| Message ID | ae4845250ae9e7d000ca28fe90e64a331f664ce2.1679468982.git.lstoakes@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | further cleanup of vma_merge() | expand |
On 3/22/23 08:13, Lorenzo Stoakes wrote: > Rather than setting err = -1 and only resetting if we hit merge cases, > explicitly check the non-mergeable case to make it abundantly clear that we > only proceed with the rest if something is mergeable, default err to 0 and > only update if an error might occur. > > Move the merge_prev, merge_next cases closer to the logic determining curr, > next and reorder initial variables so they are more logically grouped. > > This has no functional impact. > > Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com> Reviewed-by: Vlastimil Babka <vbabka@suse.cz> Some nits: > --- > mm/mmap.c | 57 ++++++++++++++++++++++++++++--------------------------- > 1 file changed, 29 insertions(+), 28 deletions(-) > > diff --git a/mm/mmap.c b/mm/mmap.c > index 2a4f63716231..642f3d063be1 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -909,18 +909,18 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, > struct vm_userfaultfd_ctx vm_userfaultfd_ctx, > struct anon_vma_name *anon_name) > { > - pgoff_t pglen = (end - addr) >> PAGE_SHIFT; > - pgoff_t vma_pgoff; > struct vm_area_struct *curr, *next, *res; > struct vm_area_struct *vma, *adjust, *remove, *remove2; > - int err = -1; > + struct vma_prepare vp; > + pgoff_t vma_pgoff; > + int err = 0; > bool merge_prev = false; > bool merge_next = false; > bool vma_expanded = false; > - struct vma_prepare vp; > + unsigned long vma_start = addr; > unsigned long vma_end = end; > + pgoff_t pglen = (end - addr) >> PAGE_SHIFT; > long adj_start = 0; > - unsigned long vma_start = addr; > > validate_mm(mm); > /* > @@ -939,36 +939,38 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, > else > next = NULL; /* case 5 */ > > - /* > - * By default, we return prev. Cases 3, 4, 8 will instead return next > - * and cases 3, 8 will also update vma to point at next. > - */ > - res = vma = prev; > - > - /* Verify some invariant that must be enforced by the caller. */ > - VM_WARN_ON(prev && addr <= prev->vm_start); > - VM_WARN_ON(curr && (addr != curr->vm_start || end > curr->vm_end)); > - VM_WARN_ON(addr >= end); > - > if (prev) { > vma_start = prev->vm_start; > vma_pgoff = prev->vm_pgoff; > + > /* Can we merge the predecessor? */ > - if (prev->vm_end == addr && mpol_equal(vma_policy(prev), policy) > + if (addr == prev->vm_end && mpol_equal(vma_policy(prev), policy) > && can_vma_merge_after(prev, vm_flags, anon_vma, file, > - pgoff, vm_userfaultfd_ctx, anon_name)) { > + pgoff, vm_userfaultfd_ctx, anon_name)) { > merge_prev = true; > vma_prev(vmi); > } > } > > /* Can we merge the successor? */ > - if (next && mpol_equal(policy, vma_policy(next)) && > - can_vma_merge_before(next, vm_flags, > - anon_vma, file, pgoff+pglen, > - vm_userfaultfd_ctx, anon_name)) { > - merge_next = true; > - } > + merge_next = next && mpol_equal(policy, vma_policy(next)) && > + can_vma_merge_before(next, vm_flags, > + anon_vma, file, pgoff+pglen, > + vm_userfaultfd_ctx, anon_name); Not a great fan of this, I think the if() is more readable, but if you and Liam agree, I won't mind much. Either way could consolidate the parameters on less lines maybe. > + > + if (!merge_prev && !merge_next) > + return NULL; /* Not mergeable. */ > + > + /* > + * By default, we return prev. Cases 3, 4, 8 will instead return next > + * and cases 3, 8 will also update vma to point at next. > + */ > + res = vma = prev; > + > + /* Verify some invariant that