Anton Blanchard wrote:
Hi,
The advantage would be that it wouldn't require a v3 for platforms for
which MIN_PAGE_SIZE == PAGE_SIZE, which accounts for a very large
percentage of systems.
You still have to look for the darn magic in two places, so there is no
reason for it to be different.
The problem is if you can hit in two places then what PAGE_SIZE should
you use to size the contents of the swap header while remaining backward
compatible.
Im leaning towards Dave suggestion of creating a clean v3 swap header.
Changing the header format doesn't make *ANY* difference whatsoever.
You have to write two copies of the swap header, and the kernel should
check for a header at MIN_PAGE_SIZE first and then at PAGE_SIZE.
If there are fields (other than position) in the v2 swap header that are
dependent on PAGE_SIZE, then the copy at MIN_PAGE_SIZE should be sized
using MIN_PAGE_SIZE, and the copy at PAGE_SIZE should be sized at
PAGE_SIZE. It's that simple.
Creating a new format will not help that one iota, and will create
gratuitous incompatiblity for the very common case of PAGE_SIZE ==
MIN_PAGE_SIZE.
-hpa
-hpa
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