Hi Kirill, Due to broken PAGE_FILE on arc, I was giving this emulation patch a try and it seems we need a minor fix to this patch. I know this is not slated for merge soon, but u can add the fix nevertheless and my Tested-by: Problem showed up with Ingo Korb's remap-demo.c test case from [1] [1] https://lkml.org/lkml/2014/7/14/335 On Tuesday 06 May 2014 08:07 PM, Kirill A. Shutemov wrote: > remap_file_pages(2) was invented to be able efficiently map parts of > huge file into limited 32-bit virtual address space such as in database > workloads. > > Nonlinear mappings are pain to support and it seems there's no > legitimate use-cases nowadays since 64-bit systems are widely available. > > Let's drop it and get rid of all these special-cased code. > > The patch replaces the syscall with emulation which creates new VMA on > each remap. > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > --- .... > -} > diff --git a/mm/mmap.c b/mm/mmap.c > index b1202cf81f4b..4106fc833f56 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -2579,6 +2579,74 @@ SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len) > return vm_munmap(addr, len); > } > > + > +/* > + * Emulation of deprecated remap_file_pages() syscall. > + */ > +SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size, > + unsigned long, prot, unsigned long, pgoff, unsigned long, flags) > +{ > + > + struct mm_struct *mm = current->mm; > + struct vm_area_struct *vma; > + unsigned long populate; > + int ret = -EINVAL; > + > + printk_once(KERN_WARNING "%s (%d) calls remap_file_pages(2) which is " > + "deprecated and no longer supported by kernel in " > + "an efficient way.\n" > + "Note that emulated remap_file_pages(2) can " > + "potentially create a lot of mappings. " > + "Consider increasing vm.max_map_count.\n", > + current->comm, current->pid); > + > + if (prot) > + return ret; > + start = start & PAGE_MASK; > + size = size & PAGE_MASK; > + > + if (start + size <= start) > + return ret; > + > + /* Does pgoff wrap? */ > + if (pgoff + (size >> PAGE_SHIFT) < pgoff) > + return ret; > + > + down_write(&mm->mmap_sem); > + vma = find_vma(mm, start); > + > + if (!vma || !(vma->vm_flags & VM_SHARED)) > + goto out; > + > + if (start < vma->vm_start || start + size > vma->vm_end) > + goto out; > + > + if (pgoff == linear_page_index(vma, start)) { > + ret = 0; > + goto out; > + } > + > + prot |= vma->vm_flags & VM_READ ? PROT_READ : 0; > + prot |= vma->vm_flags & VM_WRITE ? PROT_WRITE : 0; > + prot |= vma->vm_flags & VM_EXEC ? PROT_EXEC : 0; > + > + flags &= MAP_POPULATE; > + flags |= MAP_SHARED | MAP_FIXED; > + if (vma->vm_flags & VM_LOCKED) { > + flags |= MAP_LOCKED; > + /* drop PG_Mlocked flag for over-mapped range */ > + munlock_vma_pages_range(vma, start, start + size); > + } > + > + ret = do_mmap_pgoff(vma->vm_file, start, size, > + prot, flags, pgoff, &populate); > + if (populate) > + mm_populate(ret, populate); > +out: > + up_write(&mm->mmap_sem); On success needs to return 0, not mapped addr. if (!IS_ERR_VALUE(ret)) ret = 0; > + return ret; > +} > + Thx, -Vineet -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>