must be enforced by the caller. */ > + VM_WARN_ON(prev && addr <= prev->vm_start); > + VM_WARN_ON(curr && (addr != curr->vm_start || end > curr->vm_end)); > + VM_WARN_ON(addr >= end); > > remove = remove2 = adjust = NULL; > /* Can we merge both the predecessor and the successor? */ > @@ -984,7 +986,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, > err = dup_anon_vma(prev, curr); > } > } else if (merge_prev) { > - err = 0; /* case 2 */ > + /* case 2 */ Move the comment from this now weirdly empty line to the "else if" one above? > if (curr) { > err = dup_anon_vma(prev, curr); > if (end == curr->vm_end) { /* case 7 */ > @@ -994,7 +996,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, > adj_start = (end - curr->vm_start); > } > } > - } else if (merge_next) { > + } else { /* merge_next */ > res = next; > if (prev && addr < prev->vm_end) { /* case 4 */ > vma_end = addr; > @@ -1010,7 +1012,6 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, > vma_start = addr; > vma_end = next->vm_end; > vma_pgoff = next->vm_pgoff; > - err = 0; > if (curr) { /* case 8 */ > vma_pgoff = curr->vm_pgoff; > remove = curr; > @@ -1019,7 +1020,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, > } > } > > - /* Cannot merge or error in anon_vma clone */ > + /* Error in anon_vma clone. */ > if (err) > return NULL; >
* Vlastimil Babka <vbabka@suse.cz> [230322 05:28]: > On 3/22/23 08:13, Lorenzo Stoakes wrote: > > Rather than setting err = -1 and only resetting if we hit merge cases, > > explicitly check the non-mergeable case to make it abundantly clear that we > > only proceed with the rest if something is mergeable, default err to 0 and > > only update if an error might occur. > > > > Move the merge_prev, merge_next cases closer to the logic determining curr, > > next and reorder initial variables so they are more logically grouped. > > > > This has no functional impact. > > > > Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com> > > Reviewed-by: Vlastimil Babka <vbabka@suse.cz> > > Some nits: > > > --- > > mm/mmap.c | 57 ++++++++++++++++++++++++++++--------------------------- > > 1 file changed, 29 insertions(+), 28 deletions(-) > > > > diff --git a/mm/mmap.c b/mm/mmap.c > > index 2a4f63716231..642f3d063be1 100644 > > --- a/mm/mmap.c > > +++ b/mm/mmap.c > > @@ -909,18 +909,18 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, > > struct vm_userfaultfd_ctx vm_userfaultfd_ctx, > > struct anon_vma_name *anon_name) > > { > > - pgoff_t pglen = (end - addr) >> PAGE_SHIFT; > > - pgoff_t vma_pgoff; > > struct vm_area_struct *curr, *next, *res; > > struct vm_area_struct *vma, *adjust, *remove, *remove2; > > - int err = -1; > > + struct vma_prepare vp; > > + pgoff_t vma_pgoff; > > + int err = 0; > > bool merge_prev = false; > > bool merge_next = false; > > bool vma_expanded = false; > > - struct vma_prepare vp; > > + unsigned long vma_start = addr; > > unsigned long vma_end = end; > > + pgoff_t pglen = (end - addr) >> PAGE_SHIFT; > > long adj_start = 0; > > - unsigned long vma_start = addr; > > > > validate_mm(mm); > > /* > > @@ -939,36 +939,38 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, > > else > > next = NULL; /* case 5 */ > > > > - /* > > - * By default, we return prev. Cases 3, 4, 8 will instead return next > > - * and cases 3, 8 will also update vma to point at next. > > - */ > > - res = vma = prev; > > - > > - /* Verify some invariant that must be enforced by the caller. */ > > - VM_WARN_ON(prev && addr <= prev->vm_start); > > - VM_WARN_ON(curr && (addr != curr->vm_start || end > curr->vm_end)); > > - VM_WARN_ON(addr >= end); > > - > > if (prev) { > > vma_start = prev->vm_start; > > vma_pgoff = prev->vm_pgoff; > > + > > /* Can we merge the predecessor? */ > > - if (prev->vm_end == addr && mpol_equal(vma_policy(prev), policy) > > + if (addr == prev->vm_end && mpol_equal(vma_policy(prev), policy) > > && can_vma_merge_after(prev, vm_flags, anon_vma, file, > > - pgoff, vm_userfaultfd_ctx, anon_name)) { > > + pgoff, vm_userfaultfd_ctx, anon_name)) { > > merge_prev = true; > > vma_prev(vmi); > > } > > } > > > > /* Can we merge the successor? */ > > - if (next && mpol_equal(policy, vma_policy(next)) && > > - can_vma_merge_before(next, vm_flags, > > - anon_vma, file, pgoff+pglen, > > - vm_userfaultfd_ctx, anon_name)) { > > - merge_next = true; > > - } > > + merge_next = next && mpol_equal(policy, vma_policy(next)) && > > + can_vma_merge_before(next, vm_flags, > > + anon_vma, file, pgoff+pglen, > > + vm_userfaultfd_ctx, anon_name); > > Not a great fan of this, I think the if() is more readable, but if you and > Liam agree, I won't mind much. Either way could consolidate the parameters > on less lines maybe. I think it's more readable with the if() as well, fwiw. If you revert this to an if(), then you should keep the braces as it looks very awkward without them. > > > + > > + if (!merge_prev && !merge_next) > > + return NULL; /* Not mergeable. */ > > + > > + /* > > + * By default, we return prev. Cases 3, 4, 8 will instead return next > > + * and cases 3, 8 will also update vma to point at next. > > + */ > > + res = vma = prev; > > + > > + /* Verify some invariant that must be enforced by the caller. */ > > + VM_WARN_ON(prev && addr <= prev->vm_start); > > + VM_WARN_ON(curr && (addr != curr->vm_start || end > curr->vm_end)); > > + VM_WARN_ON(addr >= end); > > > > remove = remove2 = adjust = NULL; > > /* Can we merge both the predecessor and the successor? */ > > @@ -984,7 +986,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, > > err = dup_anon_vma(prev, curr); > > } > > } else if (merge_prev) { > > - err = 0; /* case 2 */ > > + /* case 2 */ > > Move the comment from this now weirdly empty line to the "else if" one above? Yeah, this also makes sense to me, and brings it in line with case 8/4, etc. > > > if (curr) { > > err = dup_anon_vma(prev, curr); > > if (end == curr->vm_end) { /* case 7 */ > > @@ -994,7 +996,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, > > adj_start = (end - curr->vm_start); > > } > > } > > - } else if (merge_next) { > > + } else { /* merge_next */ > > res = next; > > if (prev && addr < prev->vm_end) { /* case 4 */ > > vma_end = addr; > > @@ -1010,7 +1012,6 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, > > vma_start = addr; > > vma_end = next->vm_end; > > vma_pgoff = next->vm_pgoff; > > - err = 0; > > if (curr) { /* case 8 */ > > vma_pgoff = curr->vm_pgoff; > > remove = curr; > > @@ -1019,7 +1020,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, > > } > > } > > > > - /* Cannot merge or error in anon_vma clone */ > > + /* Error in anon_vma clone. */ > > if (err) > > return NULL; > > > >
