Hi,
I was using kernel 4.14, and latest version of mdadm cloning from github
this situation can only happen with *super 1.0*
The initial value of rdev->sectors (1933615488 ) was assigned in function
super_1_load in kernel while created with the value of sb->data_size, which is
"sectors in this device that can be used for data" comment in super1.c
of mdadm source code. So I think the value is right and does not
represent 5G capacity.
But this is also what I'm confused, why would mdadm set the value of "it is about to use" to the
variable of "it can be used in this device"? In this case, I didn't use full space in the first place,
and after the first growing, still not using full space. rdev->sectors became the size I wanted
to use, so "sectors in this device that can be used for data" became "sectors used for data now",
there's no way I can grow this array again.
Thanks,
‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On March 29, 2018 4:57 PM, Guoqing Jiang <gqjiang@xxxxxxxx> wrote:
> On 03/29/2018 09:45 AM, Fisher wrote:
>
> > Hi,
> >
> > I have a raid1 array composed with 2 disks which has 931GB size
> >
> > At first, I created this array with --size=5G and --metadata=1.0 set
> >
> > after that I grew the array to --size=10G and it succeed.
> >
> > Then I grew the array again to --size=20G
> >
> > but it failed this time with the following message
> >
> > mdadm: Cannot set device size for /dev/md0: No space left on device
> >
> > after I traced the code, I found it was because the following code
> >
> > int Grow_reshape(char *devname, int fd, int quiet, char backup_file,/ skip */
> >
> > for (mdi = sra->devs; mdi; mdi = mdi->next) {
> >
> > sysfs_set_num(sra, mdi, "size", s->size == MAX_SIZE ? 0
> >
> > : s->size);
> >
> > this changed the value of rdev->size from 1933615488 to 20971520 at first grow
> >
> > but second grow was limited by kernel when mdadm tried to set 41943040 to size
>
> 20971520 and 41943040 can match 10G and 20G well, but how 1933615488
>
> could represent 5G capacity?
>
> > static unsigned long long
> >
> > super_1_rdev_size_change(struct md_rdev rdev, sector_t num_sectors)/ skip */
> >
> > max_sectors = rdev->sectors + sb_start - rdev->sb_start;
> >
> > ^^^^^^^^^^^^^
> >
> > 20971520
> >
> > if (!num_sectors || num_sectors > max_sectors)
> >
> > num_sectors = max_sectors;
> >
> > seems like there's no way this array can be grown again.
>
> Which kernel version are you used? I can't reproduce it with 4.16.0-rc1.
>
> Thanks,
>
> Guoqing
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