0x1250 fs/aio.c:2047
 __do_sys_io_submit fs/aio.c:2106 [inline]
 __se_sys_io_submit+0xf5/0x280 fs/aio.c:2076
 __x64_sys_io_submit+0x43/0x50 fs/aio.c:2076
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x59/0x120 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0x000000000004f000 -> 0x0000000000050000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 8814 Comm: syz-executor.1 Not tainted 6.8.0-rc1-syzkaller-00029-g615d30064886 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
==================================================================