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BUG: KCSAN: data-race in ext4_file_write_iter / ext4_writepages

write to 0xffff888134936b58 of 8 bytes by task 10158 on cpu 0:
 mpage_map_and_submit_extent fs/ext4/inode.c:2495 [inline]
 ext4_writepages+0x137d/0x1d00 fs/ext4/inode.c:2804
 do_writepages+0x1db/0x350 mm/page-writeback.c:2352
 filemap_fdatawrite_wbc+0xd6/0xf0 mm/filemap.c:388
 __filemap_fdatawrite_range mm/filemap.c:421 [inline]
 file_write_and_wait_range+0xd6/0x170 mm/filemap.c:779
 ext4_sync_file+0x105/0x6d0 fs/ext4/fsync.c:151
 vfs_fsync_range+0x107/0x120 fs/sync.c:188
 generic_write_sync include/linux/fs.h:2732 [inline]
 ext4_buffered_write_iter+0x2ec/0x330 fs/ext4/file.c:277
 ext4_file_write_iter+0x2e3/0x1210
 call_write_iter include/linux/fs.h:2050 [inline]
 new_sync_write fs/read_write.c:504 [inline]
 vfs_write+0x71c/0x890 fs/read_write.c:591
 ksys_pwrite64 fs/read_write.c:698 [inline]
 __do_sys_pwrite64 fs/read_write.c:708 [inline]
 __se_sys_pwrite64 fs/read_write.c:705 [inline]
 __x64_sys_pwrite64+0xf5/0x150 fs/read_write.c:705
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888134936b58 of 8 bytes by task 10153 on cpu 1:
 ext4_handle_inode_extension fs/ext4/file.c:300 [inline]
 ext4_dio_write_iter fs/ext4/file.c:573 [inline]
 ext4_file_write_iter+0xb09/0x1210 fs/ext4/file.c:677
 do_iter_readv_writev+0x27b/0x300
 do_iter_write+0x16f/0x5c0 fs/read_write.c:852
 vfs_iter_write+0x4c/0x70 fs/read_write.c:893
 iter_file_splice_write+0x44a/0x7c0 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+0x345/0x660 fs/splice.c:891
 do_splice_direct+0xfb/0x180 fs/splice.c:979
 do_sendfile+0x3ad/0x900 fs/read_write.c:1246
 __do_sys_sendfile64 fs/read_write.c:1311 [inline]
 __se_sys_sendfile64 fs/read_write.c:1297 [inline]
 __x64_sys_sendfile64+0x10c/0x150 fs/read_write.c:1297
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x0000000000040000 -> 0x000004010000bffe

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 10153 Comm: syz-executor.3 Not tainted 5.18.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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