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mm: rcu safe VMA freeing 

This prepares for page faults handling under VMA lock, looking up VMAs
under protection of an rcu read lock, instead of the usual mmap read lock.

Link: https://lkml.kernel.org/r/20230227173632.3292573-11-surenb@google.com
Signed-off-by: Michel Lespinasse <michel@lespinasse.org>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Michel Lespinasse 2023-02-27 09:36:09 -08:00 committed by Andrew Morton
parent 0b6cc04f3d
commit 20cce633f4
2 changed files with 29 additions and 4 deletions
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13
include/linux/mm_types.h
View File

@ -480,9 +480,16 @@ struct anon_vma_name {
struct vm_area_struct {
/* The first cache line has the info for VMA tree walking. */
unsigned long vm_start; /* Our start address within vm_mm. */
unsigned long vm_end; /* The first byte after our end address
within vm_mm. */
union {
struct {
/* VMA covers [vm_start; vm_end) addresses within mm */
unsigned long vm_start;
unsigned long vm_end;
};
#ifdef CONFIG_PER_VMA_LOCK
struct rcu_head vm_rcu; /* Used for deferred freeing. */
#endif
};
struct mm_struct *vm_mm; /* The address space we belong to. */
pgprot_t vm_page_prot; /* Access permissions of this VMA. */

20
kernel/fork.c
View File

@ -479,12 +479,30 @@ struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
return new;
}
void vm_area_free(struct vm_area_struct *vma)
static void __vm_area_free(struct vm_area_struct *vma)
{
free_anon_vma_name(vma);
kmem_cache_free(vm_area_cachep, vma);
}
#ifdef CONFIG_PER_VMA_LOCK
static void vm_area_free_rcu_cb(struct rcu_head *head)
{
struct vm_area_struct *vma = container_of(head, struct vm_area_struct,
vm_rcu);
__vm_area_free(vma);
}
#endif
void vm_area_free(struct vm_area_struct *vma)
{
#ifdef CONFIG_PER_VMA_LOCK
call_rcu(&vma->vm_rcu, vm_area_free_rcu_cb);
#else
__vm_area_free(vma);
#endif
}
static void account_kernel_stack(struct task_struct *tsk, int account)
{
if (IS_ENABLED(CONFIG_VMAP_STACK)) {