linux-kernel - [PATCH 4/5] Hibernation: Switch to preallocating swap.

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Date:	Wed, 26 May 2010 17:10:07 +1000
From:	Nigel Cunningham <ncunningham@...a.org.au>
To:	"Rafael J. Wysocki" <rjw@...k.pl>,
	pm list <linux-pm@...ts.linux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	TuxOnIce-devel <tuxonice-devel@...ts.tuxonice.net>
Subject: [PATCH 4/5] Hibernation: Switch to preallocating swap.

Switch from allocating swap as the image is written to allocating
storage prior to writing the image.

Signed-off-by: Nigel Cunningham <nigel@...onice.net>
---
  kernel/power/swap.c |   62 
++++++++++++++++++++++++++++++--------------------
  1 files changed, 37 insertions(+), 25 deletions(-)

diff --git a/kernel/power/swap.c b/kernel/power/swap.c
index 550c1ed..ff2fc15 100644
--- a/kernel/power/swap.c
+++ b/kernel/power/swap.c
@@ -201,6 +201,33 @@ int alloc_swapdev_blocks(int needed)
  }

  /**
+ *	allocate_swap - Allocate enough swap to save the image.
+ *
+ *	Calculates the number of swap pages actually needed and seeks
+ *	to allocate that many from the resume partition. Returns TRUE
+ *	or FALSE to indicate whether we got enough storage.
+ */
+
+static int allocate_swap(unsigned int nr_pages)
+{
+	unsigned int free_swap = count_swap_pages(root_swap, 1);
+
+	nr_pages += DIV_ROUND_UP(nr_pages, MAP_PAGE_ENTRIES);
+
+	pr_debug("PM: Free swap pages: %u\n", free_swap);
+	if (free_swap < nr_pages)
+		return 0;
+
+	if (alloc_swapdev_blocks(nr_pages) < nr_pages) {
+		free_all_swap_pages(root_swap);
+		return 0;
+	}
+
+	reset_storage_pos();
+	return 1;
+}
+
+/**
   *	free_all_swap_pages - free swap pages allocated for saving image data.
   *	It also frees the extents used to register which swap entres had been
   *	allocated.
@@ -321,7 +348,7 @@ static void release_swap_writer(struct 
swap_map_handle *handle)
  	handle->cur = NULL;
  }

-static int get_swap_writer(struct swap_map_handle *handle)
+static int get_swap_writer(struct swap_map_handle *handle, unsigned 
long pages)
  {
  	int ret;

@@ -337,7 +364,12 @@ static int get_swap_writer(struct swap_map_handle 
*handle)
  		ret = -ENOMEM;
  		goto err_close;
  	}
-	handle->cur_swap = alloc_swapdev_block(root_swap);
+	if (!allocate_swap(pages)) {
+		printk(KERN_ERR "PM: Not enough free swap\n");
+		ret = -ENOSPC;
+		goto err_close;
+	}
+	handle->cur_swap = next_swapdev_block();
  	if (!handle->cur_swap) {
  		ret = -ENOSPC;
  		goto err_rel;
@@ -360,7 +392,7 @@ static int swap_write_page(struct swap_map_handle 
*handle, void *buf,

  	if (!handle->cur)
  		return -EINVAL;
-	offset = alloc_swapdev_block(root_swap);
+	offset = next_swapdev_block();
  	error = write_page(buf, offset, bio_chain);
  	if (error)
  		return error;
@@ -369,7 +401,7 @@ static int swap_write_page(struct swap_map_handle 
*handle, void *buf,
  		error = hib_wait_on_bio_chain(bio_chain);
  		if (error)
  			goto out;
-		offset = alloc_swapdev_block(root_swap);
+		offset = next_swapdev_block();
  		if (!offset)
  			return -ENOSPC;
  		handle->cur->next_swap = offset;
@@ -458,21 +490,6 @@ static int save_image(struct swap_map_handle *handle,
  }

  /**
- *	enough_swap - Make sure we have enough swap to save the image.
- *
- *	Returns TRUE or FALSE after checking the total amount of swap
- *	space avaiable from the resume partition.
- */
-
-static int enough_swap(unsigned int nr_pages)
-{
-	unsigned int free_swap = count_swap_pages(root_swap, 1);
-
-	pr_debug("PM: Free swap pages: %u\n", free_swap);
-	return free_swap > nr_pages + PAGES_FOR_IO;
-}
-
-/**
   *	swsusp_write - Write entire image and metadata.
   *	@flags: flags to pass to the "boot" kernel in the image header
   *
@@ -491,16 +508,11 @@ int swsusp_write(unsigned int flags)
  	int error;

  	pages = snapshot_get_image_size();
-	error = get_swap_writer(&handle);
+	error = get_swap_writer(&handle, pages);
  	if (error) {
  		printk(KERN_ERR "PM: Cannot get swap writer\n");
  		return error;
  	}
-	if (!enough_swap(pages)) {
-		printk(KERN_ERR "PM: Not enough free swap\n");
-		error = -ENOSPC;
-		goto out_finish;
-	}
  	memset(&snapshot, 0, sizeof(struct snapshot_handle));
  	error = snapshot_read_next(&snapshot);
  	if (error < PAGE_SIZE) {
-- 
1.7.0.4

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