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zram/xvmalloc: 64K page fixes and optimizations

PATCH In review Robert Jennings 3 participants 18 messages Jan 28, 2011 – Jan 31, 2011 Staging

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Robert Jennings

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#0 lore raw

v2 cover zram/xvmalloc: 64K page fixes and optimizations

Based on feedback this is version 2 of my patches to fix zram and the xvmalloc allocator for 64K page size kernels along with a few small zram optimizations.

I have dropped the patch to mark the device as non-rotational media as this was duplicated elsewhere. I also dropped the patch regarding caching the indices for page size allocations because gcc is quite smart.

There are two new patches at the end of this patch set. The first changes zram to return zero'd pages for reads of pages which have not been written to, this eliminates passing uninitialized pages back to user-space. The second new patch cleans up freelist pointer management and combines the two delete node functions into one common function.

The xvmalloc allocator is non-functional when running with a 64K page size. The first two patches fix 64K page related issues. [1/7] [v2] zram/vmalloc: Correct tunings to enable use with 64K pages [2/7] [v2] zram: Prevent overflow in logical block size

The next 3 patches provide some small optimizations for zram and xvmalloc.
[3/7] [v2] zram/xvmalloc: free bit block insertion optimization [4/7] [v2] zram/xvmalloc: create CONFIG_ZRAM_DEBUG for debug code [5/7] [v2] zram/xvmalloc: Close 32byte hole on 64bit CPUs

These last 2 patches are new, see the description above. [6/7] zram: Return zero'd pages on new reads [7/7] zram/xvmalloc: combine duplicate block delete code

Thanks for the helpful reviews.

Regards,
Robert Jennings

author
#1 lore raw

PATCH v2 1/7 zram/vmalloc: Correct tunings to enable use with 64K pages

xvmalloc will not currently function with 64K pages. Newly allocated pages will be inserted at an offset beyond the end of the first-level index. This tuning is needed to properly size the allocator for 64K pages.

The default 3 byte shift results in a second level list size which can not be indexed using the 64 bits of the flbitmap in the xv_pool structure. The shift must increase to 4 bytes between second level list entries to fit the size of the first level bitmap.

Here are a few statistics for structure sizes on 32- and 64-bit CPUs with 4KB and 64KB page sizes.

bits_per_long 32 64 64
page_size 4,096 4,096 65,535

xv_align                    4         8         8
fl_delta                    3         3         4

num_free_lists 508 508 4,094
xv_pool size 4,144b 8,216b 66,040b
per object overhead 32 64 64
zram struct 0.5GB disk 512KB 1024KB 64KB

This patch maintains the current tunings for 4K pages, adds an optimal sizing for 64K pages and adds a safe tuning for any other page sizes.

Signed-off-by Robert Jennings <[email protected]>
---
 drivers/staging/zram/xvmalloc_int.h |   16 ++++++++++++++--
 1 files changed, 14 insertions(+), 2 deletions(-)
drivers/staging/zram/xvmalloc_int.h +14 -2
index e23ed5c..82a31fb 100644
@@ -19,7 +19,11 @@
 /* User configurable params */
 
 /* Must be power of two */
+#ifdef CONFIG_64BIT
+#define XV_ALIGN_SHIFT 3
+#else
 #define XV_ALIGN_SHIFT	2
+#endif
 #define XV_ALIGN	(1 << XV_ALIGN_SHIFT)
 #define XV_ALIGN_MASK	(XV_ALIGN - 1)
 

@@ -27,8 +31,16 @@
 #define XV_MIN_ALLOC_SIZE	32
 #define XV_MAX_ALLOC_SIZE	(PAGE_SIZE - XV_ALIGN)
 
-/* Free lists are separated by FL_DELTA bytes */
-#define FL_DELTA_SHIFT	3
+/*
+ * Free lists are separated by FL_DELTA bytes
+ * This value is 3 for 4k pages and 4 for 64k pages, for any
+ * other page size, a conservative (PAGE_SHIFT - 9) is used.
+ */
+#if PAGE_SHIFT == 16
+#define FL_DELTA_SHIFT 4
+#else
+#define FL_DELTA_SHIFT (PAGE_SHIFT - 9)
+#endif
 #define FL_DELTA	(1 << FL_DELTA_SHIFT)
 #define FL_DELTA_MASK	(FL_DELTA - 1)
 #define NUM_FREE_LISTS	((XV_MAX_ALLOC_SIZE - XV_MIN_ALLOC_SIZE) \
Signature · 1 line
1.7.0.4
Reviewed-by on v2 1/7
#2 lore raw

Re: [PATCH 1/7] [v2] zram/vmalloc: Correct tunings to enable use with 64K pages

Quoted 22 lines · Robert Jennings

xvmalloc will not currently function with 64K pages. Newly allocated pages will be inserted at an offset beyond the end of the first-level index. This tuning is needed to properly size the allocator for 64K pages.

