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BUG: KCSAN: data-race in ext4_mb_initialize_context / ext4_write_end

write to 0xffff88810d562c10 of 8 bytes by task 15110 on cpu 0:
 i_size_write include/linux/fs.h:871 [inline]
 ext4_update_inode_size fs/ext4/ext4.h:3260 [inline]
 ext4_write_end+0x1fe/0xa00 fs/ext4/inode.c:1301
 ext4_da_write_end+0x93/0x760 fs/ext4/inode.c:3071
 generic_perform_write+0x23e/0x3a0 mm/filemap.c:3340
 ext4_buffered_write_iter+0x2e5/0x3d0 fs/ext4/file.c:270
 ext4_file_write_iter+0x45e/0x1090 fs/ext4/file.c:503
 call_write_iter include/linux/fs.h:1903 [inline]
 do_iter_readv_writev+0x2cb/0x360 fs/read_write.c:740
 do_iter_write+0x112/0x4b0 fs/read_write.c:866
 vfs_iter_write+0x4c/0x70 fs/read_write.c:907
 iter_file_splice_write+0x42a/0x780 fs/splice.c:686
 do_splice_from fs/splice.c:764 [inline]
 direct_splice_actor+0x80/0xa0 fs/splice.c:933
 splice_direct_to_actor+0x345/0x650 fs/splice.c:888
 do_splice_direct+0xf5/0x170 fs/splice.c:976
 do_sendfile+0x5db/0xca0 fs/read_write.c:1257
 __do_sys_sendfile64 fs/read_write.c:1318 [inline]
 __se_sys_sendfile64 fs/read_write.c:1304 [inline]
 __x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1304
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88810d562c10 of 8 bytes by task 15113 on cpu 1:
 i_size_read include/linux/fs.h:849 [inline]
 ext4_mb_group_or_file fs/ext4/mballoc.c:4569 [inline]
 ext4_mb_initialize_context+0x2f5/0x4b0 fs/ext4/mballoc.c:4645
 ext4_mb_new_blocks+0x2d2/0x1140 fs/ext4/mballoc.c:4980
 ext4_ext_map_blocks+0x15a0/0x1fc0 fs/ext4/extents.c:4238
 ext4_map_blocks+0x700/0xfc0 fs/ext4/inode.c:628
 mpage_map_one_extent+0x10d/0x390 fs/ext4/inode.c:2387
 mpage_map_and_submit_extent fs/ext4/inode.c:2440 [inline]
 ext4_writepages+0xa41/0x1e30 fs/ext4/inode.c:2792
 do_writepages+0x7b/0x150 mm/page-writeback.c:2352
 __filemap_fdatawrite_range+0x19d/0x1d0 mm/filemap.c:422
 file_write_and_wait_range+0x9f/0x120 mm/filemap.c:761
 ext4_sync_file+0x105/0x6c0 fs/ext4/fsync.c:151
 vfs_fsync_range+0x107/0x120 fs/sync.c:200
 generic_write_sync include/linux/fs.h:2739 [inline]
 ext4_buffered_write_iter+0x384/0x3d0 fs/ext4/file.c:278
 ext4_file_write_iter+0x45e/0x1090 fs/ext4/file.c:503
 call_write_iter include/linux/fs.h:1903 [inline]
 do_iter_readv_writev+0x2cb/0x360 fs/read_write.c:740
 do_iter_write+0x112/0x4b0 fs/read_write.c:866
 vfs_iter_write+0x4c/0x70 fs/read_write.c:907
 iter_file_splice_write+0x42a/0x780 fs/splice.c:686
 do_splice_from fs/splice.c:764 [inline]
 direct_splice_actor+0x80/0xa0 fs/splice.c:933
 splice_direct_to_actor+0x345/0x650 fs/splice.c:888
 do_splice_direct+0xf5/0x170 fs/splice.c:976
 do_sendfile+0x5db/0xca0 fs/read_write.c:1257
 __do_sys_sendfile64 fs/read_write.c:1318 [inline]
 __se_sys_sendfile64 fs/read_write.c:1304 [inline]
 __x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1304
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 15113 Comm: syz-executor.0 Not tainted 5.10.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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