Messages in this thread Patch in this message | | | From | Alex Thorlton <> | Subject | [PATCH 1/3] Revert "thp: make MADV_HUGEPAGE check for mm->def_flags" | Date | Tue, 25 Feb 2014 14:54:04 -0600 |
| |
This reverts commit 8e72033f2a489b6c98c4e3c7cc281b1afd6cb85c, and adds in code to fix up any issues caused by the revert.
The revert is necessary because hugepage_madvise would return -EINVAL when VM_NOHUGEPAGE is set, which will break subsequent chunks of this patch set.
Here's a snip of an e-mail from Gerald detailing the original purpose of this code, and providing justification for the revert:
<snip> The intent of 8e72033f2a48 was to guard against any future programming errors that may result in an madvice(MADV_HUGEPAGE) on guest mappings, which would crash the kernel.
Martin suggested adding the bit to arch/s390/mm/pgtable.c, if 8e72033f2a48 was to be reverted, because that check will also prevent a kernel crash in the case described above, it will now send a SIGSEGV instead.
This would now also allow to do the madvise on other parts, if needed, so it is a more flexible approach. One could also say that it would have been better to do it this way right from the beginning... </snip>
Signed-off-by: Alex Thorlton <athorlton@sgi.com> Suggested-by: Oleg Nesterov <oleg@redhat.com> Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Rik van Riel <riel@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: linux390@de.ibm.com Cc: linux-s390@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org Cc: linux-api@vger.kernel.org
--- arch/s390/mm/pgtable.c | 3 +++ mm/huge_memory.c | 4 ---- 2 files changed, 3 insertions(+), 4 deletions(-)
diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c index 3584ed9..a87cdb4 100644 --- a/arch/s390/mm/pgtable.c +++ b/arch/s390/mm/pgtable.c @@ -504,6 +504,9 @@ static int gmap_connect_pgtable(unsigned long address, unsigned long segment, if (!pmd_present(*pmd) && __pte_alloc(mm, vma, pmd, vmaddr)) return -ENOMEM; + /* large pmds cannot yet be handled */ + if (pmd_large(*pmd)) + return -EFAULT; /* pmd now points to a valid segment table entry. */ rmap = kmalloc(sizeof(*rmap), GFP_KERNEL|__GFP_REPEAT); if (!rmap) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 82166bf..a4310a5 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1968,8 +1968,6 @@ out: int hugepage_madvise(struct vm_area_struct *vma, unsigned long *vm_flags, int advice) { - struct mm_struct *mm = vma->vm_mm; - switch (advice) { case MADV_HUGEPAGE: /* @@ -1977,8 +1975,6 @@ int hugepage_madvise(struct vm_area_struct *vma, */ if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP)) return -EINVAL; - if (mm->def_flags & VM_NOHUGEPAGE) - return -EINVAL; *vm_flags &= ~VM_NOHUGEPAGE; *vm_flags |= VM_HUGEPAGE; /* -- 1.7.12.4
| |