[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>

2 files changed, 21 insertions, 0 deletions

diff --git a/include/linux/swap.h b/include/linux/swap.h
index bd6641784107..556617bcf7ac 100644
--- 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 edafeace301f..6da4b28b896b 100644
--- 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;