The default 3 byte shift results in a second level list size which can not be indexed using the 64 bits of the flbitmap in the xv_pool structure. The shift must increase to 4 bytes between second level list entries to fit the size of the first level bitmap.

Here are a few statistics for structure sizes on 32- and 64-bit CPUs with 4KB and 64KB page sizes.

bits_per_long 32 64 64
page_size 4,096 4,096 65,535

xv_align                    4         8         8
fl_delta                    3         3         4

num_free_lists 508 508 4,094
xv_pool size 4,144b 8,216b 66,040b
per object overhead 32 64 64
zram struct 0.5GB disk 512KB 1024KB 64KB

Quoted 4 lines

This patch maintains the current tunings for 4K pages, adds an optimal sizing for 64K pages and adds a safe tuning for any other page sizes.

Signed-off-by Robert Jennings <[email protected]>
Reviewed-by Pekka Enberg <[email protected]>
author
#3 lore raw

PATCH v2 2/7 zram: Prevent overflow in logical block size

In reply to Robert Jennings

On a 64K page kernel, the value PAGE_SIZE passed to blk_queue_logical_block_size would overflow the logical block size argument (resulting in setting it to 0).

This patch sets the logical block size to 4096, using a new ZRAM_LOGICAL_BLOCK_SIZE constant.

Signed-off-by Robert Jennings <[email protected]>
---
 drivers/staging/zram/zram_drv.c |    3 ++-
 drivers/staging/zram/zram_drv.h |    1 +
 2 files changed, 3 insertions(+), 1 deletions(-)
drivers/staging/zram/zram_drv.c +2 -1
index 5415712..d85d034 100644
@@ -620,7 +620,8 @@ static int create_device(struct zram *zram, int device_id)
 	 * and n*PAGE_SIZED sized I/O requests.
 	 */
 	blk_queue_physical_block_size(zram->disk->queue, PAGE_SIZE);
-	blk_queue_logical_block_size(zram->disk->queue, PAGE_SIZE);
+	blk_queue_logical_block_size(zram->disk->queue,
+					ZRAM_LOGICAL_BLOCK_SIZE);
 	blk_queue_io_min(zram->disk->queue, PAGE_SIZE);
 	blk_queue_io_opt(zram->disk->queue, PAGE_SIZE);
drivers/staging/zram/zram_drv.h +1 -0
index a481551..408b2c0 100644
@@ -61,6 +61,7 @@ static const unsigned max_zpage_size = PAGE_SIZE / 4 * 3;
 #define SECTOR_SIZE		(1 << SECTOR_SHIFT)
 #define SECTORS_PER_PAGE_SHIFT	(PAGE_SHIFT - SECTOR_SHIFT)
 #define SECTORS_PER_PAGE	(1 << SECTORS_PER_PAGE_SHIFT)
+#define ZRAM_LOGICAL_BLOCK_SIZE	4096
 
 /* Flags for zram pages (table[page_no].flags) */
 enum zram_pageflags {
Signature · 1 line
1.7.0.4
Reviewed-by on v2 2/7
#4 lore raw

Re: [PATCH 2/7] [v2] zram: Prevent overflow in logical block size

Quoted 8 lines · Robert Jennings

On a 64K page kernel, the value PAGE_SIZE passed to blk_queue_logical_block_size would overflow the logical block size argument (resulting in setting it to 0).

This patch sets the logical block size to 4096, using a new ZRAM_LOGICAL_BLOCK_SIZE constant.

Signed-off-by Robert Jennings <[email protected]>
Reviewed-by Pekka Enberg <[email protected]>
author
#5 lore raw

PATCH v2 3/7 zram/xvmalloc: free bit block insertion optimization

In reply to Robert Jennings

This change is in a conditional block which is entered only when there is an existing data block on the freelist where the insert has taken place.

