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
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
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------------------------------------------------------
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, 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@xxxxxx
Signed-off-by: Song Liu <songliubraving@xxxxxx>
Suggested-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Reviewed-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/events/uprobes.c | 66 +++++++++++++++++++++++++++++---------
1 file changed, 51 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 +181,20 @@ 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);
+ } 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
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);
_
Patches currently in -mm which might be from songliubraving@xxxxxx are
filemap-check-compound_headpage-mapping-in-filemap_fault.patch
filemap-check-compound_headpage-mapping-in-pagecache_get_page.patch
filemap-update-offset-check-in-filemap_fault.patch
mmthp-stats-for-file-backed-thp.patch
khugepaged-rename-collapse_shmem-and-khugepaged_scan_shmem.patch
mmthp-add-read-only-thp-support-for-non-shmem-fs.patch
mmthp-add-read-only-thp-support-for-non-shmem-fs-fix.patch
mmthp-add-read-only-thp-support-for-non-shmem-fs-fix-2.patch
mmthp-avoid-writes-to-file-with-thp-in-pagecache.patch
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
khugepaged-enable-collapse-pmd-for-pte-mapped-thp.patch
uprobe-collapse-thp-pmd-after-removing-all-uprobes.patch
