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>

diff --git a/mm/internal.h b/mm/internal.h
index f26ef82f3a7b2bf6faeee9a0fc23d7875283e291..e7a526438814fa2a3ecc68f5d5cc84c0b7595a3d 100644 (file)
--- 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 db89c4b8a54d526672f2d881cb983114cfeace91..1ae46cca1fd565f96ee897382390ed77f36f7da1 100644 (file)
--- 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 fa1e387c2a33c1832076089fef2bb96d087728d6..46dbdd4050a013fa6b51e1c1ad079d33f30b3268 100644 (file)
--- 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);
 }
 
 /*