Messages in this thread | | | Date | Wed, 16 Aug 2023 11:45:53 +0200 | From | Michał Mirosław <> | Subject | Re: [PATCH v30 2/6] fs/proc/task_mmu: Implement IOCTL to get and optionally clear info about PTEs |
| |
On Wed, Aug 16, 2023 at 11:59:21AM +0500, Muhammad Usama Anjum wrote: > The PAGEMAP_SCAN IOCTL on the pagemap file can be used to get or optionally > clear the info about page table entries. [...] > --- a/fs/proc/task_mmu.c > +++ b/fs/proc/task_mmu.c [...] > +static long do_pagemap_scan(struct mm_struct *mm, unsigned long uarg) > +{ [...] > + for (walk_start = p.arg.start; walk_start < p.arg.end; > + walk_start = p.arg.walk_end) { > + long n_out; > + > + if (fatal_signal_pending(current)) { > + ret = -EINTR; > + break; > + } > + > + ret = mmap_read_lock_killable(mm); > + if (ret) > + break; > + ret = walk_page_range(mm, walk_start, p.arg.end, > + &pagemap_scan_ops, &p); > + mmap_read_unlock(mm); > + > + n_out = pagemap_scan_flush_buffer(&p); > + if (n_out < 0) > + ret = n_out; > + else > + n_ranges_out += n_out; > + > + p.arg.walk_end = p.walk_end_addr ? p.walk_end_addr : p.arg.end;
I think p.walk_end_addr can be removed and replaced by `p.arg.walk_end` directly in the walk functions. If we don't set walk_end_addr we'll also return 0 so the check below will match. Might be good to add this as a comment.
> + if (ret != -ENOSPC) > + break; > + > + if (p.arg.vec_len == 0 || p.found_pages == p.arg.max_pages) > + break; > + } > + > + /* ENOSPC signifies early stop (buffer full) from the walk. */ > + if (!ret || ret == -ENOSPC) > + ret = n_ranges_out; > + > + p.arg.walk_end = p.arg.walk_end ? p.arg.walk_end : walk_start;
When the walk is finished, with ret == 0, the walk_start will point to the beginning, not the end of the range. So:
if (!walk_end) walk_end = p.arg.end;
Other than that, the patch looks complete now. Thanks for all your work!
Best Regards Michał Mirosław
| |