diff --git a/mm/mmap.c b/mm/mmap.c index 2a4f63716231..642f3d063be1 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -909,18 +909,18 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, struct vm_userfaultfd_ctx vm_userfaultfd_ctx, struct anon_vma_name *anon_name) { - pgoff_t pglen = (end - addr) >> PAGE_SHIFT; - pgoff_t vma_pgoff; struct vm_area_struct *curr, *next, *res; struct vm_area_struct *vma, *adjust, *remove, *remove2; - int err = -1; + struct vma_prepare vp; + pgoff_t vma_pgoff; + int err = 0; bool merge_prev = false; bool merge_next = false; bool vma_expanded = false; - struct vma_prepare vp; + unsigned long vma_start = addr; unsigned long vma_end = end; + pgoff_t pglen = (end - addr) >> PAGE_SHIFT; long adj_start = 0; - unsigned long vma_start = addr; validate_mm(mm); /* @@ -939,36 +939,38 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, else next = NULL; /* case 5 */ - /* - * By default, we return prev. Cases 3, 4, 8 will instead return next - * and cases 3, 8 will also update vma to point at next. - */ - res = vma = prev; - - /* Verify some invariant that must be enforced by the caller. */ - VM_WARN_ON(prev && addr <= prev->vm_start); - VM_WARN_ON(curr && (addr != curr->vm_start || end > curr->vm_end)); - VM_WARN_ON(addr >= end); - if (prev) { vma_start = prev->vm_start; vma_pgoff = prev->vm_pgoff; + /* Can we merge the predecessor? */ - if (prev->vm_end == addr && mpol_equal(vma_policy(prev), policy) + if (addr == prev->vm_end && mpol_equal(vma_policy(prev), policy) && can_vma_merge_after(prev, vm_flags, anon_vma, file, - pgoff, vm_userfaultfd_ctx, anon_name)) { + pgoff, vm_userfaultfd_ctx, anon_name)) { merge_prev = true; vma_prev(vmi); } } /* Can we merge the successor? */ - if (next && mpol_equal(policy, vma_policy(next)) && - can_vma_merge_before(next, vm_flags, - anon_vma, file, pgoff+pglen, - vm_userfaultfd_ctx, anon_name)) { - merge_next = true; - } + merge_next = next && mpol_equal(policy, vma_policy(next)) && + can_vma_merge_before(next, vm_flags, + anon_vma, file, pgoff+pglen, + vm_userfaultfd_ctx, anon_name); + + if (!merge_prev && !merge_next) + return NULL; /* Not mergeable. */ + + /* + * By default, we return prev. Cases 3, 4, 8 will instead return next + * and cases 3, 8 will also update vma to point at next. + */ + res = vma = prev; + + /* Verify some invariant that must be enforced by the caller. */ + VM_WARN_ON(prev && addr <= prev->vm_start); + VM_WARN_ON(curr && (addr != curr->vm_start || end > curr->vm_end)); + VM_WARN_ON(addr >= end); remove = remove2 = adjust = NULL; /* Can we merge both the predecessor and the successor? */ @@ -984,7 +986,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, err = dup_anon_vma(prev, curr); } } else if (merge_prev) { - err = 0; /* case 2 */ + /* case 2 */ if (curr) { err = dup_anon_vma(prev, curr); if (end == curr->vm_end) { /* case 7 */ @@ -994,7 +996,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, adj_start = (end - curr->vm_start); } } - } else if (merge_next) { + } else { /* merge_next */ res = next; if (prev && addr < prev->vm_end) { /* case 4 */ vma_end = addr; @@ -1010,7 +1012,6 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, vma_start = addr; vma_end = next->vm_end; vma_pgoff = next->vm_pgoff; - err = 0; if (curr) { /* case 8 */ vma_pgoff = curr->vm_pgoff; remove = curr; @@ -1019,7 +1020,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, } } - /* Cannot merge or error in anon_vma clone */ + /* Error in anon_vma clone. */ if (err) return NULL;
Rather than setting err = -1 and only resetting if we hit merge cases, explicitly check the non-mergeable case to make it abundantly clear that we only proceed with the rest if something is mergeable, default err to 0 and only update if an error might occur. Move the merge_prev, merge_next cases closer to the logic determining curr, next and reorder initial variables so they are more logically grouped. This has no functional impact. Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com> --- mm/mmap.c | 57 ++++++++++++++++++++++++++++--------------------------- 1 file changed, 29 insertions(+), 28 deletions(-)