linux-kernel - Subject: [PATCH V7 1/4] mm: frontswap: swap data structure changes

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Message-ID: <20110823145755.GA23174@ca-server1.us.oracle.com>
Date:	Tue, 23 Aug 2011 07:57:55 -0700
From:	Dan Magenheimer <dan.magenheimer@...cle.com>
To:	linux-kernel@...r.kernel.org, linux-mm@...ck.org, jeremy@...p.org,
	hughd@...gle.com, ngupta@...are.org, konrad.wilk@...cle.com,
	JBeulich@...ell.com, kurt.hackel@...cle.com, npiggin@...nel.dk,
	akpm@...ux-foundation.org, riel@...hat.com, hannes@...xchg.org,
	matthew@....cx, chris.mason@...cle.com, dan.magenheimer@...cle.com,
	sjenning@...ux.vnet.ibm.com, jackdachef@...il.com,
	cyclonusj@...il.com
Subject: Subject: [PATCH V7 1/4] mm: frontswap: swap data structure changes

From: Dan Magenheimer <dan.magenheimer@...cle.com>
Subject: [PATCH V7 1/4] 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.

[v7: rebase to 3.0-rc3]
[v7: JBeulich@...ell.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@...cle.com>
Reviewed-by: Konrad Wilk <konrad.wilk@...cle.com>
Acked-by: Jan Beulich <JBeulich@...ell.com>
Acked-by: Seth Jennings <sjenning@...ux.vnet.ibm.com>
Cc: Jeremy Fitzhardinge <jeremy@...p.org>
Cc: Hugh Dickins <hughd@...gle.com>
Cc: Johannes Weiner <hannes@...xchg.org>
Cc: Nitin Gupta <ngupta@...are.org>
Cc: Matthew Wilcox <matthew@....cx>
Cc: Chris Mason <chris.mason@...cle.com>
Cc: Rik Riel <riel@...hat.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>

--- linux/include/linux/swapfile.h	1969-12-31 17:00:00.000000000 -0700
+++ frontswap/include/linux/swapfile.h	2011-08-23 08:20:09.757818005 -0600
@@ -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 */
--- linux/include/linux/swap.h	2011-08-08 08:19:25.880690134 -0600
+++ frontswap/include/linux/swap.h	2011-08-23 08:27:57.584694638 -0600
@@ -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 */
+	unsigned int frontswap_pages;	/* frontswap pages in-use counter */
+#endif
 };
 
 struct swap_list_t {
--
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