Linux-next: very slow disk write speed: WARNING: CPU: 4 PID: 12891 at fs/inode.c:390 ihold+0x30/0x40()

With the recent linux-next tree (e.g., next-20150909), I can easily get the below callstack (see the end of the mail) when I run some heavy I/O workloads, like building a kernel with "make -j16". After the callstack happens, "dd if=/dev/zero of=zero.bin bs=1M" shows the disk write speed goes

Linux-next: very slow disk write speed: WARNING: CPU: 4 PID: 12891 at fs/inode.c:390 ihold+0x30/0x40()

With the recent linux-next tree (e.g., next-20150909), I can easily get the below callstack (see the end of the mail) when I run some heavy I/O workloads, like building a kernel with "make -j16". After the callstack happens, "dd if=/dev/zero of=zero.bin bs=1M" shows the disk write speed goes