On Tue, Jun 17, 2014 at 6:00 AM, Lukáš Czerner [off-list ref] wrote:

What is the difference between -o discard mount option ?

Android will not mount -o discard because of the overall penalty.

I guess
that this way you can do it selectively on certain files, but I
wonder how useful it is going to be anyway ?

For certain files only. Useful enough.

If they are ok with only best effort, then we can have FISTRIM ioctl
which would use the same internal file system functionality as
FITRIM but we would add a flag to be able to call sb_issue_discard()
with BLKDEV_DISCARD_SECURE flag,

I think this was the idea of the original patch.

disable the optimization to skip
already discarded groups and call sync on the file system before we
start doing any actuall work.

That would need adding to the original patch.

If we do this though we should not add word "security" anywhere for
the use to see :)

We can live with that.
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