From e495e1158da66f855646fd379e96bfd06203b367 Mon Sep 17 00:00:00 2001
From: "Liam R. Howlett" <Liam.Howlett@Oracle.com>
Date: Thu, 11 Mar 2021 15:25:33 -0500
Subject: [PATCH] mm: Move mas locking outside of munmap() path.
Now that there is a split variant that allows splitting to use a maple state,
move the locks to a more logical position.
Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
---
mm/internal.h | 4 ---
mm/mmap.c | 85 +++++++++++++++++++++++++++++++++------------------
mm/nommu.c | 4 +++
3 files changed, 60 insertions(+), 33 deletions(-)
diff --git a/mm/internal.h b/mm/internal.h
index f26ef82f3a7b..e7a526438814 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -369,9 +369,7 @@ static inline int vma_mas_store(struct vm_area_struct *vma, struct ma_state *mas
mas->index = vma->vm_start;
mas->last = vma->vm_end - 1;
- mas_lock(mas);
ret = mas_store_gfp(mas, vma, GFP_KERNEL);
- mas_unlock(mas);
return ret;
}
@@ -390,9 +388,7 @@ static inline int vma_mas_remove(struct vm_area_struct *vma, struct ma_state *ma
mas->index = vma->vm_start;
mas->last = vma->vm_end - 1;
- mas_lock(mas);
ret = mas_store_gfp(mas, NULL, GFP_KERNEL);
- mas_unlock(mas);
return ret;
}
diff --git a/mm/mmap.c b/mm/mmap.c
index db89c4b8a54d..1ae46cca1fd5 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -203,6 +203,7 @@ SYSCALL_DEFINE1(brk, unsigned long, brk)
if (mmap_write_lock_killable(mm))
return -EINTR;
+ mas_lock(&mas);
origbrk = mm->brk;
@@ -289,19 +290,21 @@ SYSCALL_DEFINE1(brk, unsigned long, brk)
goto out;
mm->brk = brk;
-
success:
populate = newbrk > oldbrk && (mm->def_flags & VM_LOCKED) != 0;
if (downgraded)
mmap_read_unlock(mm);
- else
+ else {
+ mas_unlock(&mas);
mmap_write_unlock(mm);
+ }
userfaultfd_unmap_complete(mm, &uf);
if (populate)
mm_populate(oldbrk, newbrk - oldbrk);
return brk;
out:
+ mas_unlock(&mas);
mmap_write_unlock(mm);
return origbrk;
}
@@ -503,7 +506,9 @@ static void vma_link(struct mm_struct *mm, struct vm_area_struct *vma)
{
MA_STATE(mas, &mm->mm_mt, vma->vm_start, vma->vm_end - 1);
+ mas_lock(&mas);
vma_mas_link(mm, vma, &mas);
+ mas_unlock(&mas);
}
/*
@@ -2443,8 +2448,6 @@ static inline void detach_range(struct mm_struct *mm, struct ma_state *mas,
do {
count++;
*vma = mas_prev(mas, start);
- BUG_ON((*vma)->vm_start < start);
- BUG_ON((*vma)->vm_end > end + 1);
vma_mas_store(*vma, dst);
if ((*vma)->vm_flags & VM_LOCKED) {
mm->locked_vm -= vma_pages(*vma);
@@ -2549,14 +2552,12 @@ static int do_mas_align_munmap(struct ma_state *mas, struct vm_area_struct *vma,
}
/* Point of no return */
- mas_lock(mas);
if (next)
max = next->vm_start;
mtree_init(&mt_detach, MAPLE_ALLOC_RANGE);
dst.tree = &mt_detach;
detach_range(mm, mas, &dst, &vma);
- mas_unlock(mas);
/*
* Do not downgrade mmap_lock if we are next to VM_GROWSDOWN or
@@ -2568,8 +2569,10 @@ static int do_mas_align_munmap(struct ma_state *mas, struct vm_area_struct *vma,
downgrade = false;
else if (prev && (prev->vm_flags & VM_GROWSUP))
downgrade = false;
- else
+ else {
+ mas_unlock(mas);
mmap_write_downgrade(mm);
+ }
}
/* Unmap the region */
@@ -2598,6 +2601,10 @@ static int do_mas_align_munmap(struct ma_state *mas, struct vm_area_struct *vma,
* This function takes a @mas that is in the correct state to remove the
* mapping(s). The @len will be aligned and any arch_unmap work will be
* preformed.
+ * Note: May unlock mas if lock is degraded.
+ *
+ * Returns: -EINVAL on failure, 1 on success and unlock, 0 otherwise.
