fs/erofs/pcpubuf.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) Gao Xiang <xiang@kernel.org>
   4  *
   5  * For low-latency decompression algorithms (e.g. lz4), reserve consecutive
   6  * per-CPU virtual memory (in pages) in advance to store such inplace I/O
   7  * data if inplace decompression is failed (due to unmet inplace margin for
   8  * example).
   9  */
  10 #include "internal.h"
  11
  12 struct erofs_pcpubuf {
  13         raw_spinlock_t lock;
  14         void *ptr;
  15         struct page **pages;
  16         unsigned int nrpages;
  17 };
  18
  19 static DEFINE_PER_CPU(struct erofs_pcpubuf, erofs_pcb);
  20
  21 void *erofs_get_pcpubuf(unsigned int requiredpages)
  22         __acquires(pcb->lock)
  23 {
  24         struct erofs_pcpubuf *pcb = &get_cpu_var(erofs_pcb);
  25
  26         raw_spin_lock(&pcb->lock);
  27         /* check if the per-CPU buffer is too small */
  28         if (requiredpages > pcb->nrpages) {
  29                 raw_spin_unlock(&pcb->lock);
  30                 put_cpu_var(erofs_pcb);
  31                 /* (for sparse checker) pretend pcb->lock is still taken */
  32                 __acquire(pcb->lock);
  33                 return NULL;
  34         }
  35         return pcb->ptr;
  36 }
  37
  38 void erofs_put_pcpubuf(void *ptr) __releases(pcb->lock)
  39 {
  40         struct erofs_pcpubuf *pcb = &per_cpu(erofs_pcb, smp_processor_id());
  41
  42         DBG_BUGON(pcb->ptr != ptr);
  43         raw_spin_unlock(&pcb->lock);
  44         put_cpu_var(erofs_pcb);
  45 }
  46
  47 /* the next step: support per-CPU page buffers hotplug */
  48 int erofs_pcpubuf_growsize(unsigned int nrpages)
  49 {
  50         static DEFINE_MUTEX(pcb_resize_mutex);
  51         static unsigned int pcb_nrpages;
  52         LIST_HEAD(pagepool);
  53         int delta, cpu, ret, i;
  54
  55         mutex_lock(&pcb_resize_mutex);
  56         delta = nrpages - pcb_nrpages;
  57         ret = 0;
  58         /* avoid shrinking pcpubuf, since no idea how many fses rely on */
  59         if (delta <= 0)
  60                 goto out;
  61
  62         for_each_possible_cpu(cpu) {
  63                 struct erofs_pcpubuf *pcb = &per_cpu(erofs_pcb, cpu);
  64                 struct page **pages, **oldpages;
  65                 void *ptr, *old_ptr;
  66
  67                 pages = kmalloc_array(nrpages, sizeof(*pages), GFP_KERNEL);
  68                 if (!pages) {
  69                         ret = -ENOMEM;
  70                         break;
  71                 }
  72
  73                 for (i = 0; i < nrpages; ++i) {
  74                         pages[i] = erofs_allocpage(&pagepool, GFP_KERNEL);
  75                         if (!pages[i]) {
  76                                 ret = -ENOMEM;
  77                                 oldpages = pages;
  78                                 goto free_pagearray;
  79                         }
  80                 }
  81                 ptr = vmap(pages, nrpages, VM_MAP, PAGE_KERNEL);
  82                 if (!ptr) {
  83                         ret = -ENOMEM;
  84                         oldpages = pages;
  85                         goto free_pagearray;
  86                 }
  87                 raw_spin_lock(&pcb->lock);
  88                 old_ptr = pcb->ptr;
  89                 pcb->ptr = ptr;
  90                 oldpages = pcb->pages;
  91                 pcb->pages = pages;
  92                 i = pcb->nrpages;
  93                 pcb->nrpages = nrpages;
  94                 raw_spin_unlock(&pcb->lock);
  95
  96                 if (!oldpages) {
  97                         DBG_BUGON(old_ptr);
  98                         continue;
  99                 }
 100
 101                 if (old_ptr)
 102                         vunmap(old_ptr);
 103 free_pagearray:
 104                 while (i)
 105                         list_add(&oldpages[--i]->lru, &pagepool);
 106                 kfree(oldpages);
 107                 if (ret)
 108                         break;
 109         }
 110         pcb_nrpages = nrpages;
 111         put_pages_list(&pagepool);
 112 out:
 113         mutex_unlock(&pcb_resize_mutex);
 114         return ret;
 115 }
 116
 117 void erofs_pcpubuf_init(void)
 118 {
 119         int cpu;
 120
 121         for_each_possible_cpu(cpu) {
 122                 struct erofs_pcpubuf *pcb = &per_cpu(erofs_pcb, cpu);
 123
 124                 raw_spin_lock_init(&pcb->lock);
 125         }
 126 }
 127
 128 void erofs_pcpubuf_exit(void)
 129 {
 130         int cpu, i;
 131
 132         for_each_possible_cpu(cpu) {
 133                 struct erofs_pcpubuf *pcb = &per_cpu(erofs_pcb, cpu);
 134
 135                 if (pcb->ptr) {
 136                         vunmap(pcb->ptr);
 137                         pcb->ptr = NULL;
 138                 }
 139                 if (!pcb->pages)
 140                         continue;
 141
 142                 for (i = 0; i < pcb->nrpages; ++i)
 143                         if (pcb->pages[i])
 144                                 put_page(pcb->pages[i]);
 145                 kfree(pcb->pages);
 146                 pcb->pages = NULL;
 147         }
 148 }