RFP prot support: also set VM_NONLINEAR on nonuniform VMAs From: Paolo 'Blaisorblade' Giarrusso To simplify the VM code, and to reflect expected application usage, we decide to also set VM_NONLINEAR when setting VM_MANYPROTS. Otherwise, we'd have to possibly save nonlinear PTEs even on paths which cope with linear VMAs. It's possible, but intrusive (it's done in one of the next patches). Obviously, this has a performance cost, since we potentially have to handle a linear VMA with nonlinear handling code. But I didn't know of any application which might have this usage. XXX: update: glibc wants to replace mprotect() with linear VM_MANYPROTS areas, to handle guard pages and data mappings of shared objects. Signed-off-by: Paolo 'Blaisorblade' Giarrusso --- mm/fremap.c | 27 ++++++++++++++------------- 1 files changed, 14 insertions(+), 13 deletions(-) diff --git a/mm/fremap.c b/mm/fremap.c index b1db410..3438caf 100644 --- a/mm/fremap.c +++ b/mm/fremap.c @@ -213,8 +213,9 @@ retry: if (!vma->vm_private_data || (vma->vm_flags & VM_NONLINEAR)) { /* Must set VM_NONLINEAR before any pages are populated. */ - if (pgoff != linear_page_index(vma, start) && - !(vma->vm_flags & VM_NONLINEAR)) { + if (!(vma->vm_flags & VM_NONLINEAR) && + (pgoff != linear_page_index(vma, start) || + pgprot_val(pgprot) != pgprot_val(vma->vm_page_prot))) { if (!(vma->vm_flags & VM_SHARED)) goto out_unlock; if (!has_write_lock) { @@ -231,19 +232,19 @@ retry: vma_nonlinear_insert(vma, &mapping->i_mmap_nonlinear); flush_dcache_mmap_unlock(mapping); spin_unlock(&mapping->i_mmap_lock); - } - if (pgprot_val(pgprot) != pgprot_val(vma->vm_page_prot) && - !(vma->vm_flags & VM_MANYPROTS)) { - if (!(vma->vm_flags & VM_SHARED)) - goto out_unlock; - if (!has_write_lock) { - up_read(&mm->mmap_sem); - down_write(&mm->mmap_sem); - has_write_lock = 1; - goto retry; + if (!(vma->vm_flags & VM_MANYPROTS) && + pgprot_val(pgprot) != pgprot_val(vma->vm_page_prot)) { + if (!(vma->vm_flags & VM_SHARED)) + goto out_unlock; + if (!has_write_lock) { + up_read(&mm->mmap_sem); + down_write(&mm->mmap_sem); + has_write_lock = 1; + goto retry; + } + vma->vm_flags |= VM_MANYPROTS; } - vma->vm_flags |= VM_MANYPROTS; } err = vma->vm_ops->populate(vma, start, size, pgprot, pgoff,