linux/mm/vmacache.c
Christoph Hellwig f5678e7f2a kernel: better document the use_mm/unuse_mm API contract
Switch the function documentation to kerneldoc comments, and add
WARN_ON_ONCE asserts that the calling thread is a kernel thread and does
not have ->mm set (or has ->mm set in the case of unuse_mm).

Also give the functions a kthread_ prefix to better document the use case.

[hch@lst.de: fix a comment typo, cover the newly merged use_mm/unuse_mm caller in vfio]
  Link: http://lkml.kernel.org/r/20200416053158.586887-3-hch@lst.de
[sfr@canb.auug.org.au: powerpc/vas: fix up for {un}use_mm() rename]
  Link: http://lkml.kernel.org/r/20200422163935.5aa93ba5@canb.auug.org.au

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: Jens Axboe <axboe@kernel.dk>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Felix Kuehling <Felix.Kuehling@amd.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> [usb]
Acked-by: Haren Myneni <haren@linux.ibm.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Felipe Balbi <balbi@kernel.org>
Cc: Jason Wang <jasowang@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
Cc: Zhi Wang <zhi.a.wang@intel.com>
Link: http://lkml.kernel.org/r/20200404094101.672954-6-hch@lst.de
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-06-10 19:14:18 -07:00

118 lines
2.7 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2014 Davidlohr Bueso.
*/
#include <linux/sched/signal.h>
#include <linux/sched/task.h>
#include <linux/mm.h>
#include <linux/vmacache.h>
/*
* Hash based on the pmd of addr if configured with MMU, which provides a good
* hit rate for workloads with spatial locality. Otherwise, use pages.
*/
#ifdef CONFIG_MMU
#define VMACACHE_SHIFT PMD_SHIFT
#else
#define VMACACHE_SHIFT PAGE_SHIFT
#endif
#define VMACACHE_HASH(addr) ((addr >> VMACACHE_SHIFT) & VMACACHE_MASK)
/*
* This task may be accessing a foreign mm via (for example)
* get_user_pages()->find_vma(). The vmacache is task-local and this
* task's vmacache pertains to a different mm (ie, its own). There is
* nothing we can do here.
*
* Also handle the case where a kernel thread has adopted this mm via
* kthread_use_mm(). That kernel thread's vmacache is not applicable to this mm.
*/
static inline bool vmacache_valid_mm(struct mm_struct *mm)
{
return current->mm == mm && !(current->flags & PF_KTHREAD);
}
void vmacache_update(unsigned long addr, struct vm_area_struct *newvma)
{
if (vmacache_valid_mm(newvma->vm_mm))
current->vmacache.vmas[VMACACHE_HASH(addr)] = newvma;
}
static bool vmacache_valid(struct mm_struct *mm)
{
struct task_struct *curr;
if (!vmacache_valid_mm(mm))
return false;
curr = current;
if (mm->vmacache_seqnum != curr->vmacache.seqnum) {
/*
* First attempt will always be invalid, initialize
* the new cache for this task here.
*/
curr->vmacache.seqnum = mm->vmacache_seqnum;
vmacache_flush(curr);
return false;
}
return true;
}
struct vm_area_struct *vmacache_find(struct mm_struct *mm, unsigned long addr)
{
int idx = VMACACHE_HASH(addr);
int i;
count_vm_vmacache_event(VMACACHE_FIND_CALLS);
if (!vmacache_valid(mm))
return NULL;
for (i = 0; i < VMACACHE_SIZE; i++) {
struct vm_area_struct *vma = current->vmacache.vmas[idx];
if (vma) {
#ifdef CONFIG_DEBUG_VM_VMACACHE
if (WARN_ON_ONCE(vma->vm_mm != mm))
break;
#endif
if (vma->vm_start <= addr && vma->vm_end > addr) {
count_vm_vmacache_event(VMACACHE_FIND_HITS);
return vma;
}
}
if (++idx == VMACACHE_SIZE)
idx = 0;
}
return NULL;
}
#ifndef CONFIG_MMU
struct vm_area_struct *vmacache_find_exact(struct mm_struct *mm,
unsigned long start,
unsigned long end)
{
int idx = VMACACHE_HASH(start);
int i;
count_vm_vmacache_event(VMACACHE_FIND_CALLS);
if (!vmacache_valid(mm))
return NULL;
for (i = 0; i < VMACACHE_SIZE; i++) {
struct vm_area_struct *vma = current->vmacache.vmas[idx];
if (vma && vma->vm_start == start && vma->vm_end == end) {
count_vm_vmacache_event(VMACACHE_FIND_HITS);
return vma;
}
if (++idx == VMACACHE_SIZE)
idx = 0;
}
return NULL;
}
#endif