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SubjectRe: [PATCH 01/23] Hibernation: Split compression support out.
Hi.

On 28/09/10 06:27, Rafael J. Wysocki wrote:
> On Monday, September 27, 2010, Nigel Cunningham wrote:
>> Separate compression support out into its own file, removing in
>> the process the duplication of the load_image and save_image
>> functions and some #includes from swap.c that are no longer
>> needed.
>>
>> Signed-off-by: Nigel Cunningham<nigel@tuxonice.net>
>
> If you're at it, I'd like to do something slightly different. Explained below.
>
>> ---
>> kernel/power/Makefile | 2 +-
>> kernel/power/compress.c | 210 +++++++++++++++++++++++++++++
>> kernel/power/compress.h | 23 +++
>> kernel/power/swap.c | 339 +++++------------------------------------------
>> kernel/power/swap.h | 28 ++++
>> 5 files changed, 296 insertions(+), 306 deletions(-)
>> create mode 100644 kernel/power/compress.c
>> create mode 100644 kernel/power/compress.h
>> create mode 100644 kernel/power/swap.h
>>
>> diff --git a/kernel/power/Makefile b/kernel/power/Makefile
>> index f9063c6..2eb134d 100644
>> --- a/kernel/power/Makefile
>> +++ b/kernel/power/Makefile
>> @@ -9,7 +9,7 @@ obj-$(CONFIG_FREEZER) += process.o
>> obj-$(CONFIG_SUSPEND) += suspend.o
>> obj-$(CONFIG_PM_TEST_SUSPEND) += suspend_test.o
>> obj-$(CONFIG_HIBERNATION) += hibernate.o snapshot.o swap.o user.o \
>> - block_io.o
>> + block_io.o compress.o
>> obj-$(CONFIG_SUSPEND_NVS) += nvs.o
>>
>> obj-$(CONFIG_MAGIC_SYSRQ) += poweroff.o
>> diff --git a/kernel/power/compress.c b/kernel/power/compress.c
>> new file mode 100644
>> index 0000000..45725ea
>> --- /dev/null
>> +++ b/kernel/power/compress.c
>> @@ -0,0 +1,210 @@
>> +/*
>> + * linux/kernel/power/compress.c
>> + *
>> + * This file provides functions for (optionally) compressing an
>> + * image as it is being written and decompressing it at resume.
>> + *
>> + * Copyright (C) 2003-2010 Nigel Cunningham<nigel@tuxonice.net>
>> + *
>> + * This file is released under the GPLv2.
>> + *
>> + */
>> +
>> +#include<linux/slab.h>
>> +#include<linux/lzo.h>
>> +#include<linux/vmalloc.h>
>> +
>> +#include "power.h"
>> +#include "swap.h"
>> +
>> +/* We need to remember how much compressed data we need to read. */
>> +#define LZO_HEADER sizeof(size_t)
>> +
>> +/* Number of pages/bytes we'll compress at one time. */
>> +#define LZO_UNC_PAGES 32
>> +#define LZO_UNC_SIZE (LZO_UNC_PAGES * PAGE_SIZE)
>> +
>> +/* Number of pages/bytes we need for compressed data (worst case). */
>> +#define LZO_CMP_PAGES DIV_ROUND_UP(lzo1x_worst_compress(LZO_UNC_SIZE) + \
>> + LZO_HEADER, PAGE_SIZE)
>> +#define LZO_CMP_SIZE (LZO_CMP_PAGES * PAGE_SIZE)
>> +
>> +static size_t off, unc_len, cmp_len;
>> +static unsigned char *unc, *cmp, *wrk, *page;
>> +
>> +void compress_image_cleanup(void)
>> +{
>> + if (cmp) {
>> + vfree(cmp);
>> + cmp = NULL;
>> + }
>> +
>> + if (unc) {
>> + vfree(unc);
>> + unc = NULL;
>> + }
>> +
>> + if (wrk) {
>> + vfree(wrk);
>> + wrk = NULL;
>> + }
>> +
>> + if (page) {
>> + free_page((unsigned long)page);
>> + page = NULL;
>> + }
>> +}
>> +
>> +int compress_image_init(void)
>> +{
>> + page = (void *)__get_free_page(__GFP_WAIT | __GFP_HIGH);
>> + if (!page) {
>> + printk(KERN_ERR "PM: Failed to allocate LZO page\n");
>> + return -ENOMEM;
>> + }
>> +
>> + wrk = vmalloc(LZO1X_1_MEM_COMPRESS);
>> + unc = vmalloc(LZO_UNC_SIZE);
>> + cmp = vmalloc(LZO_CMP_SIZE);
>> +
>> + if (!wrk || !unc || !cmp) {
>> + printk(KERN_ERR "PM: Failed to allocate memory for (de)compression.\n");
>> + compress_image_cleanup();
>> + return -ENOMEM;
>> + }
>> +
>> + off = 0;
>> +
>> + return 0;
>> +}
>> +
>> +static int compress_and_write(struct swap_map_handle *handle, struct bio **bio)
>> +{
>> + int ret;
>> +
>> + if (!off)
>> + return 0;
>> +
>> + unc_len = off;
>> + ret = lzo1x_1_compress(unc, unc_len, cmp + LZO_HEADER,&cmp_len, wrk);
>> +
>> + if (ret< 0) {
>> + printk(KERN_ERR "PM: LZO compression failed\n");
>> + return -EIO;
>> + }
>> +
>> + if (unlikely(!cmp_len ||
>> + cmp_len> lzo1x_worst_compress(unc_len))) {
>> + printk(KERN_ERR "PM: Invalid LZO compressed length\n");
>> + return -EIO;
>> + }
>> +
>> + *(size_t *)cmp = cmp_len;
>> +
>> + /*
>> + * Given we are writing one page at a time to disk, we copy
>> + * that much from the buffer, although the last bit will likely
>> + * be smaller than full page. This is OK - we saved the length
>> + * of the compressed data, so any garbage at the end will be
>> + * discarded when we read it.
>> + */
>> + for (off = 0; off< LZO_HEADER + cmp_len; off += PAGE_SIZE) {
>> + memcpy(page, cmp + off, PAGE_SIZE);
>> +
>> + ret = swap_write_page(handle, page, bio);
>> + if (ret)
>> + return ret;
>> + }
>> +
>> + off = 0;
>> + return 0;
>> +}
>> +
>> +int compress_write(struct swap_map_handle *handle, char *buf, struct bio **bio,
>> + int flags)
>> +{
>> + int ret = 0;
>> +
>> + if (flags& SF_NOCOMPRESS_MODE)
>> + return swap_write_page(handle, buf, bio);
>> +
>> + if (off == LZO_UNC_SIZE)
>> + ret = compress_and_write(handle, bio);
>> +
>> + memcpy(unc + off, buf, PAGE_SIZE);
>> + off += PAGE_SIZE;
>> + return ret;
>> +}
>
> This one doesn't really good to me. What I'd prefer would be to have a
> structure of "swap operations" pointers like ->start(), ->write_data(),
> ->read_data(), and ->finish() that will point to the functions in this file
> (if compression is to be used) or to the "old" swap_write_page()/swap_read_page()
> otherwise. That would reduce the number of the
> (flags& SF_NOCOMPRESS_MODE) checks quite substantially and will likely result
> in code that's easier to follow.

Me too. I was heading in that direction, but not doing it in one step.
I'll happily change that.

Nigel


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