swap_pager: Unbusy readahead pages after an I/O error

[markj]

Summary

The swap pager itself allocates readahead pages, so should take care to
unbusy them after a read error, just as it does in the non-error case.

PR: 277538

[kib]

sys/vm/swap_pager.c

1689

Then why leave invalid pages on the object queue?
More, moving invalid pages to inactive queue does not sound right.

[markj]

sys/vm/swap_pager.c

1689

I think it's possible in principle for the page to be wired. So, the code needs to look like this:

if (!vm_page_wired(m) || vm_page_remove(m))
        vm_page_free(m);

It seemed more straightforward to just release the page to the head of the inactive queue (_noreuse) in this rare case. There is no problem with having invalid pages on the inactive queue.

[kib]

sys/vm/swap_pager.c

1689

There is vm_page_free_invalid()

[markj]

Use vm_page_free_invalid().