The patch titled
Subject: uprobe: use original page when all uprobes are removed
has been added to the -mm tree. Its filename is
uprobe-use-original-page-when-all-uprobes-are-removed.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/uprobe-use-original-page-when-all-uprobes-are-removed.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/uprobe-use-original-page-when-all-uprobes-are-removed.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Song Liu <songliubraving@xxxxxx>
Subject: uprobe: use original page when all uprobes are removed
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). As suggested by Oleg, we unmap the
old_page and let the original page fault in.
Link: http://lkml.kernel.org/r/20190726054654.1623433-3-songliubraving@xxxxxx
Signed-off-by: Song Liu <songliubraving@xxxxxx>
Suggested-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Matthew Wilcox <matthew.wilcox@xxxxxxxxxx>
Cc: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
Cc: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Cc: William Kucharski <william.kucharski@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/events/uprobes.c | 62 ++++++++++++++++++++++++++++----------
1 file changed, 47 insertions(+), 15 deletions(-)
--- a/kernel/events/uprobes.c~uprobe-use-original-page-when-all-uprobes-are-removed
+++ a/kernel/events/uprobes.c
@@ -143,10 +143,12 @@ static loff_t vaddr_to_offset(struct vm_
*
* @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
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 +181,18 @@ static int __replace_page(struct vm_area
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);
+ }
if (!PageAnon(old_page)) {
dec_mm_counter(mm, mm_counter_file(old_page));
@@ -194,8 +201,9 @@ static int __replace_page(struct vm_area
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))
@@ -501,8 +509,32 @@ retry:
copy_highpage(new_page, old_page);
copy_to_page(new_page, vaddr, &opcode, UPROBE_SWBP_INSN_SIZE);
+ /* try orig_page only for unregister and anonymous old_page */
+ if (!is_register && PageAnon(old_page)) {
+ struct page *orig_page;
+ pgoff_t index;
+
+ 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;
+
+ /* dec_mm_counter for old_page */
+ dec_mm_counter(mm, MM_ANONPAGES);
+ }
+ 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);
_
Patches currently in -mm which might be from songliubraving@xxxxxx are
mm-move-memcmp_pages-and-pages_identical.patch
uprobe-use-original-page-when-all-uprobes-are-removed.patch
mm-thp-introduce-foll_split_pmd.patch
uprobe-use-foll_split_pmd-instead-of-foll_split.patch