+ *
*/
int do_mas_munmap(struct ma_state *mas, struct mm_struct *mm,
unsigned long start, size_t len, struct list_head *uf,
@@ -2635,7 +2642,9 @@ int do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
int ret;
MA_STATE(mas, &mm->mm_mt, start, start);
+ mas_lock(&mas);
ret = do_mas_munmap(&mas, mm, start, len, uf, false);
+ mas_unlock(&mas);
return ret;
}
@@ -2652,11 +2661,12 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
unsigned long merge_start = addr, merge_end = end;
unsigned long max = USER_PGTABLES_CEILING;
pgoff_t vm_pgoff;
- int error;
+ int error = ENOMEM;
struct ma_state ma_prev, tmp;
MA_STATE(mas, &mm->mm_mt, addr, end - 1);
+ mas_lock(&mas);
/* Check against address space limit. */
if (!may_expand_vm(mm, vm_flags, len >> PAGE_SHIFT)) {
unsigned long nr_pages;
@@ -2669,23 +2679,21 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
if (!may_expand_vm(mm, vm_flags,
(len >> PAGE_SHIFT) - nr_pages))
- return -ENOMEM;
+ goto no_mem;
}
validate_mm(mm);
/* Unmap any existing mapping in the area */
- if (do_mas_munmap(&mas, mm, addr, len, uf, false)) {
- return -ENOMEM;
- }
+ if (do_mas_munmap(&mas, mm, addr, len, uf, false))
+ goto no_mem;
/*
* Private writable mapping: check memory availability
*/
if (accountable_mapping(file, vm_flags)) {
charged = len >> PAGE_SHIFT;
- if (security_vm_enough_memory_mm(mm, charged)) {
- return -ENOMEM;
- }
+ if (security_vm_enough_memory_mm(mm, charged))
+ goto no_mem;
vm_flags |= VM_ACCOUNT;
}
@@ -2736,10 +2744,8 @@ cannot_expand:
* not unmapped, but the maps are removed from the list.
*/
vma = vm_area_alloc(mm);
- if (!vma) {
- error = -ENOMEM;
+ if (!vma)
goto unacct_error;
- }
vma->vm_start = addr;
vma->vm_end = end;
@@ -2864,6 +2870,7 @@ expanded:
vma->vm_flags |= VM_SOFTDIRTY;
vma_set_page_prot(vma);
validate_mm(mm);
+ mas_unlock(&mas);
return addr;
unmap_and_free_vma:
@@ -2884,6 +2891,8 @@ free_vma:
unacct_error:
if (charged)
vm_unacct_memory(charged);
+no_mem:
+ mas_unlock(&mas);
return error;
}
@@ -2896,6 +2905,7 @@ static int __vm_munmap(unsigned long start, size_t len, bool downgrade)
if (mmap_write_lock_killable(mm))
return -EINTR;
+ mas_lock(&mas);
ret = do_mas_munmap(&mas, mm, start, len, &uf, downgrade);
/*
* Returning 1 indicates mmap_lock is downgraded.
@@ -2905,8 +2915,10 @@ static int __vm_munmap(unsigned long start, size_t len, bool downgrade)
if (ret == 1) {
mmap_read_unlock(mm);
ret = 0;
- } else
+ } else {
+ mas_unlock(&mas);
mmap_write_unlock(mm);
+ }
userfaultfd_unmap_complete(mm, &uf);
return ret;
@@ -2958,6 +2970,7 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
if (mmap_write_lock_killable(mm))
return -EINTR;
+ rcu_read_lock();
mas_set(&mas, start);
vma = mas_walk(&mas);
@@ -3006,6 +3019,7 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
prot, flags, pgoff, &populate, NULL);
fput(file);
out:
+ rcu_read_unlock();
mmap_write_unlock(mm);
if (populate)
mm_populate(ret, populate);
@@ -3022,7 +3036,8 @@ out:
* @oldbrk: The end of the address to unmap
* @uf: The userfaultfd list_head
*
- * Returns: 0 on success.
+ * Returns: 0 on success, 1 on success and downgraded write lock, negative
+ * otherwise.
* unmaps a partial VMA mapping. Does not handle alignment, downgrades lock if
* possible.
