mm/mmap: introduce init_vma_prep() and init_multi_vma_prep()

Add init_vma_prep() and init_multi_vma_prep() to set up the struct
vma_prepare.  This is to abstract the locking when adjusting the VMAs.

Also change __vma_adjust() variable remove_next int in favour of a pointer
to the VMA to remove.  Rename next_next to remove2 since this better
reflects its use.

Link: https://lkml.kernel.org/r/20230120162650.984577-43-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/mmap.c b/mm/mmap.c
index b5bf70d..e259b33 100644 (file)
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -457,6 +457,45 @@ static int vma_link(struct mm_struct *mm, struct vm_area_struct *vma)
        return 0;
 }
 
+/*
+ * init_multi_vma_prep() - Initializer for struct vma_prepare
+ * @vp: The vma_prepare struct
+ * @vma: The vma that will be altered once locked
+ * @next: The next vma if it is to be adjusted
+ * @remove: The first vma to be removed
+ * @remove2: The second vma to be removed
+ */
+static inline void init_multi_vma_prep(struct vma_prepare *vp,
+               struct vm_area_struct *vma, struct vm_area_struct *next,
+               struct vm_area_struct *remove, struct vm_area_struct *remove2)
+{
+       memset(vp, 0, sizeof(struct vma_prepare));
+       vp->vma = vma;
+       vp->anon_vma = vma->anon_vma;
+       vp->remove = remove;
+       vp->remove2 = remove2;
+       vp->adj_next = next;
+       if (!vp->anon_vma && next)
+               vp->anon_vma = next->anon_vma;
+
+       vp->file = vma->vm_file;
+       if (vp->file)
+               vp->mapping = vma->vm_file->f_mapping;
+
+}
+
+/*
+ * init_vma_prep() - Initializer wrapper for vma_prepare struct
+ * @vp: The vma_prepare struct
+ * @vma: The vma that will be altered once locked
+ */
+static inline void init_vma_prep(struct vma_prepare *vp,
+                                struct vm_area_struct *vma)
+{
+       init_multi_vma_prep(vp, vma, NULL, NULL, NULL);
+}
+
+
 /*
  * vma_prepare() - Helper function for handling locking VMAs prior to altering
  * @vp: The initialized vma_prepare struct
@@ -566,7 +605,7 @@ again:
 
                /*
                 * In mprotect's case 6 (see comments on vma_merge),
-                * we must remove next_next too.
+                * we must remove the one after next as well.
                 */
                if (vp->remove2) {
                        vp->remove = vp->remove2;
@@ -599,17 +638,14 @@ inline int vma_expand(struct vma_iterator *vmi, struct vm_area_struct *vma,
                      unsigned long start, unsigned long end, pgoff_t pgoff,
                      struct vm_area_struct *next)
 {
+       bool remove_next = false;
        struct vma_prepare vp;
 
-       memset(&vp, 0, sizeof(vp));
-       vp.vma = vma;
-       vp.anon_vma = vma->anon_vma;
        if (next && (vma != next) && (end == next->vm_end)) {
-               vp.remove = next;
+               remove_next = true;
                if (next->anon_vma && !vma->anon_vma) {
                        int error;
 
-                       vp.anon_vma = next->anon_vma;
                        vma->anon_vma = next->anon_vma;
                        error = anon_vma_clone(vma, next);
                        if (error)
@@ -617,6 +653,7 @@ inline int vma_expand(struct vma_iterator *vmi, struct vm_area_struct *vma,
                }
        }
 
+       init_multi_vma_prep(&vp, vma, NULL, remove_next ? next : NULL, NULL);
        /* Not merging but overwriting any part of next is not handled. */
        VM_WARN_ON(next && !vp.remove &&
                  next != vma && end > next->vm_start);
@@ -627,11 +664,6 @@ inline int vma_expand(struct vma_iterator *vmi, struct vm_area_struct *vma,
                goto nomem;
 
