> > @@ -1608,14 +1598,12 @@ bool zswap_store(struct folio *folio)
> > /* map */
> > spin_lock(&tree->lock);
> > /*
> > - * A duplicate entry should have been removed at the beginning of this
> > - * function. Since the swap entry should be pinned, if a duplicate is
> > - * found again here it means that something went wrong in the swap
> > - * cache.
> > + * The folio may have been dirtied again, invalidate the
> > + * possibly stale entry before inserting the new entry.
> > */
> > - while (zswap_rb_insert(&tree->rbroot, entry, &dupentry) == -EEXIST) {
> > - WARN_ON(1);
> > + if (zswap_rb_insert(&tree->rbroot, entry, &dupentry) == -EEXIST) {
> > zswap_invalidate_entry(tree, dupentry);
> > + VM_WARN_ON(zswap_rb_insert(&tree->rbroot, entry, &dupentry));
>
> It seems there is only one path called zswap_rb_insert() and there is
> no loop to repeat the insert any more. Can we have the
> zswap_rb_insert() install the entry and return the dupentry? We can
> still just call zswap_invalidate_entry() on the duplicate. The mapping
> of the dupentry has been removed when zswap_rb_insert() returns. That
> will save a repeat lookup on the duplicate case.
> After this change, the zswap_rb_insert() will map to the xarray
> xa_store() pretty nicely.
I brought this up in v1 [1]. We agreed to leave it as-is for now since
we expect the xarray conversion soon-ish. No need to update
zswap_rb_insert() only to replace it with xa_store() later anyway.
[1] https://lore.kernel.org/lkml/ZcFne336KJdbrvvS@xxxxxxxxxx/
