mm: frontswap: swap data structure changes

This first patch of four in the frontswap series makes available core
swap data structures (swap_lock, swap_list and swap_info) that are
needed by frontswap.c but we don't need to expose them to the dozens
of files that include swap.h so we create a new swapfile.h just to
extern-ify these.

Also add frontswap-related elements to swap_info_struct.  Frontswap_map
points to vzalloc'ed one-bit-per-swap-page metadata that indicates
whether the swap page is in frontswap or in the device and frontswap_pages
counts how many pages are in frontswap.

[v8: rebase to 3.0-rc4]
[v8: kamezawa.hiroyu@jp.fujitsu.com: frontswap_pages should be atomic_t]
[v8: kamezawa.hiroyu@jp.fujitsu.com: comment to clarify informational counters]
[v7: rebase to 3.0-rc3]
[v7: JBeulich@novell.com: add new swap struct elements only if config'd]
[v6: rebase to 3.0-rc1]
[v5: no change from v4]
[v4: rebase to 2.6.39]
Signed-off-by: Dan Magenheimer <dan.magenheimer@oracle.com>
Reviewed-by: Konrad Wilk <konrad.wilk@oracle.com>
Reviewed-by: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Jan Beulich <JBeulich@novell.com>
Acked-by: Seth Jennings <sjenning@linux.vnet.ibm.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Matthew Wilcox <matthew@wil.cx>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Rik Riel <riel@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/swap.h b/include/linux/swap.h
index 14d62490922e12bccc319a0827ec22a1d5c3a1b3..5d4edbf889d475d60a88efc51d6731f3e706f78f 100644 (file)
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -194,6 +194,10 @@ struct swap_info_struct {
        struct block_device *bdev;      /* swap device or bdev of swap file */
        struct file *swap_file;         /* seldom referenced */
        unsigned int old_block_size;    /* seldom referenced */
+#ifdef CONFIG_FRONTSWAP
+       unsigned long *frontswap_map;   /* frontswap in-use, one bit per page */
+       atomic_t frontswap_pages;       /* frontswap pages in-use counter */
+#endif
 };
 
 struct swap_list_t {

diff --git a/include/linux/swapfile.h b/include/linux/swapfile.h
new file mode 100644 (file)
index 0000000..e282624
--- /dev/null
+++ b/include/linux/swapfile.h
@@ -0,0 +1,13 @@
+#ifndef _LINUX_SWAPFILE_H
+#define _LINUX_SWAPFILE_H
+
+/*
+ * these were static in swapfile.c but frontswap.c needs them and we don't
+ * want to expose them to the dozens of source files that include swap.h
+ */
+extern spinlock_t swap_lock;
+extern struct swap_list_t swap_list;
+extern struct swap_info_struct *swap_info[];
+extern int try_to_unuse(unsigned int, bool, unsigned long);
+
+#endif /* _LINUX_SWAPFILE_H */