The quilt patch titled
Subject: mm/mmap/vma_merge: set mid to NULL if not applicable
has been removed from the -mm tree. Its filename was
mm-mmap-vma_merge-set-mid-to-null-if-not-applicable.patch
This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: Vlastimil Babka <vbabka@xxxxxxx>
Subject: mm/mmap/vma_merge: set mid to NULL if not applicable
Date: Thu, 9 Mar 2023 12:12:54 +0100
There are several places where we test if 'mid' is really the area NNNN in
the diagram and the tests have two variants and are non-obvious to follow.
Instead, set 'mid' to NULL up-front if it's not the NNNN area, and
simplify the tests.
Also update the description in comment accordingly.
[vbabka@xxxxxxx: adjust/add comments as suggested by Lorenzo]
Link: https://lkml.kernel.org/r/def43190-53f7-a607-d1b0-b657565f4288@xxxxxxx
Link: https://lkml.kernel.org/r/20230309111258.24079-7-vbabka@xxxxxxx
Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
Reviewed-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
Cc: Lorenzo Stoakes <lstoakes@xxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/mmap.c | 23 +++++++++++++++--------
1 file changed, 15 insertions(+), 8 deletions(-)
--- a/mm/mmap.c~mm-mmap-vma_merge-set-mid-to-null-if-not-applicable
+++ a/mm/mmap.c
@@ -848,10 +848,12 @@ can_vma_merge_after(struct vm_area_struc
*
* The following mprotect cases have to be considered, where AAAA is
* the area passed down from mprotect_fixup, never extending beyond one
- * vma, PPPPPP is the prev vma specified, and NNNNNN the next vma after:
+ * vma, PPPP is the previous vma, NNNN is a vma that starts at the same
+ * address as AAAA and is of the same or larger span, and XXXX the next
+ * vma after AAAA:
*
* AAAA AAAA AAAA
- * PPPPPPNNNNNN PPPPPPXXXXXX PPPPPPNNNNNN
+ * PPPPPPXXXXXX PPPPPPXXXXXX PPPPPPNNNNNN
* cannot merge might become might become
* PPXXXXXXXXXX PPPPPPPPPPNN
* mmap, brk or case 4 below case 5 below
@@ -879,9 +881,10 @@ can_vma_merge_after(struct vm_area_struc
*
* In the code below:
* PPPP is represented by *prev
- * NNNN is represented by *mid (and possibly equal to *next)
- * XXXX is represented by *next or not represented at all.
- * AAAA is not represented - it will be merged or the function will return NULL
+ * NNNN is represented by *mid or not represented at all (NULL)
+ * XXXX is represented by *next or not represented at all (NULL)
+ * AAAA is not represented - it will be merged and the vma containing the
+ * area is returned, or the function will return NULL
*/
struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
struct vm_area_struct *prev, unsigned long addr,
@@ -918,6 +921,10 @@ struct vm_area_struct *vma_merge(struct
else
next = mid;
+ /* In cases 1 - 4 there's no NNNN vma */
+ if (mid && end <= mid->vm_start)
+ mid = NULL;
+
/* verify some invariant that must be enforced by the caller */
VM_WARN_ON(prev && addr <= prev->vm_start);
VM_WARN_ON(mid && end > mid->vm_end);
@@ -952,7 +959,7 @@ struct vm_area_struct *vma_merge(struct
remove = next; /* case 1 */
vma_end = next->vm_end;
err = dup_anon_vma(prev, next);
- if (mid != next) { /* case 6 */
+ if (mid) { /* case 6 */
remove = mid;
remove2 = next;
if (!next->anon_vma)
@@ -960,7 +967,7 @@ struct vm_area_struct *vma_merge(struct
}
} else if (merge_prev) {
err = 0; /* case 2 */
- if (mid && end > mid->vm_start) {
+ if (mid) {
err = dup_anon_vma(prev, mid);
if (end == mid->vm_end) { /* case 7 */
remove = mid;
@@ -982,7 +989,7 @@ struct vm_area_struct *vma_merge(struct
vma_end = next->vm_end;
vma_pgoff = next->vm_pgoff;
err = 0;
- if (mid != next) { /* case 8 */
+ if (mid) { /* case 8 */
vma_pgoff = mid->vm_pgoff;
remove = mid;
err = dup_anon_vma(next, mid);
_
Patches currently in -mm which might be from vbabka@xxxxxxx are
mm-page_alloc-use-check_pages_enabled-static-key-to-check-tail-pages.patch
