2 * Copyright (c) 2006 Oracle. All rights reserved.
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6 * General Public License (GPL) Version 2, available from the file
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23 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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29 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
33 #include <linux/highmem.h>
37 struct rds_page_remainder {
39 unsigned long r_offset;
42 DEFINE_PER_CPU_SHARED_ALIGNED(struct rds_page_remainder, rds_page_remainders);
45 * returns 0 on success or -errno on failure.
47 * We don't have to worry about flush_dcache_page() as this only works
48 * with private pages. If, say, we were to do directed receive to pinned
49 * user pages we'd have to worry more about cache coherence. (Though
50 * the flush_dcache_page() in get_user_pages() would probably be enough).
52 int rds_page_copy_user(struct page *page, unsigned long offset,
53 void __user *ptr, unsigned long bytes,
61 rds_stats_add(s_copy_to_user, bytes);
62 ret = copy_to_user(ptr, addr + offset, bytes);
64 rds_stats_add(s_copy_from_user, bytes);
65 ret = copy_from_user(addr + offset, ptr, bytes);
69 return ret ? -EFAULT : 0;
71 EXPORT_SYMBOL_GPL(rds_page_copy_user);
74 * Message allocation uses this to build up regions of a message.
76 * @bytes - the number of bytes needed.
77 * @gfp - the waiting behaviour of the allocation
79 * @gfp is always ored with __GFP_HIGHMEM. Callers must be prepared to
80 * kmap the pages, etc.
82 * If @bytes is at least a full page then this just returns a page from
85 * If @bytes is a partial page then this stores the unused region of the
86 * page in a per-cpu structure. Future partial-page allocations may be
87 * satisfied from that cached region. This lets us waste less memory on
88 * small allocations with minimal complexity. It works because the transmit
89 * path passes read-only page regions down to devices. They hold a page
90 * reference until they are done with the region.
92 int rds_page_remainder_alloc(struct scatterlist *scat, unsigned long bytes,
95 struct rds_page_remainder *rem;
100 gfp |= __GFP_HIGHMEM;
102 /* jump straight to allocation if we're trying for a huge page */
103 if (bytes >= PAGE_SIZE) {
104 page = alloc_page(gfp);
108 sg_set_page(scat, page, PAGE_SIZE, 0);
114 rem = &per_cpu(rds_page_remainders, get_cpu());
115 local_irq_save(flags);
118 /* avoid a tiny region getting stuck by tossing it */
119 if (rem->r_page && bytes > (PAGE_SIZE - rem->r_offset)) {
120 rds_stats_inc(s_page_remainder_miss);
121 __free_page(rem->r_page);
125 /* hand out a fragment from the cached page */
126 if (rem->r_page && bytes <= (PAGE_SIZE - rem->r_offset)) {
127 sg_set_page(scat, rem->r_page, bytes, rem->r_offset);
128 get_page(sg_page(scat));
130 if (rem->r_offset != 0)
131 rds_stats_inc(s_page_remainder_hit);
133 rem->r_offset += bytes;
134 if (rem->r_offset == PAGE_SIZE) {
135 __free_page(rem->r_page);
142 /* alloc if there is nothing for us to use */
143 local_irq_restore(flags);
146 page = alloc_page(gfp);
148 rem = &per_cpu(rds_page_remainders, get_cpu());
149 local_irq_save(flags);
156 /* did someone race to fill the remainder before us? */
162 /* otherwise install our page and loop around to alloc */
167 local_irq_restore(flags);
170 rdsdebug("bytes %lu ret %d %p %u %u\n", bytes, ret,
171 ret ? NULL : sg_page(scat), ret ? 0 : scat->offset,
172 ret ? 0 : scat->length);
176 static int rds_page_remainder_cpu_notify(struct notifier_block *self,
177 unsigned long action, void *hcpu)
179 struct rds_page_remainder *rem;
180 long cpu = (long)hcpu;
182 rem = &per_cpu(rds_page_remainders, cpu);
184 rdsdebug("cpu %ld action 0x%lx\n", cpu, action);
189 __free_page(rem->r_page);
197 static struct notifier_block rds_page_remainder_nb = {
198 .notifier_call = rds_page_remainder_cpu_notify,
201 void rds_page_exit(void)
205 for_each_possible_cpu(i)
206 rds_page_remainder_cpu_notify(&rds_page_remainder_nb,
207 (unsigned long)CPU_DEAD,