pagewalk: don't look up vma if walk->hugetlb_entry is unused
[linux-2.6.git] / mm / pagewalk.c
1 #include <linux/mm.h>
2 #include <linux/highmem.h>
3 #include <linux/sched.h>
4 #include <linux/hugetlb.h>
5
6 static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
7                           struct mm_walk *walk)
8 {
9         pte_t *pte;
10         int err = 0;
11
12         pte = pte_offset_map(pmd, addr);
13         for (;;) {
14                 err = walk->pte_entry(pte, addr, addr + PAGE_SIZE, walk);
15                 if (err)
16                        break;
17                 addr += PAGE_SIZE;
18                 if (addr == end)
19                         break;
20                 pte++;
21         }
22
23         pte_unmap(pte);
24         return err;
25 }
26
27 static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
28                           struct mm_walk *walk)
29 {
30         pmd_t *pmd;
31         unsigned long next;
32         int err = 0;
33
34         pmd = pmd_offset(pud, addr);
35         do {
36 again:
37                 next = pmd_addr_end(addr, end);
38                 if (pmd_none(*pmd)) {
39                         if (walk->pte_hole)
40                                 err = walk->pte_hole(addr, next, walk);
41                         if (err)
42                                 break;
43                         continue;
44                 }
45                 /*
46                  * This implies that each ->pmd_entry() handler
47                  * needs to know about pmd_trans_huge() pmds
48                  */
49                 if (walk->pmd_entry)
50                         err = walk->pmd_entry(pmd, addr, next, walk);
51                 if (err)
52                         break;
53
54                 /*
55                  * Check this here so we only break down trans_huge
56                  * pages when we _need_ to
57                  */
58                 if (!walk->pte_entry)
59                         continue;
60
61                 split_huge_page_pmd(walk->mm, pmd);
62                 if (pmd_none_or_clear_bad(pmd))
63                         goto again;
64                 err = walk_pte_range(pmd, addr, next, walk);
65                 if (err)
66                         break;
67         } while (pmd++, addr = next, addr != end);
68
69         return err;
70 }
71
72 static int walk_pud_range(pgd_t *pgd, unsigned long addr, unsigned long end,
73                           struct mm_walk *walk)
74 {
75         pud_t *pud;
76         unsigned long next;
77         int err = 0;
78
79         pud = pud_offset(pgd, addr);
80         do {
81                 next = pud_addr_end(addr, end);
82                 if (pud_none_or_clear_bad(pud)) {
83                         if (walk->pte_hole)
84                                 err = walk->pte_hole(addr, next, walk);
85                         if (err)
86                                 break;
87                         continue;
88                 }
89                 if (walk->pud_entry)
90                         err = walk->pud_entry(pud, addr, next, walk);
91                 if (!err && (walk->pmd_entry || walk->pte_entry))
92                         err = walk_pmd_range(pud, addr, next, walk);
93                 if (err)
94                         break;
95         } while (pud++, addr = next, addr != end);
96
97         return err;
98 }
99
100 #ifdef CONFIG_HUGETLB_PAGE
101 static unsigned long hugetlb_entry_end(struct hstate *h, unsigned long addr,
102                                        unsigned long end)
103 {
104         unsigned long boundary = (addr & huge_page_mask(h)) + huge_page_size(h);
105         return boundary < end ? boundary : end;
106 }
107
108 static int walk_hugetlb_range(struct vm_area_struct *vma,
109                               unsigned long addr, unsigned long end,
110                               struct mm_walk *walk)
111 {
112         struct hstate *h = hstate_vma(vma);
113         unsigned long next;
114         unsigned long hmask = huge_page_mask(h);
115         pte_t *pte;
116         int err = 0;
117
118         do {
119                 next = hugetlb_entry_end(h, addr, end);
120                 pte = huge_pte_offset(walk->mm, addr & hmask);
121                 if (pte && walk->hugetlb_entry)
122                         err = walk->hugetlb_entry(pte, hmask, addr, next, walk);
123                 if (err)
