On Fri, 2005-11-11 at 16:25 -0800, Andrew Morton wrote:
> Badari Pulavarty <[email protected]> wrote:
> >
> > +/*
> > + * Application wants to free up the pages and associated backing store.
> > + * This is effectively punching a hole into the middle of a file.
> > + *
> > + * NOTE: Currently, only shmfs/tmpfs is supported for this operation.
> > + * Other filesystems return -ENOSYS.
> > + */
> > +static long madvise_remove(struct vm_area_struct * vma,
> > + unsigned long start, unsigned long end)
> > +{
> > + struct address_space *mapping;
> > + loff_t offset, endoff;
> > +
> > + if (vma->vm_flags & (VM_LOCKED|VM_NONLINEAR|VM_HUGETLB))
> > + return -EINVAL;
> > +
> > + if (!vma->vm_file || !vma->vm_file->f_mapping
> > + || !vma->vm_file->f_mapping->host) {
> > + return -EINVAL;
> > + }
> > +
> > + mapping = vma->vm_file->f_mapping;
> > + if (mapping == &swapper_space) {
> > + return -EINVAL;
> > + }
> > +
> > + offset = (loff_t)(start - vma->vm_start)
> > + + (vma->vm_pgoff << PAGE_SHIFT);
> > + endoff = (loff_t)(end - vma->vm_start - 1)
> > + + (vma->vm_pgoff << PAGE_SHIFT);
> > + return vmtruncate_range(mapping->host, offset, endoff);
> > +}
> > +
>
> I'm suspecting you tested this on a 64-bit machine, yes? On 32-bit that
> vm_pgoff shift is going to overflow.
Yes. I have moved to all 64-bit (amd64, em64t, ppc64) machines. My bad.
>
> Fixes-thus-far below. Please rerun all tests on x86?
>
I will verify. Thanks.
> Why does madvise_remove() have an explicit check for swapper_space?
I really don't remember (I yanked code from some other kernel routine
vmtruncate()). If you think its unnecessary, I can take it out.
> In your testing, how are you determining that the code is successfully
> removing the correct number of pages, from the correct file offset?
I verified with test programs, added debug printk + looked through live
"crash" session + verified with UML testcases.
>
> diff -puN mm/madvise.c~madvise-remove-remove-pages-from-tmpfs-shm-backing-store-tidy mm/madvise.c
> --- devel/mm/madvise.c~madvise-remove-remove-pages-from-tmpfs-shm-backing-store-tidy 2005-11-11 16:12:43.000000000 -0800
> +++ devel-akpm/mm/madvise.c 2005-11-11 16:16:50.000000000 -0800
> @@ -147,8 +147,8 @@ static long madvise_dontneed(struct vm_a
> * NOTE: Currently, only shmfs/tmpfs is supported for this operation.
> * Other filesystems return -ENOSYS.
> */
> -static long madvise_remove(struct vm_area_struct * vma,
> - unsigned long start, unsigned long end)
> +static long madvise_remove(struct vm_area_struct *vma,
> + unsigned long start, unsigned long end)
> {
> struct address_space *mapping;
> loff_t offset, endoff;
> @@ -162,14 +162,13 @@ static long madvise_remove(struct vm_are
> }
>
> mapping = vma->vm_file->f_mapping;
> - if (mapping == &swapper_space) {
> + if (mapping == &swapper_space)
> return -EINVAL;
> - }
>
> offset = (loff_t)(start - vma->vm_start)
> - + (vma->vm_pgoff << PAGE_SHIFT);
> + + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
> endoff = (loff_t)(end - vma->vm_start - 1)
> - + (vma->vm_pgoff << PAGE_SHIFT);
> + + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
> return vmtruncate_range(mapping->host, offset, endoff);
> }
>
> diff -puN mm/memory.c~madvise-remove-remove-pages-from-tmpfs-shm-backing-store-tidy mm/memory.c
> --- devel/mm/memory.c~madvise-remove-remove-pages-from-tmpfs-shm-backing-store-tidy 2005-11-11 16:16:54.000000000 -0800
> +++ devel-akpm/mm/memory.c 2005-11-11 16:17:59.000000000 -0800
> @@ -1608,10 +1608,9 @@ out_big:
> out_busy:
> return -ETXTBSY;
> }
> -
> EXPORT_SYMBOL(vmtruncate);
>
> -int vmtruncate_range(struct inode * inode, loff_t offset, loff_t end)
> +int vmtruncate_range(struct inode *inode, loff_t offset, loff_t end)
> {
> struct address_space *mapping = inode->i_mapping;
>
> @@ -1634,7 +1633,6 @@ int vmtruncate_range(struct inode * inod
>
> return 0;
> }
> -
> EXPORT_SYMBOL(vmtruncate_range);
>
> /*
> _
>
>
-
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