mm/thp: fix "mm: thp: kill __transhuge_page_enabled()"
The 6.0 commits: commit9fec51689f
("mm: thp: kill transparent_hugepage_active()") commit7da4e2cb8b
("mm: thp: kill __transhuge_page_enabled()") merged "can we have THPs in this VMA?" logic that was previously done separately by fault-path, khugepaged, and smaps "THPeligible" checks. During the process, the semantics of the fault path check changed in two ways: 1) A VM_NO_KHUGEPAGED check was introduced (also added to smaps path). 2) We no longer checked if non-anonymous memory had a vm_ops->huge_fault handler that could satisfy the fault. Previously, this check had been done in create_huge_pud() and create_huge_pmd() routines, but after the changes, we never reach those routines. During the review of the above commits, it was determined that in-tree users weren't affected by the change; most notably, since the only relevant user (in terms of THP) of VM_MIXEDMAP or ->huge_fault is DAX, which is explicitly approved early in approval logic. However, this was a bad assumption to make as it assumes the only reason to support ->huge_fault was for DAX (which is not true in general). Remove the VM_NO_KHUGEPAGED check when not in collapse path and give any ->huge_fault handler a chance to handle the fault. Note that we don't validate the file mode or mapping alignment, which is consistent with the behavior before the aforementioned commits. Link: https://lkml.kernel.org/r/20230925200110.1979606-1-zokeefe@google.com Fixes:7da4e2cb8b
("mm: thp: kill __transhuge_page_enabled()") Reported-by: Saurabh Singh Sengar <ssengar@microsoft.com> Signed-off-by: Zach O'Keefe <zokeefe@google.com> Cc: Yang Shi <shy828301@gmail.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: David Hildenbrand <david@redhat.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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@ -100,11 +100,11 @@ bool hugepage_vma_check(struct vm_area_struct *vma, unsigned long vm_flags,
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return in_pf;
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/*
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* Special VMA and hugetlb VMA.
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* khugepaged special VMA and hugetlb VMA.
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* Must be checked after dax since some dax mappings may have
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* VM_MIXEDMAP set.
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*/
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if (vm_flags & VM_NO_KHUGEPAGED)
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if (!in_pf && !smaps && (vm_flags & VM_NO_KHUGEPAGED))
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return false;
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/*
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@ -132,12 +132,18 @@ bool hugepage_vma_check(struct vm_area_struct *vma, unsigned long vm_flags,
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!hugepage_flags_always())))
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return false;
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/* Only regular file is valid */
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if (!in_pf && file_thp_enabled(vma))
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if (!vma_is_anonymous(vma)) {
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/*
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* Trust that ->huge_fault() handlers know what they are doing
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* in fault path.
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*/
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if (((in_pf || smaps)) && vma->vm_ops->huge_fault)
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return true;
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/* Only regular file is valid in collapse path */
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if (((!in_pf || smaps)) && file_thp_enabled(vma))
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return true;
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if (!vma_is_anonymous(vma))
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return false;
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}
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if (vma_is_temporary_stack(vma))
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return false;
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