The new block is pushed onto the freelist stack and this conditional block is updating links in the prior stack head to point to the new stack head. After this conditional block the first-/second-level indices are updated to indicate that there is a free block at this location.

This patch adds an immediate return from the conditional block to avoid setting bits again to indicate a free block on this freelist. The bits would already be set because there was an existing free block on this freelist.

Signed-off-by Robert Jennings <[email protected]>
---
 drivers/staging/zram/xvmalloc.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
drivers/staging/zram/xvmalloc.c +2 -0
index b644067..149138a 100644
@@ -200,6 +200,8 @@ static void insert_block(struct xv_pool *pool, struct page *page, u32 offset,
 		nextblock->link.prev_page = page;
 		nextblock->link.prev_offset = offset;
 		put_ptr_atomic(nextblock, KM_USER1);
+		/* If there was a next page then the free bits are set. */
+		return;
 	}
 
 	__set_bit(slindex % BITS_PER_LONG, &pool->slbitmap[flindex]);
Signature · 1 line
1.7.0.4
Reviewed-by on v2 3/7
#6 lore raw

Re: [PATCH 3/7] [v2] zram/xvmalloc: free bit block insertion optimization

Quoted 8 lines · Robert Jennings

This change is in a conditional block which is entered only when there is an existing data block on the freelist where the insert has taken place.

The new block is pushed onto the freelist stack and this conditional block is updating links in the prior stack head to point to the new stack head. After this conditional block the first-/second-level indices are updated to indicate that there is a free block at this location.

Quoted 6 lines

This patch adds an immediate return from the conditional block to avoid setting bits again to indicate a free block on this freelist. The bits would already be set because there was an existing free block on this freelist.

Signed-off-by Robert Jennings <[email protected]>
Reviewed-by Pekka Enberg <[email protected]>
author
#7 lore raw

PATCH v2 4/7 zram/xvmalloc: create CONFIG_ZRAM_DEBUG for debug code

In reply to Robert Jennings

Add a debug config flag to enable debug printk output and future debug code.

Signed-off-by Robert Jennings <[email protected]>
---
 drivers/staging/zram/Kconfig    |    8 ++++++++
 drivers/staging/zram/xvmalloc.c |    4 ++++
 drivers/staging/zram/zram_drv.c |    4 ++++
 3 files changed, 16 insertions(+), 0 deletions(-)
drivers/staging/zram/Kconfig +8 -0
index da079f8..d957747 100644
@@ -15,3 +15,11 @@ config ZRAM
 
 	  See zram.txt for more information.
 	  Project home: http://compcache.googlecode.com/
+
+config ZRAM_DEBUG
+	bool "Compressed RAM block device debug support"
+	depends on ZRAM
+	default n
+	help
+	  This option adds additional debugging code to the compressed
+	  RAM block device driver.
drivers/staging/zram/xvmalloc.c +4 -0
index 149138a..0560e9d 100644
@@ -10,6 +10,10 @@
  * Released under the terms of GNU General Public License Version 2.0
  */
 
+#ifdef CONFIG_ZRAM_DEBUG
+#define DEBUG
+#endif
+
 #include <linux/bitops.h>
 #include <linux/errno.h>
 #include <linux/highmem.h>
drivers/staging/zram/zram_drv.c +4 -0
index d85d034..c67060c 100644
@@ -15,6 +15,10 @@
 #define KMSG_COMPONENT "zram"
 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
 
+#ifdef CONFIG_ZRAM_DEBUG
+#define DEBUG
+#endif
+
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/bio.h>
Signature · 1 line
1.7.0.4
author
#9 lore raw

PATCH v2 5/7 zram/xvmalloc: Close 32byte hole on 64bit CPUs

In reply to Robert Jennings

By swapping the total_pages statistic with the lock we close a hole in the structure for 64-bit CPUs.

