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>

diff --git a/include/linux/fs.h b/include/linux/fs.h
index bed4565e525aaad9238a49e3c56150937d580a35..b3db6628cfec07b0e19f0d560e42f33b955fb5ce 100644 (file)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -427,6 +427,7 @@ 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);
@@ -638,8 +639,9 @@ 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 ab230b1ebf6151a7432a8cca3f6b72e3d66a74d1..388e70601413332f6b89c97cccf8b99c0b8381ab 100644 (file)
--- 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 307a3e795290159caab708a39a3915c934cb2cf7..4a379629e31f17f1bc3b93c02b12fb489653cbce 100644 (file)
--- 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 6ffc87602f4a0a00893b61ed056e67fd445f98e3..7307fc928d7b2d2e07bc4ee91ca8e4f7875b9bd0 100644 (file)
--- 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,