Messages in this thread | | | Date | Mon, 3 Feb 2014 13:41:01 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH 4/4] nilfs2: implementation of NILFS_IOCTL_SET_SUINFO ioctl |
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On Tue, 4 Feb 2014 01:50:44 +0900 Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp> wrote:
> With this ioctl the segment usage entries in the SUFILE can be > updated from userspace. > > This is useful, because it allows the userspace GC to modify and update > segment usage entries for specific segments, which enables it to avoid > unnecessary write operations. > > If a segment needs to be cleaned, but there is no or very little > reclaimable space in it, the cleaning operation basically degrades to > a useless moving operation. In the end the only thing that changes is > the location of the data and a timestamp in the segment usage > information. With this ioctl the GC can skip the cleaning and update > the segment usage entries directly instead. > > This is basically a shortcut to cleaning the segment. It is still > necessary to read the segment summary information, but the writing of > the live blocks can be skipped if it's not worth it.
Documentation/filesystems/nilfs2.txt should be updated to document the new ioctl.
Which we're in there, please check that the ioctl documentation is otherwise complete and up-to-date. These things have a tendency to bitrot.
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