It's nice to see a primitive like this making it into mainline Linux. We did something similar for the Itsy handheld back around 2000-2001. Itsy had flash on the motherboard with its own drivers, so we didn't need to wait for anything to be added to the SCSI or ATA interfaces before the idea could be used. I don't think reordering of discards vs. writes was possible with our flash drivers. See: http://tim-mann.org/papers/hamburgen01itsy.pdf http://tim-mann.org/papers/SRC-TN-2001-001.pdf Even earlier than that, the Petal distributed virtual disk had a discard primitive and the Frangipani filesystem built on top of it used it. Conventional filesystems could run on Petal too, but would used disk space more efficiently if modified to use the discard primitive. http://tim-mann.org/papers/frangipani.pdf http://portal.acm.org/citation.cfm?id=237157 Basically, this primitive is good for most kinds of virtual disk, to allow savings of one kind or another if the virtual disk is informed that it can throw some data away. I was always kind of surprised it didn't make it into standard OSes long ago.
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