Hi Omar Sandoval, On Sat, Dec 1, 2018 at 4:56 AM Omar Sandoval <osandov@xxxxxxxxxxx> wrote: > > On Fri, Nov 30, 2018 at 04:32:40AM -0500, Huijin Park wrote: > > From: "huijin.park" <huijin.park@xxxxxxxxxxx> > > > > This patch changes the 'sectors' type to an u64. > > In 32 bit system, the 'sectors' can accumulate up to about 2TiB. > > If a 32 bit system makes i/o over 2TiB while running, > > the 'sectors' will overflow. > > As a result, the part_stat_read(sectors), the diskstats in proc and > > the (lifetime|session)_write_kbytes in sysfs return invalid statistic. > > What about parsers which expect it to be an unsigned long? E.g., iostat: > https://github.com/sysstat/sysstat/blob/v12.1.1/rd_stats.c#L736 > > At least with glibc, scanf seems to truncate sanely, but this appears to > be undefined. The glibc APIs such as scanf and strtoul set return value and errno to ULONG_MAX and ERANGE in overflow case. I think ULONG_MAX and ERANGE are better than reset to zero because of overflow. At least, application can notice overflow with errno. Besides nowadays, a 32 bit is not enough size to show an i/o accumulated size. I met a problem like below. So I suggested this patch. sh-3.2# mount | grep p19 /dev/mmcblk0p19 on /ext4_dir type ext4 (rw,relatime,data=ordered) sh-3.2# cat /sys/fs/ext4/mmcblk0p19/session_write_kbytes 2147467268 sh-3.2# cat /sys/fs/ext4/mmcblk0p19/lifetime_write_kbytes 2147568561 sh-3.2# dd if=/dev/zero of=/ext4_dir/temp.bin bs=1M count=20 oflag=sync 20+0 records in 20+0 records out 20971520 bytes (21 MB) copied, 0.621939 s, 33.7 MB/s sh-3.2# cat /sys/fs/ext4/mmcblk0p19/session_write_kbytes 4524 sh-3.2# cat /sys/fs/ext4/mmcblk0p19/lifetime_write_kbytes 105817 > > > Signed-off-by: huijin.park <huijin.park@xxxxxxxxxxx> > > --- > > block/genhd.c | 6 +++--- > > include/linux/genhd.h | 2 +- > > 2 files changed, 4 insertions(+), 4 deletions(-) > > > > diff --git a/block/genhd.c b/block/genhd.c > > index 0145bcb..7518dcd 100644 > > --- a/block/genhd.c > > +++ b/block/genhd.c > > @@ -1343,10 +1343,10 @@ static int diskstats_show(struct seq_file *seqf, void *v) > > part_stat_unlock(); > > part_in_flight(gp->queue, hd, inflight); > > seq_printf(seqf, "%4d %7d %s " > > - "%lu %lu %lu %u " > > - "%lu %lu %lu %u " > > + "%lu %lu %llu %u " > > + "%lu %lu %llu %u " > > "%u %u %u " > > - "%lu %lu %lu %u\n", > > + "%lu %lu %llu %u\n", > > MAJOR(part_devt(hd)), MINOR(part_devt(hd)), > > disk_name(gp, hd->partno, buf), > > part_stat_read(hd, ios[STAT_READ]), > > diff --git a/include/linux/genhd.h b/include/linux/genhd.h > > index 0c5ee17..5bf86f9 100644 > > --- a/include/linux/genhd.h > > +++ b/include/linux/genhd.h > > @@ -84,7 +84,7 @@ struct partition { > > > > struct disk_stats { > > u64 nsecs[NR_STAT_GROUPS]; > > - unsigned long sectors[NR_STAT_GROUPS]; > > + u64 sectors[NR_STAT_GROUPS]; > > unsigned long ios[NR_STAT_GROUPS]; > > unsigned long merges[NR_STAT_GROUPS]; > > unsigned long io_ticks; > > -- > > 1.7.9.5 > > Thanks, Huijin
