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

write to 0xffff888104b22198 of 8 bytes by task 8387 on cpu 1:
 i_size_write include/linux/fs.h:916 [inline]
 generic_write_end+0x96/0x180 fs/buffer.c:2186
 fat_write_end+0x4a/0x160 fs/fat/inode.c:249
 generic_perform_write+0x251/0x3e0 mm/filemap.c:3781
 __generic_file_write_iter+0x174/0x310 mm/filemap.c:3897
 generic_file_write_iter+0x75/0x130 mm/filemap.c:3929
 call_write_iter include/linux/fs.h:2163 [inline]
 do_iter_readv_writev+0x2de/0x380 fs/read_write.c:729
 do_iter_write+0x192/0x5c0 fs/read_write.c:855
 vfs_iter_write+0x4c/0x70 fs/read_write.c:896
 iter_file_splice_write+0x43a/0x790 fs/splice.c:689
 do_splice_from fs/splice.c:767 [inline]
 direct_splice_actor+0x80/0xa0 fs/splice.c:936
 splice_direct_to_actor+0x345/0x650 fs/splice.c:891
 do_splice_direct+0x106/0x190 fs/splice.c:979
 do_sendfile+0x63e/0xbb0 fs/read_write.c:1249
 __do_sys_sendfile64 fs/read_write.c:1314 [inline]
 __se_sys_sendfile64 fs/read_write.c:1300 [inline]
 __x64_sys_sendfile64+0x102/0x140 fs/read_write.c:1300
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888104b22198 of 8 bytes by task 8399 on cpu 0:
 i_size_read include/linux/fs.h:894 [inline]
 block_write_full_page+0x41/0x260 fs/buffer.c:2956
 fat_writepage+0x20/0x30 fs/fat/inode.c:199
 __mpage_writepage+0xd08/0x10c0 fs/mpage.c:660
 write_cache_pages+0x50a/0x840 mm/page-writeback.c:2255
 mpage_writepages+0x7f/0x130 fs/mpage.c:712
 fat_writepages+0x20/0x30 fs/fat/inode.c:205
 do_writepages+0x26b/0x3c0 mm/page-writeback.c:2364
 filemap_fdatawrite_wbc mm/filemap.c:400 [inline]
 __filemap_fdatawrite_range mm/filemap.c:433 [inline]
 file_write_and_wait_range+0x1ae/0x240 mm/filemap.c:810
 __generic_file_fsync+0x48/0x140 fs/libfs.c:1088
 fat_file_fsync+0x48/0x100 fs/fat/file.c:190
 vfs_fsync_range+0x107/0x120 fs/sync.c:200
 generic_write_sync include/linux/fs.h:2955 [inline]
 generic_file_write_iter+0x103/0x130 mm/filemap.c:3933
 call_write_iter include/linux/fs.h:2163 [inline]
 do_iter_readv_writev+0x2de/0x380 fs/read_write.c:729
 do_iter_write+0x192/0x5c0 fs/read_write.c:855
 vfs_iter_write+0x4c/0x70 fs/read_write.c:896
 iter_file_splice_write+0x43a/0x790 fs/splice.c:689
 do_splice_from fs/splice.c:767 [inline]
 direct_splice_actor+0x80/0xa0 fs/splice.c:936
 splice_direct_to_actor+0x345/0x650 fs/splice.c:891
 do_splice_direct+0x106/0x190 fs/splice.c:979
 do_sendfile+0x63e/0xbb0 fs/read_write.c:1249
 __do_sys_sendfile64 fs/read_write.c:1314 [inline]
 __se_sys_sendfile64 fs/read_write.c:1300 [inline]
 __x64_sys_sendfile64+0x102/0x140 fs/read_write.c:1300
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x0000000000008200 -> 0x0000000000008282

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 8399 Comm: syz-executor.2 Not tainted 5.15.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================
syz-executor.2 (8399) used greatest stack depth: 10560 bytes left