superrob1500
/
mirror-linux
mirror of https://github.com/torvalds/linux
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

mm: make vmg->target consistent and further simplify commit_merge() 

It is confusing for vmg->target to sometimes be the target merged VMA and
in one case not.

Fix this by having commit_merge() use its awareness of the
vmg->_adjust_next_start case to know that it is manipulating a separate
vma, abstracted in the 'vma' local variable.

Place removal and adjust VMA determination logic into
init_multi_vma_prep(), as the flags give us enough information to do so,
and since this is the function that sets up the vma_prepare struct it
makes sense to do so here.

Doing this significantly simplifies commit_merge(), allowing us to
eliminate the 'merge_target' handling, initialise the VMA iterator in a
more sensible place and simply return vmg->target consistently.

This also allows us to simplify setting vmg->target in
vma_merge_existing_range() since we are then left only with two cases -
merge left (or both) where the target is vmg->prev or merge right in which
the target is vmg->next.

This makes it easy for somebody reading the code to know what VMA will
actually be the one returned and merged into and removes a great deal of
the confusing 'adjust' nonsense.

This patch has no change in functional behaviour.

Link: https://lkml.kernel.org/r/50f96e31ab1980eaaf1006e34a4f6e6dad9320b8.1738326519.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
pull/1193/head
Lorenzo Stoakes 2025-01-31 12:31:52 +00:00 committed by Andrew Morton
parent fe3e9cf0d7
commit 0e5ffe9b2b
2 changed files with 62 additions and 63 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

