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authorZach O'Keefe <zokeefe@google.com>2023-09-25 13:01:10 -0700
committerAndrew Morton <akpm@linux-foundation.org>2023-10-18 14:34:18 -0700
commit7a81751fcdeb833acc858e59082688e3020bfe12 (patch)
tree00447a9c624384c6f7e9cd5473c7b3c435476527 /mm
parentc0dddb7aa5f85e6150a1e3230e01d5ba286eded9 (diff)
mm/thp: fix "mm: thp: kill __transhuge_page_enabled()"
The 6.0 commits: commit 9fec51689ff6 ("mm: thp: kill transparent_hugepage_active()") commit 7da4e2cb8b1f ("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: 7da4e2cb8b1f ("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>
Diffstat (limited to 'mm')
-rw-r--r--mm/huge_memory.c20
1 files changed, 13 insertions, 7 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 51a66eb48938..c9cbcbf6697e 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -100,11 +100,11 @@ bool hugepage_vma_check(struct vm_area_struct *vma, unsigned long vm_flags,
return in_pf;
/*
- * Special VMA and hugetlb VMA.
+ * khugepaged special VMA and hugetlb VMA.
* Must be checked after dax since some dax mappings may have
* VM_MIXEDMAP set.
*/
- if (vm_flags & VM_NO_KHUGEPAGED)
+ if (!in_pf && !smaps && (vm_flags & VM_NO_KHUGEPAGED))
return false;
/*
@@ -132,12 +132,18 @@ bool hugepage_vma_check(struct vm_area_struct *vma, unsigned long vm_flags,
!hugepage_flags_always())))
return false;
- /* Only regular file is valid */
- if (!in_pf && file_thp_enabled(vma))
- return true;
-
- if (!vma_is_anonymous(vma))
+ if (!vma_is_anonymous(vma)) {
+ /*
+ * Trust that ->huge_fault() handlers know what they are doing
+ * in fault path.
+ */
+ if (((in_pf || smaps)) && vma->vm_ops->huge_fault)
+ return true;
+ /* Only regular file is valid in collapse path */
+ if (((!in_pf || smaps)) && file_thp_enabled(vma))
+ return true;
return false;
+ }
if (vma_is_temporary_stack(vma))
return false;