From cf51e86dfbe39b7cae3a9de650d035af22dd5fb4 Mon Sep 17 00:00:00 2001 From: "Liam R. Howlett" Date: Fri, 20 Jan 2023 11:26:46 -0500 Subject: [PATCH] mm/mmap: don't use __vma_adjust() in shift_arg_pages() Introduce shrink_vma() which uses the vma_prepare() and vma_complete() functions to reduce the vma coverage. Convert shift_arg_pages() to use expand_vma() and the new shrink_vma() function. Remove support from __vma_adjust() to reduce a vma size since shift_arg_pages() is the only user that shrinks a VMA in this way. Link: https://lkml.kernel.org/r/20230120162650.984577-46-Liam.Howlett@oracle.com Signed-off-by: Liam R. Howlett Signed-off-by: Andrew Morton --- fs/exec.c | 4 ++-- include/linux/mm.h | 10 ++-------- mm/mmap.c | 52 +++++++++++++++++++++++++++++++++++++++++++--------- 3 files changed, 47 insertions(+), 19 deletions(-) diff --git a/fs/exec.c b/fs/exec.c index d52fca2dd30b..c0df813d2b45 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -699,7 +699,7 @@ static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift) /* * cover the whole range: [new_start, old_end) */ - if (vma_adjust(&vmi, vma, new_start, old_end, vma->vm_pgoff)) + if (vma_expand(&vmi, vma, new_start, old_end, vma->vm_pgoff, NULL)) return -ENOMEM; /* @@ -733,7 +733,7 @@ static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift) vma_prev(&vmi); /* Shrink the vma to just the new range */ - return vma_adjust(&vmi, vma, new_start, new_end, vma->vm_pgoff); + return vma_shrink(&vmi, vma, new_start, new_end, vma->vm_pgoff); } /* diff --git a/include/linux/mm.h b/include/linux/mm.h index 245fb30858c9..dcc34533d2f6 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2831,17 +2831,11 @@ void anon_vma_interval_tree_verify(struct anon_vma_chain *node); /* mmap.c */ extern int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin); -extern int __vma_adjust(struct vma_iterator *vmi, struct vm_area_struct *vma, unsigned long start, - unsigned long end, pgoff_t pgoff, struct vm_area_struct *expand); -static inline int vma_adjust(struct vma_iterator *vmi, - struct vm_area_struct *vma, unsigned long start, unsigned long end, - pgoff_t pgoff) -{ - return __vma_adjust(vmi, vma, start, end, pgoff, NULL); -} extern 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); +extern int vma_shrink(struct vma_iterator *vmi, struct vm_area_struct *vma, + unsigned long start, unsigned long end, pgoff_t pgoff); extern struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *, struct vm_area_struct *prev, unsigned long addr, unsigned long end, unsigned long vm_flags, struct anon_vma *, diff --git a/mm/mmap.c b/mm/mmap.c index 9599db011b18..07b52acfd565 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -682,6 +682,44 @@ int vma_expand(struct vma_iterator *vmi, struct vm_area_struct *vma, nomem: return -ENOMEM; } + +/* + * vma_shrink() - Reduce an existing VMAs memory area + * @vmi: The vma iterator + * @vma: The VMA to modify + * @start: The new start + * @end: The new end + * + * Returns: 0 on success, -ENOMEM otherwise + */ +int vma_shrink(struct vma_iterator *vmi, struct vm_area_struct *vma, + unsigned long start, unsigned long end, pgoff_t pgoff) +{ + struct vma_prepare vp; + + WARN_ON((vma->vm_start != start) && (vma->vm_end != end)); + + if (vma_iter_prealloc(vmi)) + return -ENOMEM; + + init_vma_prep(&vp, vma); + vma_adjust_trans_huge(vma, start, end, 0); + vma_prepare(&vp); + + if (vma->vm_start < start) + vma_iter_clear(vmi, vma->vm_start, start); + + if (vma->vm_end > end) + vma_iter_clear(vmi, end, vma->vm_end); + + vma->vm_start = start; + vma->vm_end = end; + vma->vm_pgoff = pgoff; + vma_complete(&vp, vmi, vma->vm_mm); + validate_mm(vma->vm_mm); + return 0; +} + /* * We cannot adjust vm_start, vm_end, vm_pgoff fields of a vma that * is already present in an i_mmap tree without adjusting the tree. @@ -797,14 +835,7 @@ int __vma_adjust(struct vma_iterator *vmi, struct vm_area_struct *vma, vma_prepare(&vma_prep); - if (vma->vm_start < start) - vma_iter_clear(vmi, vma->vm_start, start); - else if (start != vma->vm_start) - vma_changed = true; - - if (vma->vm_end > end) - vma_iter_clear(vmi, end, vma->vm_end); - else if (end != vma->vm_end) + if (start < vma->vm_start || end > vma->vm_end) vma_changed = true; vma->vm_start = start; @@ -817,7 +848,10 @@ int __vma_adjust(struct vma_iterator *vmi, struct vm_area_struct *vma, if (adjust_next) { next->vm_start += adjust_next; next->vm_pgoff += adjust_next >> PAGE_SHIFT; - vma_iter_store(vmi, next); + if (adjust_next < 0) { + WARN_ON_ONCE(vma_changed); + vma_iter_store(vmi, next); + } } vma_complete(&vma_prep, vmi, mm); -- 2.11.0