4 files changed, 106 insertions, 88 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 38356ab827c9..c8667f8b5358 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -429,6 +429,7 @@ struct kstatfs;
 struct vm_area_struct;
 struct vfsmount;
 struct cred;
+struct swap_info_struct;
 
 extern void __init inode_init(void);
 extern void __init inode_init_early(void);
@@ -640,8 +641,9 @@ struct address_space_operations {
         int (*error_remove_page)(struct address_space *, struct page *);
 
         /* swapfile support */
-        int (*swap_activate)(struct file *file);
-        int (*swap_deactivate)(struct file *file);
+        int (*swap_activate)(struct swap_info_struct *sis, struct file *file,
+                                sector_t *span);
+        void (*swap_deactivate)(struct file *file);
 };
 
 extern const struct address_space_operations empty_aops;
diff --git a/include/linux/swap.h b/include/linux/swap.h
index ab230b1ebf61..388e70601413 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -324,6 +324,11 @@ extern int swap_writepage(struct page *page, struct writeback_control *wbc);
 extern int swap_set_page_dirty(struct page *page);
 extern void end_swap_bio_read(struct bio *bio, int err);
 
+int add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
+                unsigned long nr_pages, sector_t start_block);
+int generic_swapfile_activate(struct swap_info_struct *, struct file *,
+                sector_t *);
+
 /* linux/mm/swap_state.c */
 extern struct address_space swapper_space;
 #define total_swapcache_pages  swapper_space.nrpages
diff --git a/mm/page_io.c b/mm/page_io.c
index 307a3e795290..4a379629e31f 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -87,6 +87,98 @@ void end_swap_bio_read(struct bio *bio, int err)
         bio_put(bio);
 }
 
+int generic_swapfile_activate(struct swap_info_struct *sis,
+                                struct file *swap_file,
+                                sector_t *span)
+{
+        struct address_space *mapping = swap_file->f_mapping;
+        struct inode *inode = mapping->host;
+        unsigned blocks_per_page;
+        unsigned long page_no;
+        unsigned blkbits;
+        sector_t probe_block;
+        sector_t last_block;
+        sector_t lowest_block = -1;
+        sector_t highest_block = 0;
+        int nr_extents = 0;
+        int ret;
+
+        blkbits = inode->i_blkbits;
+        blocks_per_page = PAGE_SIZE >> blkbits;
+
+        /*
+         * Map all the blocks into the extent list.  This code doesn't try
+         * to be very smart.
+         */
+        probe_block = 0;
+        page_no = 0;
+        last_block = i_size_read(inode) >> blkbits;
+        while ((probe_block + blocks_per_page) <= last_block &&
+                        page_no < sis->max) {
+                unsigned block_in_page;
+                sector_t first_block;
+
+                first_block = bmap(inode, probe_block);
+                if (first_block == 0)
+                        goto bad_bmap;
+
+                /*
+                 * It must be PAGE_SIZE aligned on-disk
+                 */
+                if (first_block & (blocks_per_page - 1)) {
+                        probe_block++;
+                        goto reprobe;
+                }
+
+                for (block_in_page = 1; block_in_page < blocks_per_page;
+                                        block_in_page++) {
+                        sector_t block;
+
+                        block = bmap(inode, probe_block + block_in_page);
+                        if (block == 0)
+                                goto bad_bmap;
+                        if (block != first_block + block_in_page) {
+                                /* Discontiguity */
+                                probe_block++;
+                                goto reprobe;
+                        }
+                }
+
+                first_block >>= (PAGE_SHIFT - blkbits);
+                if (page_no) {  /* exclude the header page */
+                        if (first_block < lowest_block)
+                                lowest_block = first_block;
+                        if (first_block > highest_block)
+                                highest_block = first_block;
+                }
+
+                /*
+                 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
+                 */
+                ret = add_swap_extent(sis, page_no, 1, first_block);
+                if (ret < 0)
+                        goto out;
+                nr_extents += ret;
+                page_no++;
+                probe_block += blocks_per_page;
+reprobe:
+                continue;
+        }
+        ret = nr_extents;
+        *span = 1 + highest_block - lowest_block;
+        if (page_no == 0)
+                page_no = 1;    /* force Empty message */
+        sis->max = page_no;
+        sis->pages = page_no - 1;
+        sis->highest_bit = page_no - 1;
+out:
+        return ret;
+bad_bmap:
+        printk(KERN_ERR "swapon: swapfile has holes\n");
+        ret = -EINVAL;
+        goto out;
+}
+
 /*
  * We may have stale swap cache pages in memory: notice
  * them here and get rid of the unnecessary final write.
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 6ffc87602f4a..7307fc928d7b 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1345,7 +1345,7 @@ static void destroy_swap_extents(struct swap_info_struct *sis)
  *
  * This function rather assumes that it is called in ascending page order.
  */
-static int
+int
 add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
                 unsigned long nr_pages, sector_t start_block)
 {
@@ -1421,106 +1421,25 @@ static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
         struct file *swap_file = sis->swap_file;
         struct address_space *mapping = swap_file->f_mapping;
         struct inode *inode = mapping->host;
-        unsigned blocks_per_page;
-        unsigned long page_no;
-        unsigned blkbits;
-        sector_t probe_block;
-        sector_t last_block;
-        sector_t lowest_block = -1;
-        sector_t highest_block = 0;
-        int nr_extents = 0;
         int ret;
 
