biosnoop: show partition number

`biosnoop-bpfcc` (as of Debian buster, package bpfcc-tools=0.8.0-4; can't get the [current upstream version biosnoop.py](https://github.com/iovisor/bcc/blob/master/tools/biosnoop.py) to compile) will only print the disk name, but not the partition number:

```
host ~ # biosnoop-bpfcc | head
TIME(s) COMM PID DISK T SECTOR BYTES LAT(ms)
0.000000000 smbd 23977 sda W 16217088 4096 0.08
0.000036000 smbd 23977 sdb W 16217088 4096 0.11
0.000306000 smbd 23977 sda W 145944280 4096 0.39
0.000315000 smbd 23977 sdb W 145944280 4096 0.39
0.000623000 smbd 23977 sdb W 145944400 4096 0.69
0.000655000 smbd 23977 sda W 145944400 4096 0.73
0.000720000 smbd 23977 sdb W 2243599032 8192 0.79
0.000729000 smbd 23977 sda W 2243599032 8192 0.81
0.001038000 smbd 23977 sdb W 2243599408 4096 1.11
```

I needed to figure out which process was accessing `/dev/sd[ab]1`, so this wasn't immediately useful. I haphazardly hacked partition number output into the code:

``` diff
host ~ # diff -u =biosnoop-bpfcc biosnoop-bpfcc
--- /usr/sbin/biosnoop-bpfcc 2019-02-04 11:10:29.000000000 +0100
+++ biosnoop-bpfcc 2021-03-10 12:46:32.225811209 +0100
@@ -35,6 +35,7 @@
u64 sector;
u64 len;
u64 ts;
+ u8 part_no;
char disk_name[DISK_NAME_LEN];
char name[TASK_COMM_LEN];
};
@@ -97,6 +98,7 @@
struct gendisk *rq_disk = req->rq_disk;
bpf_probe_read(&data.disk_name, sizeof(data.disk_name),
rq_disk->disk_name);
+ data.part_no = req->part->partno;
}

/*
@@ -139,6 +141,7 @@
("sector", ct.c_ulonglong),
("len", ct.c_ulonglong),
("ts", ct.c_ulonglong),
+ ("part_no", ct.c_uint8),
("disk_name", ct.c_char * DISK_NAME_LEN),
("name", ct.c_char * TASK_COMM_LEN)
]
@@ -178,7 +181,7 @@

print("%-14.9f %-14.14s %-6s %-7s %-2s %-9s %-7s %7.2f" % (
delta / 1000000, event.name.decode('utf-8', 'replace'), event.pid,
- event.disk_name.decode('utf-8', 'replace'), rwflg, val,
+ event.disk_name.decode('utf-8', 'replace') + str(event.part_no), rwflg, val,
event.len, float(event.delta) / 1000000))

prev_ts = event.ts
```

This worked for me:

```
host ~ # ./biosnoop-bpfcc | grep 'sd[ab]1'
45.523952000 lvs 2437 sda1 R 2048 131072 23.39
45.531841000 lvs 2437 sdb1 R 2048 131072 31.20
348.280517000 lvs 20464 sdb1 R 2048 131072 11.90
348.300381000 lvs 20464 sda1 R 2048 131072 18.11
651.168481000 lvs 4241 sda1 R 2048 131072 9.87
651.170764000 lvs 4241 sdb1 R 2048 131072 20.18
792.194199000 lvs 13309 sda1 R 2048 131072 15.38
792.211849000 lvs 13309 sdb1 R 2048 131072 32.82
874.594627000 lvs 16563 sda1 R 2048 131072 39.51
874.669798000 lvs 16563 sdb1 R 2048 131072 114.56
957.403398000 lvs 21855 sda1 R 2048 131072 12.58
957.411141000 lvs 21855 sdb1 R 2048 131072 20.15
1260.488296000 lvs 11923 sda1 R 2048 131072 9.65
1260.501561000 lvs 11923 sdb1 R 2048 131072 26.41
1563.048093000 lvs 29968 sda1 R 2048 131072 13.93
1563.083581000 lvs 29968 sdb1 R 2048 131072 49.34
1865.624004000 lvs 2918 sdb1 R 2048 131072 30.23
1865.624663000 lvs 2918 sda1 R 2048 131072 26.18
```

Start with the current upstream biosnoop.py linked in the issue and compare its event structure, partition handling, and output formatting with the provided diff. Run biosnoop-bpfcc against partitioned devices and verify that the displayed disk names include the partition number, such as sda1 and sdb1.

Written by the indexing model from the issue text.