kernel/include/linux/page-flags.h, branch linux-6.9.y

mm: turn folio_test_hugetlb into a PageType

2024-04-25T02:34:26Z

The current folio_test_hugetlb() can be fooled by a concurrent folio split into returning true for a folio which has never belonged to hugetlbfs. This can't happen if the caller holds a refcount on it, but we have a few places (memory-failure, compaction, procfs) which do not and should not take a speculative reference. Since hugetlb pages do not use individual page mapcounts (they are always fully mapped and use the entire_mapcount field to record the number of mappings), the PageType field is available now that page_mapcount() ignores the value in this field. In compaction and with CONFIG_DEBUG_VM enabled, the current implementation can result in an oops, as reported by Luis. This happens since 9c5ccf2db04b ("mm: remove HUGETLB_PAGE_DTOR") effectively added some VM_BUG_ON() checks in the PageHuge() testing path. [willy@infradead.org: update vmcoreinfo] Link: https://lkml.kernel.org/r/ZgGZUvsdhaT1Va-T@casper.infradead.org Link: https://lkml.kernel.org/r/20240321142448.1645400-6-willy@infradead.org Fixes: 9c5ccf2db04b ("mm: remove HUGETLB_PAGE_DTOR") Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: David Hildenbrand Acked-by: Vlastimil Babka Reported-by: Luis Chamberlain Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218227 Cc: Miaohe Lin Cc: Muchun Song Cc: Oscar Salvador Cc: Signed-off-by: Andrew Morton

mm: support page_mapcount() on page_has_type() pages

2024-04-25T02:34:26Z

Return 0 for pages which can't be mapped. This matches how page_mapped() works. It is more convenient for users to not have to filter out these pages. Link: https://lkml.kernel.org/r/20240321142448.1645400-5-willy@infradead.org Fixes: 9c5ccf2db04b ("mm: remove HUGETLB_PAGE_DTOR") Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: David Hildenbrand Acked-by: Vlastimil Babka Cc: Miaohe Lin Cc: Muchun Song Cc: Oscar Salvador Cc: Signed-off-by: Andrew Morton

mm: create FOLIO_FLAG_FALSE and FOLIO_TYPE_OPS macros

2024-04-25T02:34:25Z

Following the separation of FOLIO_FLAGS from PAGEFLAGS, separate FOLIO_FLAG_FALSE from PAGEFLAG_FALSE and FOLIO_TYPE_OPS from PAGE_TYPE_OPS. Link: https://lkml.kernel.org/r/20240321142448.1645400-3-willy@infradead.org Fixes: 9c5ccf2db04b ("mm: remove HUGETLB_PAGE_DTOR") Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: David Hildenbrand Acked-by: Vlastimil Babka Cc: Miaohe Lin Cc: Muchun Song Cc: Oscar Salvador Cc: Signed-off-by: Andrew Morton

mm: constify more page/folio tests

2024-03-06T21:04:18Z

Constify the flag tests that aren't automatically generated and the tests that look like flag tests but are more complicated. Link: https://lkml.kernel.org/r/20240227192337.757313-8-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: David Hildenbrand Signed-off-by: Andrew Morton

mm: constify testing page/folio flags

2024-03-06T21:04:18Z

Now that dump_page() takes a const argument, we can constify all the page flag tests. Link: https://lkml.kernel.org/r/20240227192337.757313-7-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: David Hildenbrand Signed-off-by: Andrew Morton

mm: remove PageYoung and PageIdle definitions

2024-03-06T21:04:17Z

All callers have been converted to use folios, so remove the various set/clear/test functions defined on pages. Link: https://lkml.kernel.org/r/20240227192337.757313-4-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: David Hildenbrand Signed-off-by: Andrew Morton

mm: remove PageWaiters, PageSetWaiters and PageClearWaiters

2024-03-06T21:04:17Z

All callers have been converted to use folios. This was the only user of PF_ONLY_HEAD, so remove that too. Link: https://lkml.kernel.org/r/20240227192337.757313-3-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: David Hildenbrand Signed-off-by: Andrew Morton

mm: separate out FOLIO_FLAGS from PAGEFLAGS

2024-03-06T21:04:17Z

Patch series "PageFlags cleanups". We have now successfully removed all of the uses of some of the PageFlags from the kernel, but there's nothing to stop somebody reintroducing them. By splitting out FOLIO_FLAGS from PAGEFLAGS, we can stop defining the old flags; and we do that in some of the later patches. After doing this, I realised that dump_page() was living dangerously; we could end up calling folio_test_foo() on a pointer which no longer pointed to a folio (as dump_page() is not necessarily called when the caller has a reference to the page). So I fixed that up. And then I realised that this was the key to making dump_page() take a const argument, which means we can constify the page flags testing, which means we can remove more cast-away-the-const bad code. And here's where I ended up. This patch (of 8): We've progressed far enough with the folio transition that some flags are now no longer checked on pages, but only on folios. To prevent new users appearing, prepare to only define the folio versions of the flag test/set/clear. Link: https://lkml.kernel.org/r/20240227192337.757313-1-willy@infradead.org Link: https://lkml.kernel.org/r/20240227192337.757313-2-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: David Hildenbrand Signed-off-by: Andrew Morton

mm: return void from folio_start_writeback() and related functions

2023-12-11T00:51:37Z

Nobody now checks the return value from any of these functions, so add an assertion at the beginning of the function and return void. Link: https://lkml.kernel.org/r/20231108204605.745109-5-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: Josef Bacik Cc: David Howells Cc: Steve French Signed-off-by: Andrew Morton

mm: remove test_set_page_writeback()

2023-12-11T00:51:36Z

Patch series "Make folio_start_writeback return void". Most of the folio flag-setting functions return void. folio_start_writeback is gratuitously different; the only two filesystems that do anything with the return value emit debug messages if it's already set, and we can (and should) do that internally without bothering the filesystem to do it. This patch (of 4): There are no more callers of this wrapper. Link: https://lkml.kernel.org/r/20231108204605.745109-1-willy@infradead.org Link: https://lkml.kernel.org/r/20231108204605.745109-2-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) Cc: David Howells Cc: Steve French Signed-off-by: Andrew Morton