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    SubjectRe: [PATCH 05/14] vrange: Add new vrange(2) system call
    On 10/07/2013 04:14 PM, John Stultz wrote:
    >>
    >> I see from the change history of the patch that this was an madvise() at
    >> some point, but was changed into a separate system call at some point,
    >> does anyone remember why that was? A quick look through my LKML
    >> archives doesn't really make it clear.
    >
    > The reason we can't use madvise, is that to properly handle error cases
    > and report the pruge state, we need an extra argument.
    >
    > In much earlier versions, we just returned an error when setting
    > NONVOLATILE if the data was purged. However, since we have to possibly
    > do allocations when marking a range as non-volatile, we needed a way to
    > properly handle that allocation failing. We can't just return ENOMEM, as
    > we may have already marked purged memory as non-volatile.
    >
    > Thus, that's why with vrange, we return the number of bytes modified,
    > along with the purge state. That way, if an error does occur we can
    > return the purge state of the bytes successfully modified, and only
    > return an error if nothing was changed, much like when a write fails.
    >

    I am not clear at all what the "purge state" is in this case.

    -hpa




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