kernel/include/linux/page-flags.h, branch linux-6.11.y

mm: read page_type using READ_ONCE

2024-07-04T02:30:20Z

KCSAN complains about possible data races: while we check for a page_type -- for example for sanity checks -- we might concurrently modify the mapcount that overlays page_type. Let's use READ_ONCE to avoid load tearing (shouldn't make a difference) and to make KCSAN happy. Likely, we might also want to use WRITE_ONCE for the writer side of page_type, if KCSAN ever complains about that. But we'll not mess with that for now. Note: nothing should really be broken besides wrong KCSAN complaints. The sanity check that triggers this was added in commit 68f0320824fa ("mm/rmap: convert folio_add_file_rmap_range() into folio_add_file_rmap_[pte|ptes|pmd]()"). Even before that similar races likely where possible, ever since we added page_type in commit 6e292b9be7f4 ("mm: split page_type out from _mapcount"). Link: https://lkml.kernel.org/r/20240531125616.2850153-1-david@redhat.com Signed-off-by: David Hildenbrand Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-lkp/202405281431.c46a3be9-lkp@intel.com Reviewed-by: Oscar Salvador Reviewed-by: Miaohe Lin Cc: Matthew Wilcox Signed-off-by: Andrew Morton

mm/memory_hotplug: skip adjust_managed_page_count() for PageOffline() pages when offlining

2024-07-04T02:30:18Z

We currently have a hack for virtio-mem in place to handle memory offlining with PageOffline pages for which we already adjusted the managed page count. Let's enlighten memory offlining code so we can get rid of that hack, and document the situation. Link: https://lkml.kernel.org/r/20240607090939.89524-4-david@redhat.com Signed-off-by: David Hildenbrand Acked-by: Oscar Salvador Cc: Alexander Potapenko Cc: Dexuan Cui Cc: Dmitry Vyukov Cc: Eugenio Pérez Cc: Haiyang Zhang Cc: Jason Wang Cc: Juergen Gross Cc: "K. Y. Srinivasan" Cc: Marco Elver Cc: Michael S. Tsirkin Cc: Mike Rapoport (IBM) Cc: Oleksandr Tyshchenko Cc: Stefano Stabellini Cc: Wei Liu Cc: Xuan Zhuo Signed-off-by: Andrew Morton

mm/memory_hotplug: initialize memmap of !ZONE_DEVICE with PageOffline() instead of PageReserved()

2024-07-04T02:30:18Z

We currently initialize the memmap such that PG_reserved is set and the refcount of the page is 1. In virtio-mem code, we have to manually clear that PG_reserved flag to make memory offlining with partially hotplugged memory blocks possible: has_unmovable_pages() would otherwise bail out on such pages. We want to avoid PG_reserved where possible and move to typed pages instead. Further, we want to further enlighten memory offlining code about PG_offline: offline pages in an online memory section. One example is handling managed page count adjustments in a cleaner way during memory offlining. So let's initialize the pages with PG_offline instead of PG_reserved. generic_online_page()->__free_pages_core() will now clear that flag before handing that memory to the buddy. Note that the page refcount is still 1 and would forbid offlining of such memory except when special care is take during GOING_OFFLINE as currently only implemented by virtio-mem. With this change, we can now get non-PageReserved() pages in the XEN balloon list. From what I can tell, that can already happen via decrease_reservation(), so that should be fine. HV-balloon should not really observe a change: partial online memory blocks still cannot get surprise-offlined, because the refcount of these PageOffline() pages is 1. Update virtio-mem, HV-balloon and XEN-balloon code to be aware that hotplugged pages are now PageOffline() instead of PageReserved() before they are handed over to the buddy. We'll leave the ZONE_DEVICE case alone for now. Note that self-hosted vmemmap pages will no longer be marked as reserved. This matches ordinary vmemmap pages allocated from the buddy during memory hotplug. Now, really only vmemmap pages allocated from memblock during early boot will be marked reserved. Existing PageReserved() checks seem to be handling all relevant cases correctly even after this change. Link: https://lkml.kernel.org/r/20240607090939.89524-3-david@redhat.com Signed-off-by: David Hildenbrand Acked-by: Oscar Salvador [generic memory-hotplug bits] Cc: Alexander Potapenko Cc: Dexuan Cui Cc: Dmitry Vyukov Cc: Eugenio Pérez Cc: Haiyang Zhang Cc: Jason Wang Cc: Juergen Gross Cc: "K. Y. Srinivasan" Cc: Marco Elver Cc: Michael S. Tsirkin Cc: Mike Rapoport (IBM) Cc: Oleksandr Tyshchenko Cc: Stefano Stabellini Cc: Wei Liu Cc: Xuan Zhuo Signed-off-by: Andrew Morton