117
mm/vma.c
View File

@ -106,24 +106,40 @@ static inline bool are_anon_vmas_compatible(struct vm_area_struct *vma1,
* init_multi_vma_prep() - Initializer for struct vma_prepare * init_multi_vma_prep() - Initializer for struct vma_prepare
* @vp: The vma_prepare struct * @vp: The vma_prepare struct
* @vma: The vma that will be altered once locked * @vma: The vma that will be altered once locked
* @next: The next vma if it is to be adjusted * @vmg: The merge state that will be used to determine adjustment and VMA
* @remove: The first vma to be removed * removal.
* @remove2: The second vma to be removed
*/ */
static void init_multi_vma_prep(struct vma_prepare *vp, static void init_multi_vma_prep(struct vma_prepare *vp,
struct vm_area_struct *vma, struct vm_area_struct *vma,
struct vm_area_struct *next, struct vma_merge_struct *vmg)
struct vm_area_struct *remove,
struct vm_area_struct *remove2)
{ {
struct vm_area_struct *adjust;
struct vm_area_struct **remove = &vp->remove;
memset(vp, 0, sizeof(struct vma_prepare)); memset(vp, 0, sizeof(struct vma_prepare));
vp->vma = vma; vp->vma = vma;
vp->anon_vma = vma->anon_vma; vp->anon_vma = vma->anon_vma;
vp->remove = remove ? remove : remove2;
vp->remove2 = remove ? remove2 : NULL; if (vmg && vmg->__remove_middle) {
vp->adj_next = next; *remove = vmg->middle;
if (!vp->anon_vma && next) remove = &vp->remove2;
vp->anon_vma = next->anon_vma; }
if (vmg && vmg->__remove_next)
*remove = vmg->next;
if (vmg && vmg->__adjust_middle_start)
adjust = vmg->middle;
else if (vmg && vmg->__adjust_next_start)
adjust = vmg->next;
else
adjust = NULL;
vp->adj_next = adjust;
if (!vp->anon_vma && adjust)
vp->anon_vma = adjust->anon_vma;
VM_WARN_ON(vp->anon_vma && adjust && adjust->anon_vma &&
vp->anon_vma != adjust->anon_vma);
vp->file = vma->vm_file; vp->file = vma->vm_file;
if (vp->file) if (vp->file)
@ -360,7 +376,7 @@ again:
*/ */
static void init_vma_prep(struct vma_prepare *vp, struct vm_area_struct *vma) static void init_vma_prep(struct vma_prepare *vp, struct vm_area_struct *vma)
{ {
init_multi_vma_prep(vp, vma, NULL, NULL, NULL); init_multi_vma_prep(vp, vma, NULL);
} }
/* /*
@ -634,76 +650,63 @@ void validate_mm(struct mm_struct *mm)
*/ */
static struct vm_area_struct *commit_merge(struct vma_merge_struct *vmg) static struct vm_area_struct *commit_merge(struct vma_merge_struct *vmg)
{ {
struct vm_area_struct *remove = NULL; struct vm_area_struct *vma;
struct vm_area_struct *remove2 = NULL;
struct vma_prepare vp; struct vma_prepare vp;
struct vm_area_struct *adjust = NULL; struct vm_area_struct *adjust;
long adj_start; long adj_start;
bool merge_target;
/* /*
* If modifying an existing VMA and we don't remove vmg->middle, then we * If modifying an existing VMA and we don't remove vmg->middle, then we
* shrink the adjacent VMA. * shrink the adjacent VMA.
*/ */
if (vmg->__adjust_middle_start) { if (vmg->__adjust_middle_start) {
vma = vmg->target;
adjust = vmg->middle; adjust = vmg->middle;
/* The POSITIVE value by which we offset vmg->middle->vm_start. */ /* The POSITIVE value by which we offset vmg->middle->vm_start. */
adj_start = vmg->end - vmg->middle->vm_start; adj_start = vmg->end - vmg->middle->vm_start;
merge_target = true;
/* Note: vma iterator must be pointing to 'start'. */
vma_iter_config(vmg->vmi, vmg->start, vmg->end);
} else if (vmg->__adjust_next_start) { } else if (vmg->__adjust_next_start) {
/*
* In this case alone, the VMA we manipulate is vmg->middle, but
* we ultimately return vmg->next.
*/
vma = vmg->middle;
adjust = vmg->next; adjust = vmg->next;
/* The NEGATIVE value by which we offset vmg->next->vm_start. */ /* The NEGATIVE value by which we offset vmg->next->vm_start. */
adj_start = -(vmg->middle->vm_end - vmg->end); adj_start = -(vmg->middle->vm_end - vmg->end);
/*
* In all cases but this - merge right, shrink next - we write vma_iter_config(vmg->vmi, vmg->next->vm_start + adj_start,
* vmg->target to the maple tree and return this as the merged VMA. vmg->next->vm_end);
*/
merge_target = false;
} else { } else {
vma = vmg->target;
adjust = NULL; adjust = NULL;
adj_start = 0; adj_start = 0;
merge_target = true;
}
if (vmg->__remove_middle)
remove = vmg->middle;
if (vmg->__remove_next)
remove2 = vmg->next;
