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>> XA_STATE(xas, &folio->mapping->i_pages, folio->index); >> @@ -3765,13 +3757,15 @@ static int __folio_split(struct folio *folio, unsigned int new_order, >> * is taken to serialise against parallel split or collapse >> * operations. >> */ >> - anon_vma = folio_get_anon_vma(folio); >> - if (!anon_vma) { >> - ret = -EBUSY; >> - goto out; >> + if (!unmapped) { >> + anon_vma = folio_get_anon_vma(folio); >> + if (!anon_vma) { >> + ret = -EBUSY; >> + goto out; >> + } >> + anon_vma_lock_write(anon_vma); >> } >> mapping = NULL; >> - anon_vma_lock_write(anon_vma); >> } else { >> unsigned int min_order; >> gfp_t gfp; >> @@ -3838,7 +3832,8 @@ static int __folio_split(struct folio *folio, unsigned int new_order, >> goto out_unlock; >> } >> >> - unmap_folio(folio); >> + if (!unmapped) >> + unmap_folio(folio); >> >> /* block interrupt reentry in xa_lock and spinlock */ >> local_irq_disable(); >> @@ -3925,10 +3920,13 @@ static int __folio_split(struct folio *folio, unsigned int new_order, >> >> next = folio_next(new_folio); >> >> + zone_device_private_split_cb(folio, new_folio); >> + >> expected_refs = folio_expected_ref_count(new_folio) + 1; >> folio_ref_unfreeze(new_folio, expected_refs); >> >> - lru_add_split_folio(folio, new_folio, lruvec, list); >> + if (!unmapped) >> + lru_add_split_folio(folio, new_folio, lruvec, list); >> >> /* >> * Anonymous folio with swap cache. >> @@ -3959,6 +3957,8 @@ static int __folio_split(struct folio *folio, unsigned int new_order, >> __filemap_remove_folio(new_folio, NULL); >> folio_put_refs(new_folio, nr_pages); >> } >> + >> + zone_device_private_split_cb(folio, NULL); >> /* >> * Unfreeze @folio only after all page cache entries, which >> * used to point to it, have been updated with new folios. >> @@ -3982,6 +3982,9 @@ static int __folio_split(struct folio *folio, unsigned int new_order, >> >> local_irq_enable(); >> >> + if (unmapped) >> + return ret; > > As the comment of __folio_split() and __split_huge_page_to_list_to_order() > mentioned: > > * The large folio must be locked > * After splitting, the after-split folio containing @lock_at remains locked > > But here we seems to change the prerequisites. > > Hmm.. I am not sure this is correct. > The code is correct, but you are right in that the documentation needs to be updated. When "unmapped", we do want to leave the folios locked after the split. Balbir