Signed-off-by Robert Jennings <[email protected]>
---
 drivers/staging/zram/xvmalloc_int.h |    7 ++-----
 1 files changed, 2 insertions(+), 5 deletions(-)
drivers/staging/zram/xvmalloc_int.h +2 -5
index 82a31fb..b5f1f7f 100644
@@ -87,12 +87,9 @@ struct block_header {
 struct xv_pool {
 	ulong flbitmap;
 	ulong slbitmap[MAX_FLI];
-	spinlock_t lock;
-
+	u64 total_pages;	/* stats */
 	struct freelist_entry freelist[NUM_FREE_LISTS];
-
-	/* stats */
-	u64 total_pages;
+	spinlock_t lock;
 };
 
 #endif
Signature · 1 line
1.7.0.4
author
#11 lore raw

PATCH v2 6/7 zram: Return zero'd pages on new reads

In reply to Robert Jennings

Currently zram will do nothing to the page in the bvec when that page has not been previously written. This allows random data to leak to user space. That can be seen by doing the following:

## Load the module and create a 256Mb zram device called /dev/zram0

 # modprobe zram
 # echo $((256*1024*1024)) > /sys/class/block/zram0/disksize

## Initialize the device by writing zero to the first block

 # dd if=/dev/zero of=/dev/zram0 bs=512 count=1

## Read ~256Mb of memory into a file and hope for something interesting

 # dd if=/dev/zram0 of=file

This patch will treat an unwritten page as a zero-filled page. If a page is read before a write has occurred the data returned is all 0's.

Signed-off-by Robert Jennings <[email protected]>
---
 drivers/staging/zram/zram_drv.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
drivers/staging/zram/zram_drv.c +1 -1
index c67060c..86066fd 100644
@@ -238,7 +238,7 @@ static int zram_read(struct zram *zram, struct bio *bio)
 		if (unlikely(!zram->table[index].page)) {
 			pr_debug("Read before write: sector=%lu, size=%u",
 				(ulong)(bio->bi_sector), bio->bi_size);
-			/* Do nothing */
+			handle_zero_page(page);
 			continue;
 		}
Signature · 1 line
1.7.0.4
Reviewed-by on v2 6/7
#12 lore raw

Re: [PATCH 6/7] zram: Return zero'd pages on new reads

Quoted 11 lines · Robert Jennings

Currently zram will do nothing to the page in the bvec when that page has not been previously written. This allows random data to leak to user space. That can be seen by doing the following:

## Load the module and create a 256Mb zram device called /dev/zram0

 # modprobe zram
 # echo $((256*1024*1024)) > /sys/class/block/zram0/disksize

## Initialize the device by writing zero to the first block

 # dd if=/dev/zero of=/dev/zram0 bs=512 count=1
Quoted 7 lines

## Read ~256Mb of memory into a file and hope for something interesting

 # dd if=/dev/zram0 of=file

This patch will treat an unwritten page as a zero-filled page. If a page is read before a write has occurred the data returned is all 0's.

Signed-off-by Robert Jennings <[email protected]>
Reviewed-by Pekka Enberg <[email protected]>
author
#13 lore raw

PATCH v2 7/7 zram/xvmalloc: combine duplicate block delete code

In reply to Robert Jennings

This patch eliminates duplicate code. The remove_block_head function is a special case of remove_block which can be contained in remove_block without confusion.

The portion of code in remove_block_head which was noted as "DEBUG ONLY" is now mandatory. Doing this provides consistent management of the double linked list of blocks under a freelist and makes this consolidation of delete block code safe. The first and last blocks will have NULL pointers in their previous and next page pointers respectively.

Additionally, any time a block is removed from a free list the next and previous pointers will be set to NULL to avoid misuse outside xvmalloc.

Signed-off-by Robert Jennings <[email protected]>
---
 drivers/staging/zram/xvmalloc.c |   73 ++++++++++++++++----------------------
 1 files changed, 31 insertions(+), 42 deletions(-)
drivers/staging/zram/xvmalloc.c +31 -42
index 0560e9d..fc4a3df 100644
@@ -213,54 +213,14 @@ static void insert_block(struct xv_pool *pool, struct page *page, u32 offset,
 }
 
