include/linux/sched/mm.h

   1 #ifndef _LINUX_SCHED_MM_H
   2 #define _LINUX_SCHED_MM_H
   3
   4 #include <linux/kernel.h>
   5 #include <linux/atomic.h>
   6 #include <linux/sched.h>
   7 #include <linux/mm_types.h>
   8 #include <linux/gfp.h>
   9
  10 /*
  11  * Routines for handling mm_structs
  12  */
  13 extern struct mm_struct * mm_alloc(void);
  14
  15 /**
  16  * mmgrab() - Pin a &struct mm_struct.
  17  * @mm: The &struct mm_struct to pin.
  18  *
  19  * Make sure that @mm will not get freed even after the owning task
  20  * exits. This doesn't guarantee that the associated address space
  21  * will still exist later on and mmget_not_zero() has to be used before
  22  * accessing it.
  23  *
  24  * This is a preferred way to to pin @mm for a longer/unbounded amount
  25  * of time.
  26  *
  27  * Use mmdrop() to release the reference acquired by mmgrab().
  28  *
  29  * See also <Documentation/vm/active_mm.txt> for an in-depth explanation
  30  * of &mm_struct.mm_count vs &mm_struct.mm_users.
  31  */
  32 static inline void mmgrab(struct mm_struct *mm)
  33 {
  34         atomic_inc(&mm->mm_count);
  35 }
  36
  37 /* mmdrop drops the mm and the page tables */
  38 extern void __mmdrop(struct mm_struct *);
  39 static inline void mmdrop(struct mm_struct *mm)
  40 {
  41         if (unlikely(atomic_dec_and_test(&mm->mm_count)))
  42                 __mmdrop(mm);
  43 }
  44
  45 static inline void mmdrop_async_fn(struct work_struct *work)
  46 {
  47         struct mm_struct *mm = container_of(work, struct mm_struct, async_put_work);
  48         __mmdrop(mm);
  49 }
  50
  51 static inline void mmdrop_async(struct mm_struct *mm)
  52 {
  53         if (unlikely(atomic_dec_and_test(&mm->mm_count))) {
  54                 INIT_WORK(&mm->async_put_work, mmdrop_async_fn);
  55                 schedule_work(&mm->async_put_work);
  56         }
  57 }
  58
  59 /**
  60  * mmget() - Pin the address space associated with a &struct mm_struct.
  61  * @mm: The address space to pin.
  62  *
  63  * Make sure that the address space of the given &struct mm_struct doesn't
  64  * go away. This does not protect against parts of the address space being
  65  * modified or freed, however.
  66  *
  67  * Never use this function to pin this address space for an
  68  * unbounded/indefinite amount of time.
  69  *
  70  * Use mmput() to release the reference acquired by mmget().
  71  *
  72  * See also <Documentation/vm/active_mm.txt> for an in-depth explanation
  73  * of &mm_struct.mm_count vs &mm_struct.mm_users.
  74  */
  75 static inline void mmget(struct mm_struct *mm)
  76 {
  77         atomic_inc(&mm->mm_users);
  78 }
  79
  80 static inline bool mmget_not_zero(struct mm_struct *mm)
  81 {
  82         return atomic_inc_not_zero(&mm->mm_users);
  83 }
  84
  85 /* mmput gets rid of the mappings and all user-space */
  86 extern void mmput(struct mm_struct *);
  87 #ifdef CONFIG_MMU
  88 /* same as above but performs the slow path from the async context. Can
  89  * be called from the atomic context as well
  90  */
  91 extern void mmput_async(struct mm_struct *);
  92 #endif
  93
  94 /* Grab a reference to a task's mm, if it is not already going away */
  95 extern struct mm_struct *get_task_mm(struct task_struct *task);
  96 /*
  97  * Grab a reference to a task's mm, if it is not already going away
  98  * and ptrace_may_access with the mode parameter passed to it
  99  * succeeds.
 100  */
 101 extern struct mm_struct *mm_access(struct task_struct *task, unsigned int mode);
 102 /* Remove the current tasks stale references to the old mm_struct */
 103 extern void mm_release(struct task_struct *, struct mm_struct *);
 104
 105 #ifdef CONFIG_MEMCG
 106 extern void mm_update_next_owner(struct mm_struct *mm);
 107 #else
 108 static inline void mm_update_next_owner(struct mm_struct *mm)
 109 {
 110 }
 111 #endif /* CONFIG_MEMCG */
 112
 113 #ifdef CONFIG_MMU
 114 extern void arch_pick_mmap_layout(struct mm_struct *mm);
 115 extern unsigned long
 116 arch_get_unmapped_area(struct file *, unsigned long, unsigned long,
 117                        unsigned long, unsigned long);
 118 extern unsigned long
 119 arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
 120                           unsigned long len, unsigned long pgoff,
 121                           unsigned long flags);
 122 #else
 123 static inline void arch_pick_mmap_layout(struct mm_struct *mm) {}
 124 #endif
 125
 126 static inline bool in_vfork(struct task_struct *tsk)
 127 {
 128         bool ret;
 129
 130         /*
 131          * need RCU to access ->real_parent if CLONE_VM was used along with
 132          * CLONE_PARENT.
 133          *
 134          * We check real_parent->mm == tsk->mm because CLONE_VFORK does not
 135          * imply CLONE_VM
 136          *
 137          * CLONE_VFORK can be used with CLONE_PARENT/CLONE_THREAD and thus
 138          * ->real_parent is not necessarily the task doing vfork(), so in
 139          * theory we can't rely on task_lock() if we want to dereference it.
 140          *
 141          * And in this case we can't trust the real_parent->mm == tsk->mm
 142          * check, it can be false negative. But we do not care, if init or
 143          * another oom-unkillable task does this it should blame itself.
 144          */
 145         rcu_read_lock();
 146         ret = tsk->vfork_done && tsk->real_parent->mm == tsk->mm;
 147         rcu_read_unlock();
 148
 149         return ret;
 150 }
 151
 152 /* __GFP_IO isn't allowed if PF_MEMALLOC_NOIO is set in current->flags
 153  * __GFP_FS is also cleared as it implies __GFP_IO.
 154  */
 155 static inline gfp_t memalloc_noio_flags(gfp_t flags)
 156 {
 157         if (unlikely(current->flags & PF_MEMALLOC_NOIO))
 158                 flags &= ~(__GFP_IO | __GFP_FS);
 159         return flags;
 160 }
 161
 162 static inline unsigned int memalloc_noio_save(void)
 163 {
 164         unsigned int flags = current->flags & PF_MEMALLOC_NOIO;
 165         current->flags |= PF_MEMALLOC_NOIO;
 166         return flags;
 167 }
 168
 169 static inline void memalloc_noio_restore(unsigned int flags)
 170 {
 171         current->flags = (current->flags & ~PF_MEMALLOC_NOIO) | flags;
 172 }
 173
 174 #endif /* _LINUX_SCHED_MM_H */