mm/zsmalloc: use a proper page type

2024-07-04T02:30:16Z

Let's clean it up: use a proper page type and store our data (offset into a page) in the lower 16 bit as documented. We won't be able to support 256 KiB base pages, which is acceptable. Teach Kconfig to handle that cleanly using a new CONFIG_HAVE_ZSMALLOC. Based on this, we should do a proper "struct zsdesc" conversion, as proposed in [1]. This removes the last _mapcount/page_type offender. [1] https://lore.kernel.org/all/20231130101242.2590384-1-42.hyeyoo@gmail.com/ Link: https://lkml.kernel.org/r/20240529111904.2069608-4-david@redhat.com Signed-off-by: David Hildenbrand Tested-by: Sergey Senozhatsky [zram/zsmalloc workloads] Reviewed-by: Sergey Senozhatsky Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com> Cc: Matthew Wilcox (Oracle) Cc: Mike Rapoport (IBM) Cc: Minchan Kim Signed-off-by: Andrew Morton

mm: allow reuse of the lower 16 bit of the page type with an actual type

2024-07-04T02:30:16Z

As long as the owner sets a page type first, we can allow reuse of the lower 16 bit: sufficient to store an offset into a 64 KiB page, which is the maximum base page size in *common* configurations (ignoring the 256 KiB variant). Restrict it to the head page. We'll use that for zsmalloc next, to set a proper type while still reusing that field to store information (offset into a base page) that cannot go elsewhere for now. Let's reserve the lower 16 bit for that purpose and for catching mapcount underflows, and let's reduce PAGE_TYPE_BASE to a single bit. Note that we will still have to overflow the mapcount quite a lot until we would actually indicate a valid page type. Start handing out the type bits from highest to lowest, to make it clearer how many bits for types we have left. Out of 15 bit we can use for types, we currently use 6. If we run out of bits before we have better typing (e.g., memdesc), we can always investigate storing a value instead [1]. [1] https://lore.kernel.org/all/00ba1dff-7c05-46e8-b0d9-a78ac1cfc198@redhat.com/ [akpm@linux-foundation.org: fix PG_hugetlb typo, per David] Link: https://lkml.kernel.org/r/20240529111904.2069608-3-david@redhat.com Signed-off-by: David Hildenbrand Tested-by: Sergey Senozhatsky [zram/zsmalloc workloads] Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com> Cc: Matthew Wilcox (Oracle) Cc: Mike Rapoport (IBM) Cc: Minchan Kim Signed-off-by: Andrew Morton

mm/memory-failure: move some function declarations into internal.h

2024-07-04T02:30:11Z

There are some functions only used inside mm. Move them into internal.h. No functional change intended. Link: https://lkml.kernel.org/r/20240612071835.157004-11-linmiaohe@huawei.com Signed-off-by: Miaohe Lin Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202405251049.hxjwX7zO-lkp@intel.com/ Cc: Borislav Petkov (AMD) Cc: David Hildenbrand Cc: Naoya Horiguchi Cc: Tony Luck Signed-off-by: Andrew Morton

mm: remove page_mapping()

2024-07-04T02:29:59Z

All callers are now converted, delete this compatibility wrapper. Also fix up some comments which referred to page_mapping. Link: https://lkml.kernel.org/r/20240423225552.4113447-7-willy@infradead.org Link: https://lkml.kernel.org/r/20240524181813.698813-1-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: David Hildenbrand Cc: Eric Biggers Cc: Sidhartha Kumar Signed-off-by: Andrew Morton

mm: convert page type macros to enum

2024-06-25T03:52:10Z

Changing PG_slab from a page flag to a page type in commit 46df8e73a4a3 ("mm: free up PG_slab") in has the unintended consequence of removing the PG_slab constant from kernel debuginfo. The commit does add the value to the vmcoreinfo note, which allows debuggers to find the value without hardcoding it. However it's most flexible to continue representing the constant with an enum. To that end, convert the page type fields into an enum. Debuggers will now be able to detect that PG_slab's type has changed from enum pageflags to enum pagetype. Link: https://lkml.kernel.org/r/20240607202954.1198180-1-stephen.s.brennan@oracle.com Fixes: 46df8e73a4a3 ("mm: free up PG_slab") Signed-off-by: Stephen Brennan Acked-by: Vlastimil Babka Cc: David Hildenbrand Cc: Hao Ge Cc: Matthew Wilcox (Oracle) Cc: Omar Sandoval Cc: Vishal Moola (Oracle) Signed-off-by: Andrew Morton

mm: remove PageReferenced

2024-05-06T00:53:50Z

All callers now use folio_*_referenced() so we can remove the PageReferenced family of functions. Link: https://lkml.kernel.org/r/20240424191914.361554-8-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) Signed-off-by: Andrew Morton

mm/page-flags: make PageUptodate return bool

2024-05-06T00:53:43Z

Make PageUptodate return bool to align the return values of folio_test_uptodate function Link: https://lkml.kernel.org/r/20240422032725.41452-1-gehao@kylinos.cn Signed-off-by: Hao Ge Cc: David Hildenbrand Cc: Josef Bacik Cc: Matthew Wilcox (Oracle) Cc: Ruihan Li Cc: Vishal Moola (Oracle) Signed-off-by: Andrew Morton