*/
@@ -3084,6 +3099,7 @@ static int do_brk_munmap(struct ma_state *mas, struct vm_area_struct *vma,
munlock_vma_pages_range(&unmap, newbrk, oldbrk);
}
+ mas_unlock(mas);
mmap_write_downgrade(mm);
unmap_region(mm, &unmap, mas, newbrk, oldbrk, vma,
next ? next->vm_start : 0);
@@ -3166,13 +3182,10 @@ static int do_brk_flags(struct ma_state *mas, struct ma_state *ma_prev,
anon_vma_lock_write(vma->anon_vma);
anon_vma_interval_tree_pre_update_vma(vma);
}
- mas_lock(ma_prev);
vma->vm_end = addr + len;
vma->vm_flags |= VM_SOFTDIRTY;
- if (mas_store_gfp(ma_prev, vma, GFP_KERNEL)) {
- mas_unlock(ma_prev);
+ if (mas_store_gfp(ma_prev, vma, GFP_KERNEL))
goto mas_mod_fail;
- }
if (vma->anon_vma) {
anon_vma_interval_tree_post_update_vma(vma);
@@ -3243,10 +3256,12 @@ int vm_brk_flags(unsigned long addr, unsigned long request, unsigned long flags)
if (mmap_write_lock_killable(mm))
return -EINTR;
+ mas_lock(&mas);
// This vma left intentionally blank.
mas_walk(&mas);
ret = do_brk_flags(&mas, &mas, &vma, addr, len, flags);
populate = ((mm->def_flags & VM_LOCKED) != 0);
+ mas_unlock(&mas);
mmap_write_unlock(mm);
if (populate && !ret)
mm_populate(addr, len);
@@ -3308,9 +3323,10 @@ void exit_mmap(struct mm_struct *mm)
arch_exit_mmap(mm);
+ mas_lock(&mas);
vma = mas_find(&mas, ULONG_MAX);
if (!vma) { /* Can happen if dup_mmap() received an OOM */
- rcu_read_unlock();
+ mas_unlock(&mas);
return;
}
@@ -3323,6 +3339,7 @@ void exit_mmap(struct mm_struct *mm)
unmap_vmas(&tlb, vma, &mas, 0, -1);
free_pgtables(&tlb, &mas2, vma, FIRST_USER_ADDRESS, USER_PGTABLES_CEILING);
tlb_finish_mmu(&tlb);
+ mas_unlock(&mas);
/*
* Walk the list again, actually closing and freeing it,
@@ -3347,12 +3364,16 @@ void exit_mmap(struct mm_struct *mm)
*/
int insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
{
- if (find_vma_intersection(mm, vma->vm_start, vma->vm_end))
- return -ENOMEM;
+ MA_STATE(mas, &mm->mm_mt, vma->vm_start, vma->vm_end - 1);
+
+ mas_lock(&mas);
+ if (mas_find(&mas, vma->vm_end - 1))
+ goto no_mem;
if ((vma->vm_flags & VM_ACCOUNT) &&
security_vm_enough_memory_mm(mm, vma_pages(vma)))
- return -ENOMEM;
+ goto no_mem;
+
/*
* The vm_pgoff of a purely anonymous vma should be irrelevant
@@ -3371,8 +3392,14 @@ int insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
vma->vm_pgoff = vma->vm_start >> PAGE_SHIFT;
}
- vma_link(mm, vma);
+ mas_reset(&mas);
+ vma_mas_link(mm, vma, &mas);
+ mas_unlock(&mas);
return 0;
+
+no_mem:
+ mas_unlock(&mas);
+ return -ENOMEM;
}
/*
diff --git a/mm/nommu.c b/mm/nommu.c
index fa1e387c2a33..46dbdd4050a0 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -571,6 +571,7 @@ static void add_vma_to_mm(struct mm_struct *mm, struct vm_area_struct *vma)
BUG_ON(!vma->vm_region);
+ mas_lock(&mas);
mm->map_count++;
printk("mm at %u\n", mm->map_count);
vma->vm_mm = mm;
@@ -592,6 +593,7 @@ static void add_vma_to_mm(struct mm_struct *mm, struct vm_area_struct *vma)
mas_reset(&mas);
/* add the VMA to the tree */
vma_mas_store(vma, &mas);
+ mas_unlock(&mas);
}
/*
@@ -601,6 +603,7 @@ static void delete_vma_from_mm(struct vm_area_struct *vma)
{
MA_STATE(mas, &vma->vm_mm->mm_mt, 0, 0);
+ mas_lock(&mas);
vma->vm_mm->map_count--;
/* remove the VMA from the mapping */
if (vma->vm_file) {
@@ -616,6 +619,7 @@ static void delete_vma_from_mm(struct vm_area_struct *vma)
/* remove from the MM's tree and list */
vma_mas_remove(vma, &mas);
+ mas_unlock(&mas);
}
/*
--
2.50.1