124                         return err;
125         } while (addr = next, addr != end);
126
127         return 0;
128 }
129
130 static struct vm_area_struct* hugetlb_vma(unsigned long addr, struct mm_walk *walk)
131 {
132         struct vm_area_struct *vma;
133
134         /* We don't need vma lookup at all. */
135         if (!walk->hugetlb_entry)
136                 return NULL;
137
138         VM_BUG_ON(!rwsem_is_locked(&walk->mm->mmap_sem));
139         vma = find_vma(walk->mm, addr);
140         if (vma && vma->vm_start <= addr && is_vm_hugetlb_page(vma))
141                 return vma;
142
143         return NULL;
144 }
145
146 #else /* CONFIG_HUGETLB_PAGE */
147 static struct vm_area_struct* hugetlb_vma(unsigned long addr, struct mm_walk *walk)
148 {
149         return NULL;
150 }
151
152 static int walk_hugetlb_range(struct vm_area_struct *vma,
153                               unsigned long addr, unsigned long end,
154                               struct mm_walk *walk)
155 {
156         return 0;
157 }
158
159 #endif /* CONFIG_HUGETLB_PAGE */
160
161
162
163 /**
164  * walk_page_range - walk a memory map's page tables with a callback
165  * @mm: memory map to walk
166  * @addr: starting address
167  * @end: ending address
168  * @walk: set of callbacks to invoke for each level of the tree
169  *
170  * Recursively walk the page table for the memory area in a VMA,
171  * calling supplied callbacks. Callbacks are called in-order (first
172  * PGD, first PUD, first PMD, first PTE, second PTE... second PMD,
173  * etc.). If lower-level callbacks are omitted, walking depth is reduced.
174  *
175  * Each callback receives an entry pointer and the start and end of the
176  * associated range, and a copy of the original mm_walk for access to
177  * the ->private or ->mm fields.
178  *
179  * No locks are taken, but the bottom level iterator will map PTE
180  * directories from highmem if necessary.
181  *
182  * If any callback returns a non-zero value, the walk is aborted and
183  * the return value is propagated back to the caller. Otherwise 0 is returned.
184  */
185 int walk_page_range(unsigned long addr, unsigned long end,
186                     struct mm_walk *walk)
187 {
188         pgd_t *pgd;
189         unsigned long next;
190         int err = 0;
191
192         if (addr >= end)
193                 return err;
194
195         if (!walk->mm)
196                 return -EINVAL;
197
198         pgd = pgd_offset(walk->mm, addr);
199         do {
200                 struct vm_area_struct *vma;
201
202                 next = pgd_addr_end(addr, end);
203
204                 /*
205                  * handle hugetlb vma individually because pagetable walk for
206                  * the hugetlb page is dependent on the architecture and
207                  * we can't handled it in the same manner as non-huge pages.
208                  */
209                 vma = hugetlb_vma(addr, walk);
210                 if (vma) {
211                         if (vma->vm_end < next)
212                                 next = vma->vm_end;
213                         /*
214                          * Hugepage is very tightly coupled with vma, so
215                          * walk through hugetlb entries within a given vma.
216                          */
217                         err = walk_hugetlb_range(vma, addr, next, walk);
218                         if (err)
219                                 break;
220                         pgd = pgd_offset(walk->mm, next);
221                         continue;
222                 }
223
224                 if (pgd_none_or_clear_bad(pgd)) {
225                         if (walk->pte_hole)
226                                 err = walk->pte_hole(addr, next, walk);
227                         if (err)
228                                 break;
229                         pgd++;
230                         continue;
231                 }
232                 if (walk->pgd_entry)
233                         err = walk->pgd_entry(pgd, addr, next, walk);
234                 if (!err &&
235                     (walk->pud_entry || walk->pmd_entry || walk->pte_entry))
236                         err = walk_pud_range(pgd, addr, next, walk);
237                 if (err)
238                         break;
239                 pgd++;
240         } while (addr = next, addr != end);
241
242         return err;
243 }