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BUG: KCSAN: data-race in ext4_ext_index_trans_blocks / ext4_ext_insert_extent

write to 0xffff88802d4b8186 of 2 bytes by task 29207 on cpu 1:
 le16_add_cpu include/linux/byteorder/generic.h:146 [inline]
 ext4_ext_grow_indepth fs/ext4/extents.c:1330 [inline]
 ext4_ext_create_new_leaf fs/ext4/extents.c:1380 [inline]
 ext4_ext_insert_extent+0xc8c/0x2bc0 fs/ext4/extents.c:2054
 ext4_split_extent_at+0x6f2/0xb40 fs/ext4/extents.c:3208
 ext4_split_extent+0x134/0x2d0 fs/ext4/extents.c:3306
 ext4_split_convert_extents fs/ext4/extents.c:3665 [inline]
 ext4_ext_handle_unwritten_extents+0x1f4/0xac0 fs/ext4/extents.c:3827
 ext4_ext_map_blocks+0x728/0x1fd0 fs/ext4/extents.c:4119
 ext4_map_blocks+0x726/0xff0 fs/ext4/inode.c:638
 mpage_map_one_extent+0x10d/0x3a0 fs/ext4/inode.c:2397
 mpage_map_and_submit_extent fs/ext4/inode.c:2450 [inline]
 ext4_writepages+0xa51/0x1e70 fs/ext4/inode.c:2802
 do_writepages+0x7b/0x150 mm/page-writeback.c:2352
 __filemap_fdatawrite_range+0x19d/0x1d0 mm/filemap.c:424
 file_write_and_wait_range+0x9f/0x120 mm/filemap.c:763
 ext4_sync_file+0x105/0x6e0 fs/ext4/fsync.c:151
 vfs_fsync_range+0x107/0x120 fs/sync.c:200
 generic_write_sync include/linux/fs.h:2843 [inline]
 ext4_buffered_write_iter+0x38f/0x3e0 fs/ext4/file.c:277
 ext4_file_write_iter+0x48a/0x10b0 fs/ext4/file.c:502
 call_write_iter include/linux/fs.h:1977 [inline]
 do_iter_readv_writev+0x2cb/0x360 fs/read_write.c:740
 do_iter_write+0x112/0x4c0 fs/read_write.c:866
 vfs_iter_write+0x4c/0x70 fs/read_write.c:907
 iter_file_splice_write+0x40a/0x750 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+0xf5/0x170 fs/splice.c:979
 do_sendfile+0x7a6/0xe20 fs/read_write.c:1260
 __do_sys_sendfile64 fs/read_write.c:1319 [inline]
 __se_sys_sendfile64 fs/read_write.c:1311 [inline]
 __x64_sys_sendfile64+0xa9/0x130 fs/read_write.c:1311
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88802d4b8186 of 2 bytes by task 29204 on cpu 0:
 ext_depth fs/ext4/ext4_extents.h:193 [inline]
 ext4_ext_index_trans_blocks+0x86/0xb0 fs/ext4/extents.c:2356
 ext4_index_trans_blocks fs/ext4/inode.c:5617 [inline]
 ext4_meta_trans_blocks fs/ext4/inode.c:5643 [inline]
 ext4_da_writepages_trans_blocks fs/ext4/inode.c:2534 [inline]
 ext4_writepages+0x820/0x1e70 fs/ext4/inode.c:2782
 do_writepages+0x7b/0x150 mm/page-writeback.c:2352
 __filemap_fdatawrite_range+0x19d/0x1d0 mm/filemap.c:424
 filemap_write_and_wait_range+0x8b/0x2a0 mm/filemap.c:657
 __iomap_dio_rw+0x40a/0xa30 fs/iomap/direct-io.c:525
 iomap_dio_rw+0x30/0x70 fs/iomap/direct-io.c:641
 ext4_dio_write_iter fs/ext4/file.c:551 [inline]
 ext4_file_write_iter+0xe5d/0x10b0 fs/ext4/file.c:661
 call_write_iter include/linux/fs.h:1977 [inline]
 do_iter_readv_writev+0x2cb/0x360 fs/read_write.c:740
 do_iter_write+0x112/0x4c0 fs/read_write.c:866
 vfs_iter_write+0x4c/0x70 fs/read_write.c:907
 iter_file_splice_write+0x40a/0x750 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+0xf5/0x170 fs/splice.c:979
 do_sendfile+0x7a6/0xe20 fs/read_write.c:1260
 __do_sys_sendfile64 fs/read_write.c:1325 [inline]
 __se_sys_sendfile64 fs/read_write.c:1311 [inline]
 __x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1311
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 29204 Comm: syz-executor.2 Tainted: G        W         5.12.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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