[PATCH] mm: add a new function (needed for swap suspend)

This adds the function get_swap_page_of_type() allowing us to specify an index
in swap_info[] and select a swap_info_struct structure to be used for
allocating a swap page.

This function (or another one of similar functionality) will be necessary for
implementing the image-writing part of swsusp in the user space.   It can also
be used for simplifying the current in-kernel implementation of the
image-writing part of swsusp.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/include/linux/swap.h b/include/linux/swap.h
index bd6641784107620c6263b4779bd1e5379e3659fb..556617bcf7accb79a763eda248e4075df6330e1a 100644 (file)
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -209,6 +209,7 @@ extern unsigned int nr_swapfiles;
 extern struct swap_info_struct swap_info[];
 extern void si_swapinfo(struct sysinfo *);
 extern swp_entry_t get_swap_page(void);
+extern swp_entry_t get_swap_page_of_type(int type);
 extern int swap_duplicate(swp_entry_t);
 extern int valid_swaphandles(swp_entry_t, unsigned long *);
 extern void swap_free(swp_entry_t);

diff --git a/mm/swapfile.c b/mm/swapfile.c
index edafeace301f01879e04d31c9bf9e5c01a4484e9..6da4b28b896b311f681069a3ef45ffec358d4b11 100644 (file)
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -211,6 +211,26 @@ noswap:
        return (swp_entry_t) {0};
 }
 
+swp_entry_t get_swap_page_of_type(int type)
+{
+       struct swap_info_struct *si;
+       pgoff_t offset;
+
+       spin_lock(&swap_lock);
+       si = swap_info + type;
+       if (si->flags & SWP_WRITEOK) {
+               nr_swap_pages--;
+               offset = scan_swap_map(si);
+               if (offset) {
+                       spin_unlock(&swap_lock);
+                       return swp_entry(type, offset);
+               }
+               nr_swap_pages++;
+       }
+       spin_unlock(&swap_lock);
+       return (swp_entry_t) {0};
+}
+
 static struct swap_info_struct * swap_info_get(swp_entry_t entry)
 {
        struct swap_info_struct * p;