PM / Hibernate: Hibernate/thaw fixes/improvements

 1. Do not allocate memory for buffers from emergency pools, unless
    absolutely required. Do not warn about and do not retry non-essential
    failed allocations.

 2. Do not check the amount of free pages left on every single page
    write, but wait until one map is completely populated and then check.

 3. Set maximum number of pages for read buffering consistently, instead
    of inadvertently depending on the size of the sector type.

 4. Fix copyright line, which I missed when I submitted the hibernation
    threading patch.

 5. Dispense with bit shifting arithmetic to improve readability.

 6. Really recalculate the number of pages required to be free after all
    allocations have been done.

 7. Fix calculation of pages required for read buffering. Only count in
    pages that do not belong to high memory.
Signed-off-by: Bojan Smojver <bojan@rexursive.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

kernel/power/swap.c

@@ -6,7 +6,7 @@
  *
  * Copyright (C) 1998,2001-2005 Pavel Machek <pavel@ucw.cz>
  * Copyright (C) 2006 Rafael J. Wysocki <rjw@sisk.pl>
- * Copyright (C) 2010 Bojan Smojver <bojan@rexursive.com>
+ * Copyright (C) 2010-2012 Bojan Smojver <bojan@rexursive.com>
  *
  * This file is released under the GPLv2.
  *
@@ -282,14 +282,17 @@ static int write_page(void *buf, sector_t offset, struct bio **bio_chain)
 		return -ENOSPC;
 
 	if (bio_chain) {
-		src = (void *)__get_free_page(__GFP_WAIT | __GFP_HIGH);
+		src = (void *)__get_free_page(__GFP_WAIT | __GFP_NOWARN |
+		                              __GFP_NORETRY);
 		if (src) {
 			copy_page(src, buf);
 		} else {
 			ret = hib_wait_on_bio_chain(bio_chain); /* Free pages */
 			if (ret)
 				return ret;
-			src = (void *)__get_free_page(__GFP_WAIT | __GFP_HIGH);
+			src = (void *)__get_free_page(__GFP_WAIT |
+			                              __GFP_NOWARN |
+			                              __GFP_NORETRY);
 			if (src) {
 				copy_page(src, buf);
 			} else {
@@ -367,13 +370,18 @@ static int swap_write_page(struct swap_map_handle *handle, void *buf,
 		clear_page(handle->cur);
 		handle->cur_swap = offset;
 		handle->k = 0;
-	}
+
 		if (bio_chain && low_free_pages() <= handle->reqd_free_pages) {
 			error = hib_wait_on_bio_chain(bio_chain);
 			if (error)
 				goto out;
+			/*
+			 * Recalculate the number of required free pages, to
+			 * make sure we never take more than half.
+			 */
 			handle->reqd_free_pages = reqd_free_pages();
 		}
+	}
  out:
 	return error;
 }
@@ -419,8 +427,9 @@ static int swap_writer_finish(struct swap_map_handle *handle,
 /* Maximum number of threads for compression/decompression. */
 #define LZO_THREADS	3
 
-/* Maximum number of pages for read buffering. */
-#define LZO_READ_PAGES	(MAP_PAGE_ENTRIES * 8)
+/* Minimum/maximum number of pages for read buffering. */
+#define LZO_MIN_RD_PAGES	1024
+#define LZO_MAX_RD_PAGES	8192
 
 
 /**
@@ -630,12 +639,6 @@ static int save_image_lzo(struct swap_map_handle *handle,
 		}
 	}
 
-	/*
-	 * Adjust number of free pages after all allocations have been done.
-	 * We don't want to run out of pages when writing.
-	 */
-	handle->reqd_free_pages = reqd_free_pages();
-
 	/*
 	 * Start the CRC32 thread.
 	 */
@@ -657,6 +660,12 @@ static int save_image_lzo(struct swap_map_handle *handle,
 		goto out_clean;
 	}
 
+	/*
+	 * Adjust the number of required free pages after all allocations have
+	 * been done. We don't want to run out of pages when writing.
+	 */
+	handle->reqd_free_pages = reqd_free_pages();
+
 	printk(KERN_INFO
 		"PM: Using %u thread(s) for compression.\n"
 		"PM: Compressing and saving image data (%u pages) ...     ",
@@ -1067,7 +1076,7 @@ static int load_image_lzo(struct swap_map_handle *handle,
 	unsigned i, thr, run_threads, nr_threads;
 	unsigned ring = 0, pg = 0, ring_size = 0,
 	         have = 0, want, need, asked = 0;
-	unsigned long read_pages;
+	unsigned long read_pages = 0;
 	unsigned char **page = NULL;
 	struct dec_data *data = NULL;
 	struct crc_data *crc = NULL;
@@ -1079,7 +1088,7 @@ static int load_image_lzo(struct swap_map_handle *handle,
 	nr_threads = num_online_cpus() - 1;
 	nr_threads = clamp_val(nr_threads, 1, LZO_THREADS);
 
-	page = vmalloc(sizeof(*page) * LZO_READ_PAGES);
+	page = vmalloc(sizeof(*page) * LZO_MAX_RD_PAGES);
 	if (!page) {
 		printk(KERN_ERR "PM: Failed to allocate LZO page\n");
 		ret = -ENOMEM;
@@ -1144,15 +1153,22 @@ static int load_image_lzo(struct swap_map_handle *handle,
 	}
 
 	/*
-	 * Adjust number of pages for read buffering, in case we are short.
+	 * Set the number of pages for read buffering.
+	 * This is complete guesswork, because we'll only know the real
+	 * picture once prepare_image() is called, which is much later on
+	 * during the image load phase. We'll assume the worst case and
+	 * say that none of the image pages are from high memory.
 	 */
-	read_pages = (nr_free_pages() - snapshot_get_image_size()) >> 1;
-	read_pages = clamp_val(read_pages, LZO_CMP_PAGES, LZO_READ_PAGES);
+	if (low_free_pages() > snapshot_get_image_size())
+		read_pages = (low_free_pages() - snapshot_get_image_size()) / 2;
+	read_pages = clamp_val(read_pages, LZO_MIN_RD_PAGES, LZO_MAX_RD_PAGES);
 
 	for (i = 0; i < read_pages; i++) {
 		page[i] = (void *)__get_free_page(i < LZO_CMP_PAGES ?
 		                                  __GFP_WAIT | __GFP_HIGH :
-		                                  __GFP_WAIT);
+		                                  __GFP_WAIT | __GFP_NOWARN |
+		                                  __GFP_NORETRY);
+
 		if (!page[i]) {
 			if (i < LZO_CMP_PAGES) {
 				ring_size = i;