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Donenfeld" To: David Hildenbrand Cc: Linus Torvalds , linux-kernel@vger.kernel.org, patches@lists.linux.dev, tglx@linutronix.de, linux-crypto@vger.kernel.org, linux-api@vger.kernel.org, x86@kernel.org, Greg Kroah-Hartman , Adhemerval Zanella Netto , Carlos O'Donell , Florian Weimer , Arnd Bergmann , Jann Horn , Christian Brauner , David Hildenbrand , linux-mm@kvack.org Subject: Re: [PATCH v22 1/4] mm: add MAP_DROPPABLE for designating always lazily freeable mappings Message-ID: References: <98798483-dfcd-451e-94bb-57d830bf68d8@redhat.com> <54b6de32-f127-4928-9f4a-acb8653e5c81@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: C01C51C0011 X-Stat-Signature: mzsrrmszmbrqpwp5z79yaarhasdpfqnw X-Rspam-User: X-HE-Tag: 1720721869-204792 X-HE-Meta: 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 0oMLHwn5 DP0UNEwPyP2oRLXs9C6u/sY3CQA0uywl+fo4m7/UfsJl00D1iMG/Ni0aaE42goANlpTpnp6geh2KBVpBt2YYtb/+EeYJqbpMjj2/ScQGlu00wn9tf1VcsHjTWgjr//l7zHMauLctiQ5lHa1jwYHVIPSd/17T6A+zPhFVkTAPcRLn70Ki8foZAu8JMCDIdDKhBUlphZM3I/y0Xf04fFff2oeABSweVp36Pv+OpN4CmFe7XR1RP6KidlNlQumMMiK22gwVm3KwFKKN+9C9sV0chyDBijJKVZ9ZcdUGlZHkoALE82fbtzNzums/7G6F4CzG9QbBRTGgXogSf4x3xhKbSG4DGvGpOjEVk1AemL1ij3Bdf0hkGmWZZYl9S+nFDsDomexF2nh1yRR2y0PtkI28bvOr8bdvXVurRmE6aS9BBWsHgx8hcfNoutD094vCMexPs85A3XshDJcum6Fc= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Jul 11, 2024 at 07:56:39PM +0200, Jason A. Donenfeld wrote: > On Thu, Jul 11, 2024 at 07:54:34PM +0200, Jason A. Donenfeld wrote: > > On Thu, Jul 11, 2024 at 07:27:27PM +0200, David Hildenbrand wrote: > > > > PG_owner_priv_1 maps to PG_swapcache? :) > > > > > > Maybe the combination !swapbacked && swapcache could be used to indicate > > > such folios. (we will never set swapbacked) > > > > > > But likely we have to be a bit careful here. We don't want > > > folio_test_swapcache() to return for folios that ... are not in the > > > swapcache. > > > > I was thinking that too, but I'm afraid it's going to be another > > whack-a-mole nightmare. Even for things like task_mmu in procfs that > > show stats, that's going to be wonky. > > > > Any other flags we can overload that aren't going to be already used in > > our case? > > PG_error / folio_set_error seems unused in the non-IO case. And PG_large_rmappable seems to only be used for hugetlb branches. diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index b9e914e1face..7fdc03197438 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -190,6 +190,7 @@ enum pageflags { /* At least one page in this folio has the hwpoison flag set */ PG_has_hwpoisoned = PG_error, PG_large_rmappable = PG_workingset, /* anon or file-backed */ + PG_droppable = PG_error, /* anon droppable, not hugetlb */ }; #define PAGEFLAGS_MASK ((1UL << NR_PAGEFLAGS) - 1) @@ -640,6 +641,8 @@ FOLIO_TEST_CLEAR_FLAG_FALSE(young) FOLIO_FLAG_FALSE(idle) #endif +FOLIO_FLAG(droppable, FOLIO_SECOND_PAGE) + /* * PageReported() is used to track reported free pages within the Buddy * allocator. We can use the non-atomic version of the test and set diff --git a/mm/rmap.c b/mm/rmap.c index 1f9b5a9cb121..73b4052b2f82 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1403,6 +1403,8 @@ void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma, */ if (!(vma->vm_flags & VM_DROPPABLE)) __folio_set_swapbacked(folio); + else + folio_set_droppable(folio); __folio_set_anon(folio, vma, address, true); if (likely(!folio_test_large(folio))) { @@ -1852,7 +1854,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, * ones can be dropped even if they've * been dirtied. */ - (vma->vm_flags & VM_DROPPABLE))) { + folio_test_droppable(folio))) { dec_mm_counter(mm, MM_ANONPAGES); goto discard; } @@ -1866,7 +1868,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, * Unlike MADV_FREE mappings, VM_DROPPABLE ones * never get swap backed on failure to drop. */ - if (!(vma->vm_flags & VM_DROPPABLE)) + if (!folio_test_droppable(folio)) folio_set_swapbacked(folio); ret = false; page_vma_mapped_walk_done(&pvmw); diff --git a/mm/vmscan.c b/mm/vmscan.c index 2e34de9cd0d4..41340f2a12c7 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -4266,7 +4266,8 @@ static bool sort_folio(struct lruvec *lruvec, struct folio *folio, struct scan_c } /* dirty lazyfree */ - if (type == LRU_GEN_FILE && folio_test_anon(folio) && folio_test_dirty(folio)) { + if (type == LRU_GEN_FILE && folio_test_anon(folio) && + folio_test_dirty(folio) && !folio_test_droppable(folio)) { success = lru_gen_del_folio(lruvec, folio, true); VM_WARN_ON_ONCE_FOLIO(!success, folio); folio_set_swapbacked(folio);