init_multi_vma_prep(&vp, vmg->target, adjust, remove, remove2);
VM_WARN_ON(vp.anon_vma && adjust && adjust->anon_vma &&
vp.anon_vma != adjust->anon_vma);
if (merge_target) {
/* Note: vma iterator must be pointing to 'start'. */ /* Note: vma iterator must be pointing to 'start'. */
vma_iter_config(vmg->vmi, vmg->start, vmg->end); vma_iter_config(vmg->vmi, vmg->start, vmg->end);
} else {
vma_iter_config(vmg->vmi, adjust->vm_start + adj_start,
adjust->vm_end);
} }
if (vma_iter_prealloc(vmg->vmi, vmg->target)) init_multi_vma_prep(&vp, vma, vmg);
if (vma_iter_prealloc(vmg->vmi, vma))
return NULL; return NULL;
vma_prepare(&vp); vma_prepare(&vp);
vma_adjust_trans_huge(vmg->target, vmg->start, vmg->end, adj_start); vma_adjust_trans_huge(vma, vmg->start, vmg->end, adj_start);
vma_set_range(vmg->target, vmg->start, vmg->end, vmg->pgoff); vma_set_range(vma, vmg->start, vmg->end, vmg->pgoff);
if (merge_target)
vma_iter_store(vmg->vmi, vmg->target);
if (adj_start) { if (adj_start) {
adjust->vm_start += adj_start; adjust->vm_start += adj_start;
adjust->vm_pgoff += PHYS_PFN(adj_start); adjust->vm_pgoff += PHYS_PFN(adj_start);
if (!merge_target)
vma_iter_store(vmg->vmi, adjust);
} }
vma_complete(&vp, vmg->vmi, vmg->target->vm_mm); vma_iter_store(vmg->vmi, vmg->target);
return merge_target ? vmg->target : vmg->next; vma_complete(&vp, vmg->vmi, vma->vm_mm);
return vmg->target;
} }
/* We can only remove VMAs when merging if they do not have a close hook. */ /* We can only remove VMAs when merging if they do not have a close hook. */
@ -833,11 +836,15 @@ static __must_check struct vm_area_struct *vma_merge_existing_range(
/* No matter what happens, we will be adjusting middle. */ /* No matter what happens, we will be adjusting middle. */
vma_start_write(middle); vma_start_write(middle);
if (merge_left) if (merge_right) {
vma_start_write(prev);
if (merge_right)
vma_start_write(next); vma_start_write(next);
vmg->target = next;
}
if (merge_left) {
vma_start_write(prev);
vmg->target = prev;
}
if (merge_both) { if (merge_both) {
/* /*
@ -847,7 +854,6 @@ static __must_check struct vm_area_struct *vma_merge_existing_range(
* extend delete delete * extend delete delete
*/ */
vmg->target = prev;
vmg->start = prev->vm_start; vmg->start = prev->vm_start;
vmg->end = next->vm_end; vmg->end = next->vm_end;
vmg->pgoff = prev->vm_pgoff; vmg->pgoff = prev->vm_pgoff;
@ -868,7 +874,6 @@ static __must_check struct vm_area_struct *vma_merge_existing_range(
* extend shrink/delete * extend shrink/delete
*/ */
vmg->target = prev;
vmg->start = prev->vm_start; vmg->start = prev->vm_start;
vmg->pgoff = prev->vm_pgoff; vmg->pgoff = prev->vm_pgoff;
@ -892,7 +897,6 @@ static __must_check struct vm_area_struct *vma_merge_existing_range(
VM_WARN_ON_VMG(vmg->start > middle->vm_start && prev && middle != prev, vmg); VM_WARN_ON_VMG(vmg->start > middle->vm_start && prev && middle != prev, vmg);
if (vmg->__remove_middle) { if (vmg->__remove_middle) {
vmg->target = next;
vmg->end = next->vm_end; vmg->end = next->vm_end;
vmg->pgoff = next->vm_pgoff - pglen; vmg->pgoff = next->vm_pgoff - pglen;
} else { } else {
@ -903,7 +907,6 @@ static __must_check struct vm_area_struct *vma_merge_existing_range(
* merged VMA is NOT vmg->target, but rather vmg->next. * merged VMA is NOT vmg->target, but rather vmg->next.
*/ */
vmg->__adjust_next_start = true; vmg->__adjust_next_start = true;
vmg->target = middle;
vmg->start = middle->vm_start; vmg->start = middle->vm_start;
vmg->end = start; vmg->end = start;
vmg->pgoff = middle->vm_pgoff; vmg->pgoff = middle->vm_pgoff;

6
mm/vma.h
View File

@ -82,11 +82,7 @@ struct vma_merge_struct {
struct vm_area_struct *prev; struct vm_area_struct *prev;
struct vm_area_struct *middle; struct vm_area_struct *middle;
struct vm_area_struct *next; struct vm_area_struct *next;
/* /* This is the VMA we ultimately target to become the merged VMA. */
* This is the VMA we ultimately target to become the merged VMA, except
* for the one exception of merge right, shrink next (for details of
* this scenario see vma_merge_existing_range()).
*/
struct vm_area_struct *target; struct vm_area_struct *target;
/* /*
* Initially, the start, end, pgoff fields are provided by the caller * Initially, the start, end, pgoff fields are provided by the caller