Re: Retrieving number of free unused eraseblocks in a UBI filesystem

[Boris Brezillon <boris.brezillon@free-electrons.com>]

On Wed, 7 Dec 2016 13:07:25 +0000
Martin Townsend <mtownsend1973@gmail.com> wrote:

> On Wed, Dec 7, 2016 at 12:39 PM, Boris Brezillon
> <boris.brezillon@free-electrons.com> wrote:
> > On Wed, 7 Dec 2016 11:59:13 +0000
> > Martin Townsend <mtownsend1973@gmail.com> wrote:
> >  
> >> Hi,
> >>
> >> I'm running a 4.1 Kernel and have a UBI Filesystem with 2 volumes
> >> taking up all the NAND.
> >> ubinfo -d 0
> >> ubi0
> >> Volumes count:                           2
> >> Logical eraseblock size:                 126976 bytes, 124.0 KiB
> >> Total amount of logical eraseblocks:     4016 (509935616 bytes, 486.3 MiB)
> >> Amount of available logical eraseblocks: 0 (0 bytes)
> >> Maximum count of volumes                 128
> >> Count of bad physical eraseblocks:       56
> >> Count of reserved physical eraseblocks:  24
> >> Current maximum erase counter value:     15
> >> Minimum input/output unit size:          2048 bytes
> >> Character device major/minor:            249:0
> >> Present volumes:                         0, 1
> >>
> >> So I'm guessing that the Total amount of logical erase blocks is 0 as
> >> this is because I have 2 volumes of a fixed size that take up all the
> >> available eraseblocks of the /dev/ubi0 device.
> >>
> >> Is there a way of getting, per volume preferably, the number of
> >> eraseblocks that aren't being used? Or conversely get the number of
> >> eraseblocks that are used as I can work it out from the total amount
> >> of logical eraseblocks.  
> >
> > cat /sys/class/ubi/ubiX_Y/reserved_ebs
> >
> > where X is the UBI device id and Y is the volume id.
> >  
> 
> Thanks for the swift reply, this seems to give me the total number of
> eraseblocks:
> 
> # cat /sys/class/ubi/ubi0_1/reserved_ebs
> 3196
> 
> # ubinfo -d0 -n1
> Volume ID:   1 (on ubi0)
> Type:        dynamic
> Alignment:   1
> Size:        3196 LEBs (405815296 bytes, 387.0 MiB)
> State:       OK
> Name:        rootfs
> 
> # df -h .
> Filesystem      Size  Used Avail Use% Mounted on
> ubi0:rootfs     357M  135M  222M  38% /
> 
> What I would like to know is how many of them are being used and how
> many are not.

Well, for static volumes, you could extract this information from the
data_bytes sysfs file. It doesn't work for dynamic volumes though, but
even if you could extract this information from the number of mapped
LEBs, not sure it would have any meaning, because unmapped LEBs can
still be reserved by the upper layer, and just because you have a lot
of unmapped LEBs does not mean you can shrink the volume (which I guess
is your ultimate goal).

> 
> >>
> >> Many Thanks,
> >> Martin.
> >>
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> >