 /*
- * Remove block from head of freelist. Index 'slindex' identifies the freelist.
- */
-static void remove_block_head(struct xv_pool *pool,
-			struct block_header *block, u32 slindex)
-{
-	struct block_header *tmpblock;
-	u32 flindex = slindex / BITS_PER_LONG;
-
-	pool->freelist[slindex].page = block->link.next_page;
-	pool->freelist[slindex].offset = block->link.next_offset;
-	block->link.prev_page = NULL;
-	block->link.prev_offset = 0;
-
-	if (!pool->freelist[slindex].page) {
-		__clear_bit(slindex % BITS_PER_LONG, &pool->slbitmap[flindex]);
-		if (!pool->slbitmap[flindex])
-			__clear_bit(flindex, &pool->flbitmap);
-	} else {
-		/*
-		 * DEBUG ONLY: We need not reinitialize freelist head previous
-		 * pointer to 0 - we never depend on its value. But just for
-		 * sanity, lets do it.
-		 */
-		tmpblock = get_ptr_atomic(pool->freelist[slindex].page,
-				pool->freelist[slindex].offset, KM_USER1);
-		tmpblock->link.prev_page = NULL;
-		tmpblock->link.prev_offset = 0;
-		put_ptr_atomic(tmpblock, KM_USER1);
-	}
-}
-
-/*
  * Remove block from freelist. Index 'slindex' identifies the freelist.
  */
 static void remove_block(struct xv_pool *pool, struct page *page, u32 offset,
 			struct block_header *block, u32 slindex)
 {
-	u32 flindex;
+	u32 flindex = slindex / BITS_PER_LONG;
 	struct block_header *tmpblock;
 
-	if (pool->freelist[slindex].page == page
-	   && pool->freelist[slindex].offset == offset) {
-		remove_block_head(pool, block, slindex);
-		return;
-	}
-
-	flindex = slindex / BITS_PER_LONG;
-
 	if (block->link.prev_page) {
 		tmpblock = get_ptr_atomic(block->link.prev_page,
 				block->link.prev_offset, KM_USER1);

@@ -276,6 +236,35 @@ static void remove_block(struct xv_pool *pool, struct page *page, u32 offset,
 		tmpblock->link.prev_offset = block->link.prev_offset;
 		put_ptr_atomic(tmpblock, KM_USER1);
 	}
+
+	/* Is this block is at the head of the freelist? */
+	if (pool->freelist[slindex].page == page
+	   && pool->freelist[slindex].offset == offset) {
+
+		pool->freelist[slindex].page = block->link.next_page;
+		pool->freelist[slindex].offset = block->link.next_offset;
+
+		if (pool->freelist[slindex].page) {
+			struct block_header *tmpblock;
+			tmpblock = get_ptr_atomic(pool->freelist[slindex].page,
+					pool->freelist[slindex].offset,
+					KM_USER1);
+			tmpblock->link.prev_page = NULL;
+			tmpblock->link.prev_offset = 0;
+			put_ptr_atomic(tmpblock, KM_USER1);
+		} else {
+			/* This freelist bucket is empty */
+			__clear_bit(slindex % BITS_PER_LONG,
+				    &pool->slbitmap[flindex]);
+			if (!pool->slbitmap[flindex])
+				__clear_bit(flindex, &pool->flbitmap);
+		}
+	}
+
+	block->link.prev_page = NULL;
+	block->link.prev_offset = 0;
+	block->link.next_page = NULL;
+	block->link.next_offset = 0;
 }
 
 /*

@@ -384,7 +373,7 @@ int xv_malloc(struct xv_pool *pool, u32 size, struct page **page,
 
 	block = get_ptr_atomic(*page, *offset, KM_USER0);
 
-	remove_block_head(pool, block, index);
+	remove_block(pool, *page, *offset, block, index);
 
 	/* Split the block if required */
 	tmpoffset = *offset + size + XV_ALIGN;
Signature · 1 line
1.7.0.4
Reviewed-by on v2 7/7
#14 lore raw

Re: [PATCH 7/7] zram/xvmalloc: combine duplicate block delete code

Quoted 10 lines · Robert Jennings

This patch eliminates duplicate code. The remove_block_head function is a special case of remove_block which can be contained in remove_block without confusion.

The portion of code in remove_block_head which was noted as "DEBUG ONLY" is now mandatory. Doing this provides consistent management of the double linked list of blocks under a freelist and makes this consolidation of delete block code safe. The first and last blocks will have NULL pointers in their previous and next page pointers respectively.

Quoted 4 lines

Additionally, any time a block is removed from a free list the next and previous pointers will be set to NULL to avoid misuse outside xvmalloc.

Signed-off-by Robert Jennings <[email protected]>

Looks OK to me but we should really get Nitin's ACK for this.

Reviewed-by Pekka Enberg <[email protected]>
Acked-by on v2 7/7
#15 lore raw

Re: [PATCH 7/7] zram/xvmalloc: combine duplicate block delete code

In reply to Robert Jennings
Quoted 10 lines · Robert Jennings

This patch eliminates duplicate code. The remove_block_head function is a special case of remove_block which can be contained in remove_block without confusion.

