torvalds/linux
3
0
Fork 0
mirror of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git synced 2026-03-22 07:27:12 +08:00
Code Issues Packages Projects Releases Wiki Activity

ksm: replace function unmerge_ksm_pages with break_ksm

Browse Source 
Function unmerge_ksm_pages() is unnecessary since now break_ksm() walks an
address range.  So replace it with break_ksm().

Link: https://lkml.kernel.org/r/20251105184912.186329-4-pedrodemargomes@gmail.com
Signed-off-by: Pedro Demarchi Gomes <pedrodemargomes@gmail.com>
Suggested-by: David Hildenbrand (Red Hat) <david@kernel.org>
Acked-by: David Hildenbrand (Red Hat) <david@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Pedro Demarchi Gomes
2025-11-05 15:49:12 -03:00
committed by Andrew Morton
parent 5d4939fc22
commit 05c3fa9c9f
1 changed files with 16 additions and 24 deletions
Download Patch File Download Diff File Expand all files Collapse all files

40
mm/ksm.c
View File

@@ -665,6 +665,18 @@ static const struct mm_walk_ops break_ksm_lock_vma_ops = {
};
/*
* Though it's very tempting to unmerge rmap_items from stable tree rather
* than check every pte of a given vma, the locking doesn't quite work for
* that - an rmap_item is assigned to the stable tree after inserting ksm
* page and upping mmap_lock. Nor does it fit with the way we skip dup'ing
* rmap_items from parent to child at fork time (so as not to waste time
* if exit comes before the next scan reaches it).
*
* Similarly, although we'd like to remove rmap_items (so updating counts
* and freeing memory) when unmerging an area, it's easier to leave that
* to the next pass of ksmd - consider, for example, how ksmd might be
* in cmp_and_merge_page on one of the rmap_items we would be removing.
*
* We use break_ksm to break COW on a ksm page by triggering unsharing,
* such that the ksm page will get replaced by an exclusive anonymous page.
*
@@ -1071,25 +1083,6 @@ static void remove_trailing_rmap_items(struct ksm_rmap_item **rmap_list)
}
}
/*
* Though it's very tempting to unmerge rmap_items from stable tree rather
* than check every pte of a given vma, the locking doesn't quite work for
* that - an rmap_item is assigned to the stable tree after inserting ksm
* page and upping mmap_lock. Nor does it fit with the way we skip dup'ing
* rmap_items from parent to child at fork time (so as not to waste time
* if exit comes before the next scan reaches it).
*
* Similarly, although we'd like to remove rmap_items (so updating counts
* and freeing memory) when unmerging an area, it's easier to leave that
* to the next pass of ksmd - consider, for example, how ksmd might be
* in cmp_and_merge_page on one of the rmap_items we would be removing.
*/
static int unmerge_ksm_pages(struct vm_area_struct *vma,
unsigned long start, unsigned long end, bool lock_vma)
{
return break_ksm(vma, start, end, lock_vma);
}
static inline
struct ksm_stable_node *folio_stable_node(const struct folio *folio)
{
@@ -1227,8 +1220,7 @@ static int unmerge_and_remove_all_rmap_items(void)
for_each_vma(vmi, vma) {
if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma)
continue;
err = unmerge_ksm_pages(vma,
vma->vm_start, vma->vm_end, false);
err = break_ksm(vma, vma->vm_start, vma->vm_end, false);
if (err)
goto error;
}
@@ -2855,7 +2847,7 @@ static int __ksm_del_vma(struct vm_area_struct *vma)
return 0;
if (vma->anon_vma) {
err = unmerge_ksm_pages(vma, vma->vm_start, vma->vm_end, true);
err = break_ksm(vma, vma->vm_start, vma->vm_end, true);
if (err)
return err;
}
@@ -3007,7 +2999,7 @@ int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
return 0; /* just ignore the advice */
if (vma->anon_vma) {
err = unmerge_ksm_pages(vma, start, end, true);
err = break_ksm(vma, start, end, true);
if (err)
return err;
}
@@ -3389,7 +3381,7 @@ static int ksm_memory_callback(struct notifier_block *self,
* Prevent ksm_do_scan(), unmerge_and_remove_all_rmap_items()
* and remove_all_stable_nodes() while memory is going offline:
* it is unsafe for them to touch the stable tree at this time.
* But unmerge_ksm_pages(), rmap lookups and other entry points
* But break_ksm(), rmap lookups and other entry points
* which do not need the ksm_thread_mutex are all safe.
*/
mutex_lock(&ksm_thread_mutex);