Hello, this is a second version of my patches to avoid clearing marks from xas_store() and thus fix regression in page cache truncation. Changes since v1 - rebased on 5.7-rc2 - drop xas_for_each_marked() fix as it was already merged - reworked the whole series based on Matthew's feedback - we now create new function xas_store_noinit() and use it instead of changing xas_store() behavior. Note that for xas_store_range() and __xa_cmpxchg() I didn't bother to change names although they stop clearing marks as well. This is because there are only very few callers so it's easy to verify them, also chances of a clash with other patch introducing new callers are very small. Original motivation: Conversion of page cache to xarray (commit 69b6c1319b6 "mm: Convert truncate to XArray" in particular) has regressed performance of page cache truncation by about 10% (see my original report here [1]). This patch series aims at improving the truncation to get some of that regression back. The first patch fixes a long standing bug with xas_for_each_marked() that I've uncovered when debugging my patches. The remaining patches then work towards the ability to stop clearing marks in xas_store() which improves truncation performance by about 6%. The patches have passed radix_tree tests in tools/testing and also fstests runs for ext4 & xfs. Honza [1] https://lore.kernel.org/linux-mm/20190226165628.GB24711@xxxxxxxxxxxxxx