The portion of code in remove_block_head which was noted as "DEBUG ONLY" is now mandatory. Doing this provides consistent management of the double linked list of blocks under a freelist and makes this consolidation of delete block code safe. The first and last blocks will have NULL pointers in their previous and next page pointers respectively.

Quoted 4 lines

Additionally, any time a block is removed from a free list the next and previous pointers will be set to NULL to avoid misuse outside xvmalloc.

Signed-off-by Robert Jennings<[email protected]>

The reason for introducing remove_block_head() as a separate function was to make malloc slightly faster but since I lack any profiling data, I'm not very sure if this may impact performance. Ideally, some sort of data with some malloc heavy test would have been useful. Anyways, I think major allocator changes will happen when we make xvmalloc allocated memory reclaimable, so maybe we can defer profiling.

Acked-by Nitin Gupta <[email protected]>

Thanks,
Nitin

#16 lore raw
In reply to Robert Jennings
Quoted 26 lines · Robert Jennings

Based on feedback this is version 2 of my patches to fix zram and the xvmalloc allocator for 64K page size kernels along with a few small zram optimizations.

I have dropped the patch to mark the device as non-rotational media as this was duplicated elsewhere. I also dropped the patch regarding caching the indices for page size allocations because gcc is quite smart.

There are two new patches at the end of this patch set. The first changes zram to return zero'd pages for reads of pages which have not been written to, this eliminates passing uninitialized pages back to user-space. The second new patch cleans up freelist pointer management and combines the two delete node functions into one common function.

The xvmalloc allocator is non-functional when running with a 64K page size. The first two patches fix 64K page related issues. [1/7] [v2] zram/vmalloc: Correct tunings to enable use with 64K pages [2/7] [v2] zram: Prevent overflow in logical block size

The next 3 patches provide some small optimizations for zram and xvmalloc.
[3/7] [v2] zram/xvmalloc: free bit block insertion optimization [4/7] [v2] zram/xvmalloc: create CONFIG_ZRAM_DEBUG for debug code [5/7] [v2] zram/xvmalloc: Close 32byte hole on 64bit CPUs

Quoted 5 lines

These last 2 patches are new, see the description above. [6/7] zram: Return zero'd pages on new reads [7/7] zram/xvmalloc: combine duplicate block delete code

Thanks for the helpful reviews.

Hey, you dropped Nitin's and my Reviewed-by tags! Please don't do that in the future.

Pekka

author
#17 lore raw
Quoted 31 lines · * Pekka Enberg ([email protected]) wrote:
Quoted 30 lines · Robert Jennings

Based on feedback this is version 2 of my patches to fix zram and the xvmalloc allocator for 64K page size kernels along with a few small zram optimizations.

I have dropped the patch to mark the device as non-rotational media as this was duplicated elsewhere. I also dropped the patch regarding caching the indices for page size allocations because gcc is quite smart.

There are two new patches at the end of this patch set. The first changes zram to return zero'd pages for reads of pages which have not been written to, this eliminates passing uninitialized pages back to user-space. The second new patch cleans up freelist pointer management and combines the two delete node functions into one common function.

The xvmalloc allocator is non-functional when running with a 64K page size. The first two patches fix 64K page related issues. [1/7] [v2] zram/vmalloc: Correct tunings to enable use with 64K pages [2/7] [v2] zram: Prevent overflow in logical block size

The next 3 patches provide some small optimizations for zram and xvmalloc.
[3/7] [v2] zram/xvmalloc: free bit block insertion optimization [4/7] [v2] zram/xvmalloc: create CONFIG_ZRAM_DEBUG for debug code [5/7] [v2] zram/xvmalloc: Close 32byte hole on 64bit CPUs

These last 2 patches are new, see the description above. [6/7] zram: Return zero'd pages on new reads [7/7] zram/xvmalloc: combine duplicate block delete code

Quoted 7 lines
Quoted 1 line

Thanks for the helpful reviews.

Hey, you dropped Nitin's and my Reviewed-by tags! Please don't do that in the future.

Pekka

Very sorry about that, it was not my intention to drop the Reviewed-by tags on the unchanged patches. Thank you for reviewing these patches.

--Robert Jennings