On 07/16/2010 05:13 AM, Lai Jiangshan wrote:
a light weight version of get_user_page_and_protection()
@@ -375,3 +374,83 @@ slow_irqon:
return ret;
}
}
+
+/*
+ * get a current mapped page fast, and test whether the page is writable.
+ * equivalent version(but slower):
+ * {
+ * struct page *page[1];
+ *
+ * if (__get_user_pages_fast(addr, 1, 1, page) == 1) {
+ * *writable = 1;
+ * return page[0];
+ * }
+ * if (__get_user_pages_fast(addr, 1, 0, page) == 1) {
+ * *writable = 0;
+ * return page[0];
+ * }
+ * return NULL;
+ * }
+ */
+struct page *get_user_page_and_protection(unsigned long addr, int *writable)
+{
<snip lots of code>
+}
+EXPORT_SYMBOL_GPL(get_user_page_and_protection);
+
This a duplication of __get_user_pages_fast(), no?
I think a better way is to have a __get_user_pages_ptes(..., struct page
*pages, pte_t *ptes, ...), and write __get_user_pages_fast() in terms of
that. There's lots of useful info from the pte we can use:
- writeable bit (used here)
- page size (we can stick it in some user bits, speeds up
host_mapping_level())
- dirty bit (if set, we can set it for speculative sptes and save the
CPU a RMW)
- page attribute (for device assignment, when snooping is not available)
Nick, is __get_user_pages_ptes() fine with you?
--
error compiling committee.c: too many arguments to function
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