mm: swap: implement generic handler for swap_activate

The version of swap_activate introduced is sufficient for swap-over-NFS
but would not provide enough information to implement a generic handler.
This patch shuffles things slightly to ensure the same information is
available for aops->swap_activate() as is available to the core.

No functionality change.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Eric B Munson <emunson@mgebm.net>
Cc: Eric Paris <eparis@redhat.com>
Cc: James Morris <jmorris@namei.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Christie <michaelc@cs.wisc.edu>
Cc: Neil Brown <neilb@suse.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: Xiaotian Feng <dfeng@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 86 deletions

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,