        vma_adjust_trans_huge(vma, start, end, 0);
-
-       vp.file = vma->vm_file;
-       if (vp.file)
-               vp.mapping = vp.file->f_mapping;
-
        /* VMA iterator points to previous, so set to start if necessary */
        if (vma_iter_addr(vmi) != start)
                vma_iter_set(vmi, start);
@@ -662,14 +694,13 @@ int __vma_adjust(struct vma_iterator *vmi, struct vm_area_struct *vma,
        struct vm_area_struct *insert, struct vm_area_struct *expand)
 {
        struct mm_struct *mm = vma->vm_mm;
-       struct vm_area_struct *next_next = NULL;        /* uninit var warning */
+       struct vm_area_struct *remove2 = NULL;
+       struct vm_area_struct *remove = NULL;
        struct vm_area_struct *next = find_vma(mm, vma->vm_end);
        struct vm_area_struct *orig_vma = vma;
-       struct anon_vma *anon_vma = NULL;
        struct file *file = vma->vm_file;
        bool vma_changed = false;
        long adjust_next = 0;
-       int remove_next = 0;
        struct vm_area_struct *exporter = NULL, *importer = NULL;
        struct vma_prepare vma_prep;
 
@@ -688,25 +719,24 @@ int __vma_adjust(struct vma_iterator *vmi, struct vm_area_struct *vma,
                                 */
                                VM_WARN_ON(end != next->vm_end);
                                /*
-                                * remove_next == 3 means we're
-                                * removing "vma" and that to do so we
+                                * we're removing "vma" and that to do so we
                                 * swapped "vma" and "next".
                                 */
-                               remove_next = 3;
                                VM_WARN_ON(file != next->vm_file);
                                swap(vma, next);
+                               remove = next;
                        } else {
                                VM_WARN_ON(expand != vma);
                                /*
-                                * case 1, 6, 7, remove_next == 2 is case 6,
-                                * remove_next == 1 is case 1 or 7.
+                                * case 1, 6, 7, remove next.
+                                * case 6 also removes the one beyond next
                                 */
-                               remove_next = 1 + (end > next->vm_end);
-                               if (remove_next == 2)
-                                       next_next = find_vma(mm, next->vm_end);
+                               remove = next;
+                               if (end > next->vm_end)
+                                       remove2 = find_vma(mm, next->vm_end);
 
-                               VM_WARN_ON(remove_next == 2 &&
-                                          end != next_next->vm_end);
+                               VM_WARN_ON(remove2 != NULL &&
+                                          end != remove2->vm_end);
                        }
 
                        exporter = next;
@@ -716,8 +746,8 @@ int __vma_adjust(struct vma_iterator *vmi, struct vm_area_struct *vma,
                         * If next doesn't have anon_vma, import from vma after
                         * next, if the vma overlaps with it.
                         */
-                       if (remove_next == 2 && !next->anon_vma)
-                               exporter = next_next;
+                       if (remove2 != NULL && !next->anon_vma)
+                               exporter = remove2;
 
                } else if (end > next->vm_start) {
                        /*
@@ -758,30 +788,14 @@ int __vma_adjust(struct vma_iterator *vmi, struct vm_area_struct *vma,
        if (vma_iter_prealloc(vmi))
                return -ENOMEM;
 
-       anon_vma = vma->anon_vma;
-       if (!anon_vma && adjust_next)
-               anon_vma = next->anon_vma;
-
-       if (anon_vma)
-               VM_WARN_ON(adjust_next && next->anon_vma &&
-                          anon_vma != next->anon_vma);
-
        vma_adjust_trans_huge(orig_vma, start, end, adjust_next);
 
-       memset(&vma_prep, 0, sizeof(vma_prep));
-       vma_prep.vma = vma;
-       vma_prep.anon_vma = anon_vma;
-       vma_prep.file = file;
-       if (adjust_next)
-               vma_prep.adj_next = next;
-       if (file)
-               vma_prep.mapping = file->f_mapping;
-       vma_prep.insert = insert;
-       if (remove_next) {
-               vma_prep.remove = next;
-               vma_prep.remove2 = next_next;
-       }
+       init_multi_vma_prep(&vma_prep, vma, adjust_next ? next : NULL, remove,
+                           remove2);
+       VM_WARN_ON(vma_prep.anon_vma && adjust_next && next->anon_vma &&
+                  vma_prep.anon_vma != next->anon_vma);
 
+       vma_prep.insert = insert;
        vma_prepare(&vma_prep);
 
        if (start != vma->vm_start) {