         if (S_ISBLK(inode->i_mode)) {
                 ret = add_swap_extent(sis, 0, sis->max, 0);
                 *span = sis->pages;
-                goto out;
+                return ret;
         }
 
         if (mapping->a_ops->swap_activate) {
-                ret = mapping->a_ops->swap_activate(swap_file);
+                ret = mapping->a_ops->swap_activate(sis, swap_file, span);
                 if (!ret) {
                         sis->flags |= SWP_FILE;
                         ret = add_swap_extent(sis, 0, sis->max, 0);
                         *span = sis->pages;
                 }
-                goto out;
+                return ret;
         }
 
-        blkbits = inode->i_blkbits;
-        blocks_per_page = PAGE_SIZE >> blkbits;
-
-        /*
-         * Map all the blocks into the extent list.  This code doesn't try
-         * to be very smart.
-         */
-        probe_block = 0;
-        page_no = 0;
-        last_block = i_size_read(inode) >> blkbits;
-        while ((probe_block + blocks_per_page) <= last_block &&
-                        page_no < sis->max) {
-                unsigned block_in_page;
-                sector_t first_block;
-
-                first_block = bmap(inode, probe_block);
-                if (first_block == 0)
-                        goto bad_bmap;
-
-                /*
-                 * It must be PAGE_SIZE aligned on-disk
-                 */
-                if (first_block & (blocks_per_page - 1)) {
-                        probe_block++;
-                        goto reprobe;
-                }
-
-                for (block_in_page = 1; block_in_page < blocks_per_page;
-                                        block_in_page++) {
-                        sector_t block;
-
-                        block = bmap(inode, probe_block + block_in_page);
-                        if (block == 0)
-                                goto bad_bmap;
-                        if (block != first_block + block_in_page) {
-                                /* Discontiguity */
-                                probe_block++;
-                                goto reprobe;
-                        }
-                }
-
-                first_block >>= (PAGE_SHIFT - blkbits);
-                if (page_no) {  /* exclude the header page */
-                        if (first_block < lowest_block)
-                                lowest_block = first_block;
-                        if (first_block > highest_block)
-                                highest_block = first_block;
-                }
-
-                /*
-                 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
-                 */
-                ret = add_swap_extent(sis, page_no, 1, first_block);
-                if (ret < 0)
-                        goto out;
-                nr_extents += ret;
-                page_no++;
-                probe_block += blocks_per_page;
-reprobe:
-                continue;
-        }
-        ret = nr_extents;
-        *span = 1 + highest_block - lowest_block;
-        if (page_no == 0)
-                page_no = 1;    /* force Empty message */
-        sis->max = page_no;
-        sis->pages = page_no - 1;
-        sis->highest_bit = page_no - 1;
-out:
-        return ret;
-bad_bmap:
-        printk(KERN_ERR "swapon: swapfile has holes\n");
-        ret = -EINVAL;
-        goto out;
+        return generic_swapfile_activate(sis, swap_file, span);
 }
 
 static void enable_swap_info(struct swap_info_struct *p, int prio,