On 02/08/2024 16:55, David Hildenbrand wrote: > Let's remove yet another follow_page() user. Note that we have to do the > split without holding the PTL, after folio_walk_end(). We don't care > about losing the secretmem check in follow_page(). Hi David, Our (arm64) CI is showing a regression in split_huge_page_test from mm selftests from next-20240805 onwards. Navigating around a couple of other lurking bugs, I was able to bisect to this change (which smells about right). Newly failing test: # # ------------------------------ # # running ./split_huge_page_test # # ------------------------------ # # TAP version 13 # # 1..12 # # Bail out! Still AnonHugePages not split # # # Planned tests != run tests (12 != 0) # # # Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0 # # [FAIL] # not ok 52 split_huge_page_test # exit=1 It's trying to split some pmd-mapped THPs then checking and finding that they are not split. The split is requested via /sys/kernel/debug/split_huge_pages, which I believe ends up in this function you are modifying here. Although I'll admit that looking at the change, there is nothing obviously wrong! Any ideas? bisect log: # bad: [1e391b34f6aa043c7afa40a2103163a0ef06d179] Add linux-next specific files for 20240806 git bisect bad 1e391b34f6aa043c7afa40a2103163a0ef06d179 # good: [de9c2c66ad8e787abec7c9d7eff4f8c3cdd28aed] Linux 6.11-rc2 git bisect good de9c2c66ad8e787abec7c9d7eff4f8c3cdd28aed # bad: [01c2d56f2c52e8af01dfd91af1fe9affc76c4c9e] Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git git bisect bad 01c2d56f2c52e8af01dfd91af1fe9affc76c4c9e # bad: [01c2d56f2c52e8af01dfd91af1fe9affc76c4c9e] Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git git bisect bad 01c2d56f2c52e8af01dfd91af1fe9affc76c4c9e # bad: [3610638e967f32f02c56c7cc8f7d6a815972f8c2] Merge branch 'for-linux-next' of git://git.kernel.org/pub/scm/linux/kernel/git/sudeep.holla/linux.git git bisect bad 3610638e967f32f02c56c7cc8f7d6a815972f8c2 # bad: [3610638e967f32f02c56c7cc8f7d6a815972f8c2] Merge branch 'for-linux-next' of git://git.kernel.org/pub/scm/linux/kernel/git/sudeep.holla/linux.git git bisect bad 3610638e967f32f02c56c7cc8f7d6a815972f8c2 # bad: [d35ef6c9d106eedff36908c21699e1b7f3e55584] Merge branch 'clang-format' of https://github.com/ojeda/linux.git git bisect bad d35ef6c9d106eedff36908c21699e1b7f3e55584 # good: [e1a15959d75c9ba4b45e07e37bcf843c85750010] Merge branch 'for-linux-next-fixes' of https://gitlab.freedesktop.org/drm/misc/kernel.git git bisect good e1a15959d75c9ba4b45e07e37bcf843c85750010 # good: [6d66cb9bdeceb769ce62591f56580ebe80f6267a] mm: swap: add a adaptive full cluster cache reclaim git bisect good 6d66cb9bdeceb769ce62591f56580ebe80f6267a # bad: [2b820b576dfc4aa9b65f18b68f468cb5b38ece84] mm: optimization on page allocation when CMA enabled git bisect bad 2b820b576dfc4aa9b65f18b68f468cb5b38ece84 # bad: [ab70279848c8623027791799492a3f6e7c38a9b2] MIPS: sgi-ip27: drop HAVE_ARCH_NODEDATA_EXTENSION git bisect bad ab70279848c8623027791799492a3f6e7c38a9b2 # bad: [539bc09ff00b29eb60f3dc8ed2d82ad2050a582d] mm/huge_memory: convert split_huge_pages_pid() from follow_page() to folio_walk git bisect bad 539bc09ff00b29eb60f3dc8ed2d82ad2050a582d # good: [1a37544d0e35340ce740d377d7d6c746a84e2aae] include/linux/mmzone.h: clean up watermark accessors git bisect good 1a37544d0e35340ce740d377d7d6c746a84e2aae # good: [22adafb60d6e1a607a3d99da90927ddd7df928ad] mm/migrate: convert do_pages_stat_array() from follow_page() to folio_walk git bisect good 22adafb60d6e1a607a3d99da90927ddd7df928ad # good: [57e1ccf54dba4dda6d6f0264b76e2b86eec3d401] mm/ksm: convert get_mergeable_page() from follow_page() to folio_walk git bisect good 57e1ccf54dba4dda6d6f0264b76e2b86eec3d401 # good: [285aa1a963f310530351b0e4a2e64bc4b806e518] mm/ksm: convert scan_get_next_rmap_item() from follow_page() to folio_walk git bisect good 285aa1a963f310530351b0e4a2e64bc4b806e518 # first bad commit: [539bc09ff00b29eb60f3dc8ed2d82ad2050a582d] mm/huge_memory: convert split_huge_pages_pid() from follow_page() to folio_walk Thanks, Ryan > > Signed-off-by: David Hildenbrand <david@xxxxxxxxxx> > --- > mm/huge_memory.c | 18 +++++++++++------- > 1 file changed, 11 insertions(+), 7 deletions(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 0167dc27e365..697fcf89f975 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -40,6 +40,7 @@ > #include <linux/memory-tiers.h> > #include <linux/compat.h> > #include <linux/pgalloc_tag.h> > +#include <linux/pagewalk.h> > > #include <asm/tlb.h> > #include <asm/pgalloc.h> > @@ -3507,7 +3508,7 @@ static int split_huge_pages_pid(int pid, unsigned long vaddr_start, > */ > for (addr = vaddr_start; addr < vaddr_end; addr += PAGE_SIZE) { > struct vm_area_struct *vma = vma_lookup(mm, addr); > - struct page *page; > + struct folio_walk fw; > struct folio *folio; > > if (!vma) > @@ -3519,13 +3520,10 @@ static int split_huge_pages_pid(int pid, unsigned long vaddr_start, > continue; > } > > - /* FOLL_DUMP to ignore special (like zero) pages */ > - page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP); > - > - if (IS_ERR_OR_NULL(page)) > + folio = folio_walk_start(&fw, vma, addr, 0); > + if (!folio) > continue; > > - folio = page_folio(page); > if (!is_transparent_hugepage(folio)) > goto next; > > @@ -3544,13 +3542,19 @@ static int split_huge_pages_pid(int pid, unsigned long vaddr_start, > > if (!folio_trylock(folio)) > goto next; > + folio_get(folio); > + folio_walk_end(&fw, vma); > > if (!split_folio_to_order(folio, new_order)) > split++; > > folio_unlock(folio); > -next: > folio_put(folio); > + > + cond_resched(); > + continue; > +next: > + folio_walk_end(&fw, vma); > cond_resched(); > } > mmap_read_unlock(mm);
