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BUG: KCSAN: data-race in __mpage_writepage / generic_file_direct_write

write to 0xffff8881083f4a00 of 8 bytes by task 6731 on cpu 1:
 i_size_write include/linux/fs.h:932 [inline]
 generic_file_direct_write+0x19d/0x1f0 mm/filemap.c:3870
 __generic_file_write_iter+0xae/0x120 mm/filemap.c:3999
 generic_file_write_iter+0x7d/0x1c0 mm/filemap.c:4039
 do_iter_write+0x4ad/0x770 fs/read_write.c:860
 vfs_iter_write+0x56/0x70 fs/read_write.c:901
 iter_file_splice_write+0x462/0x7e0 fs/splice.c:736
 do_splice_from fs/splice.c:933 [inline]
 direct_splice_actor+0x8a/0xb0 fs/splice.c:1142
 splice_direct_to_actor+0x31d/0x690 fs/splice.c:1088
 do_splice_direct+0x10d/0x190 fs/splice.c:1194
 do_sendfile+0x3c4/0x980 fs/read_write.c:1254
 __do_sys_sendfile64 fs/read_write.c:1322 [inline]
 __se_sys_sendfile64 fs/read_write.c:1308 [inline]
 __x64_sys_sendfile64+0x110/0x150 fs/read_write.c:1308
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff8881083f4a00 of 8 bytes by task 6732 on cpu 0:
 i_size_read include/linux/fs.h:910 [inline]
 __mpage_writepage+0xc0/0xd90 fs/mpage.c:488
 write_cache_pages+0x38d/0x740 mm/page-writeback.c:2474
 mpage_writepages+0x72/0xe0 fs/mpage.c:678
 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:387
 __filemap_fdatawrite_range mm/filemap.c:420 [inline]
 file_write_and_wait_range+0xf4/0x190 mm/filemap.c:778
 __generic_file_fsync+0x4c/0x140 fs/libfs.c:1440
 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:2653 [inline]
 generic_file_write_iter+0x191/0x1c0 mm/filemap.c:4043
 do_iter_write+0x4ad/0x770 fs/read_write.c:860
 vfs_iter_write+0x56/0x70 fs/read_write.c:901
 iter_file_splice_write+0x462/0x7e0 fs/splice.c:736
 do_splice_from fs/splice.c:933 [inline]
 direct_splice_actor+0x8a/0xb0 fs/splice.c:1142
 splice_direct_to_actor+0x31d/0x690 fs/splice.c:1088
 do_splice_direct+0x10d/0x190 fs/splice.c:1194
 do_sendfile+0x3c4/0x980 fs/read_write.c:1254
 __do_sys_sendfile64 fs/read_write.c:1322 [inline]
 __se_sys_sendfile64 fs/read_write.c:1308 [inline]
 __x64_sys_sendfile64+0x110/0x150 fs/read_write.c:1308
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0x000000000003a200 -> 0x000000000003a400

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 6732 Comm: syz-executor.0 Not tainted 6.6.0-syzkaller-15156-g13d88ac54ddd #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023
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