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uprobe: use original page when all uprobes are removed

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Currently, uprobe swaps the target page with a anonymous page in both
install_breakpoint() and remove_breakpoint().  When all uprobes on a page
are removed, the given mm is still using an anonymous page (not the
original page).

This patch allows uprobe to use original page when possible (all uprobes
on the page are already removed, and the original page is in page cache
and uptodate).

As suggested by Oleg, we unmap the old_page and let the original page
fault in.

Link: http://lkml.kernel.org/r/20190815164525.1848545-3-songliubraving@fb.com
Signed-off-by: Song Liu <songliubraving@fb.com>
Suggested-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Song Liu 2019-09-23 15:38:22 -07:00 committed by Linus Torvalds
parent 010c164a5f
commit fb4fb04ff4
1 changed files with 51 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

66
kernel/events/uprobes.c
View File

@ -143,10 +143,12 @@ static loff_t vaddr_to_offset(struct vm_area_struct *vma, unsigned long vaddr)
*
* @vma: vma that holds the pte pointing to page
* @addr: address the old @page is mapped at
* @page: the cowed page we are replacing by kpage
* @kpage: the modified page we replace page by
* @old_page: the page we are replacing by new_page
* @new_page: the modified page we replace page by
*
* Returns 0 on success, -EFAULT on failure.
* If @new_page is NULL, only unmap @old_page.
*
* Returns 0 on success, negative error code otherwise.
*/
static int __replace_page(struct vm_area_struct *vma, unsigned long addr,
struct page *old_page, struct page *new_page)
@ -166,10 +168,12 @@ static int __replace_page(struct vm_area_struct *vma, unsigned long addr,
VM_BUG_ON_PAGE(PageTransHuge(old_page), old_page);
err = mem_cgroup_try_charge(new_page, vma->vm_mm, GFP_KERNEL, &memcg,
false);
if (err)
return err;
if (new_page) {
err = mem_cgroup_try_charge(new_page, vma->vm_mm, GFP_KERNEL,
&memcg, false);
if (err)
return err;
}
/* For try_to_free_swap() and munlock_vma_page() below */
lock_page(old_page);
@ -177,15 +181,20 @@ static int __replace_page(struct vm_area_struct *vma, unsigned long addr,
mmu_notifier_invalidate_range_start(&range);
err = -EAGAIN;
if (!page_vma_mapped_walk(&pvmw)) {
mem_cgroup_cancel_charge(new_page, memcg, false);
if (new_page)
mem_cgroup_cancel_charge(new_page, memcg, false);
goto unlock;
}
VM_BUG_ON_PAGE(addr != pvmw.address, old_page);
get_page(new_page);
page_add_new_anon_rmap(new_page, vma, addr, false);
mem_cgroup_commit_charge(new_page, memcg, false, false);
lru_cache_add_active_or_unevictable(new_page, vma);
if (new_page) {
get_page(new_page);
page_add_new_anon_rmap(new_page, vma, addr, false);
mem_cgroup_commit_charge(new_page, memcg, false, false);
lru_cache_add_active_or_unevictable(new_page, vma);
} else
/* no new page, just dec_mm_counter for old_page */
dec_mm_counter(mm, MM_ANONPAGES);
if (!PageAnon(old_page)) {
dec_mm_counter(mm, mm_counter_file(old_page));
@ -194,8 +203,9 @@ static int __replace_page(struct vm_area_struct *vma, unsigned long addr,
flush_cache_page(vma, addr, pte_pfn(*pvmw.pte));
ptep_clear_flush_notify(vma, addr, pvmw.pte);
set_pte_at_notify(mm, addr, pvmw.pte,
mk_pte(new_page, vma->vm_page_prot));
if (new_page)
set_pte_at_notify(mm, addr, pvmw.pte,
mk_pte(new_page, vma->vm_page_prot));
page_remove_rmap(old_page, false);
if (!page_mapped(old_page))
@ -488,6 +498,10 @@ retry:
ref_ctr_updated = 1;
}
ret = 0;
if (!is_register && !PageAnon(old_page))
goto put_old;
ret = anon_vma_prepare(vma);
if (ret)
goto put_old;
@ -501,8 +515,30 @@ retry:
copy_highpage(new_page, old_page);
copy_to_page(new_page, vaddr, &opcode, UPROBE_SWBP_INSN_SIZE);
if (!is_register) {
struct page *orig_page;
pgoff_t index;
VM_BUG_ON_PAGE(!PageAnon(old_page), old_page);
index = vaddr_to_offset(vma, vaddr & PAGE_MASK) >> PAGE_SHIFT;
orig_page = find_get_page(vma->vm_file->f_inode->i_mapping,
index);
if (orig_page) {
if (PageUptodate(orig_page) &&
pages_identical(new_page, orig_page)) {
/* let go new_page */
put_page(new_page);
new_page = NULL;
}
put_page(orig_page);
}
}
ret = __replace_page(vma, vaddr, old_page, new_page);
put_page(new_page);
if (new_page)
put_page(new_page);
put_old:
put_page(old_page);