[PATCH v2 0/3] zram: add rw_page implementation for zram and clean up unnecessary parameter

[k***@lge.com]

From: "karam.lee" <***@lge.com>

Recently rw_page block device operation has been added.
This patchset implements rw_page operation for zram block device
and does some clean-up .

I implemented the feature in zram and tested it.
Test bed was the G2, LG electronic mobile device, whtich has msm8974
processor and 2GB memory.
With a memory allocation test program consuming memory, the system
generates swap.
And operating time of swap_write_page() was measured.

--------------------------------------------------
| | operating time | improvement |
| | (20 runs average) | |
--------------------------------------------------
|with patch | 1087.35 us | |
--------------------------------------------------
|without patch| 1061.15 us | +2.4% |
--------------------------------------------------

Each test(with paged_io,with BIO) result set shows normal distribution
and has equal variance.
I mean the two values are valid result to compare.
I can say operation with paged I/O(without BIO) is faster 2.4% with
confidence level 95%.

Patches 1~2 are for clean-up.
Patch 3 is for implementation of rw_page operation.
With the rw_page operation, zram can do I/O without allocating a BIO.
It make zram can save time and memory.

karam.lee (3):
zram: remove bio parameter from zram_bvec_rw().
zram: change parameter from vaild_io_request()
zram: implement rw_page operation of zram

drivers/block/zram/zram_drv.c | 69 +++++++++++++++++++++++++++++++----------
1 file changed, 53 insertions(+), 16 deletions(-)

[k***@lge.com]

From: "karam.lee" <***@lge.com>

This patch implements rw_page operation for zram block device.

Signed-off-by: karam.lee <***@lge.com>
---
drivers/block/zram/zram_drv.c | 37 +++++++++++++++++++++++++++++++++++++
1 file changed, 37 insertions(+)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index b0c3a20..a44aab0 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -810,8 +810,45 @@ static void zram_slot_free_notify(struct block_device *bdev,
atomic64_inc(&zram->stats.notify_free);
}

+static int zram_rw_page(struct block_device *bdev, sector_t sector,
+ struct page *page, int rw)
+{
+ int offset, ret = 1;
+ u32 index;
+ struct zram *zram;
+ struct bio_vec bv;
+
+ zram = bdev->bd_disk->private_data;
+ if (!valid_io_request(zram, sector, PAGE_SIZE)) {
+ atomic64_inc(&zram->stats.invalid_io);
+ goto out;
+ }
+
+ down_read(&zram->init_lock);
+ if (unlikely(!init_done(zram))) {
+ ret = -ENOMEM;
+ goto out_unlock;
+ }
+
+ index = sector >> SECTORS_PER_PAGE_SHIFT;
+ offset = sector & (SECTORS_PER_PAGE - 1) << SECTOR_SHIFT;
+
+ bv.bv_page = page;
+ bv.bv_len = PAGE_SIZE;
+ bv.bv_offset = 0;
+
+ ret = zram_bvec_rw(zram, &bv, index, offset, rw);
+ page_endio(page, rw, ret);
+
+out_unlock:
+ up_read(&zram->init_lock);
+out:
+ return ret;
+}
+
static const struct block_device_operations zram_devops = {
.swap_slot_free_notify = zram_slot_free_notify,
+ .rw_page = zram_rw_page,
.owner = THIS_MODULE
};

[Minchan Kim]

Post by k***@lge.com
This patch implements rw_page operation for zram block device.

The description is not good. I know you added lots of words in
cover-letter but this patch is key so it should include more words
as well as cover-letter.

Post by k***@lge.com
---
drivers/block/zram/zram_drv.c | 37 +++++++++++++++++++++++++++++++++++++
1 file changed, 37 insertions(+)
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index b0c3a20..a44aab0 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -810,8 +810,45 @@ static void zram_slot_free_notify(struct block_device *bdev,
atomic64_inc(&zram->stats.notify_free);
}
+static int zram_rw_page(struct block_device *bdev, sector_t sector,
+ struct page *page, int rw)
+{
+ int offset, ret = 1;
+ u32 index;
+ struct zram *zram;
+ struct bio_vec bv;
+
+ zram = bdev->bd_disk->private_data;
+ if (!valid_io_request(zram, sector, PAGE_SIZE)) {
+ atomic64_inc(&zram->stats.invalid_io);

-EINVAL?

Otherwise, looks good to me.

Post by k***@lge.com
+ goto out;
+ }
+
+ down_read(&zram->init_lock);
+ if (unlikely(!init_done(zram))) {
+ ret = -ENOMEM;
+ goto out_unlock;
+ }
+
+ index = sector >> SECTORS_PER_PAGE_SHIFT;
+ offset = sector & (SECTORS_PER_PAGE - 1) << SECTOR_SHIFT;
+
+ bv.bv_page = page;
+ bv.bv_len = PAGE_SIZE;
+ bv.bv_offset = 0;
+
+ ret = zram_bvec_rw(zram, &bv, index, offset, rw);
+ page_endio(page, rw, ret);
+
+ up_read(&zram->init_lock);
+ return ret;
+}
+
static const struct block_device_operations zram_devops = {
.swap_slot_free_notify = zram_slot_free_notify,
+ .rw_page = zram_rw_page,
.owner = THIS_MODULE
};
--
1.7.9.5
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[k***@lge.com]

From: "karam.lee" <***@lge.com>

This patch removes an unnecessary parameter(bio)
from zram_bvec_rw() and zram_bvec_read().
zram_bvec_read() doesn't use a bio parameter, so remove it.
zram_bvec_rw() calls a read/write operation not using bio, so a rw parameter
replaces a bio parameter.

Signed-off-by: karam.lee <***@lge.com>
---
drivers/block/zram/zram_drv.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 48eccb3..54da18a 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -368,7 +368,7 @@ static int zram_decompress_page(struct zram *zram, char *mem, u32 index)
}

static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
- u32 index, int offset, struct bio *bio)
+ u32 index, int offset)
{
int ret;
struct page *page;
@@ -535,14 +535,13 @@ out:
}

static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index,
- int offset, struct bio *bio)
+ int offset, int rw)
{
int ret;
- int rw = bio_data_dir(bio);

if (rw == READ) {
atomic64_inc(&zram->stats.num_reads);
- ret = zram_bvec_read(zram, bvec, index, offset, bio);
+ ret = zram_bvec_read(zram, bvec, index, offset);
} else {
atomic64_inc(&zram->stats.num_writes);
ret = zram_bvec_write(zram, bvec, index, offset);
@@ -718,7 +717,7 @@ out:

static void __zram_make_request(struct zram *zram, struct bio *bio)
{
- int offset;
+ int offset, rw;
u32 index;
struct bio_vec bvec;
struct bvec_iter iter;
@@ -733,6 +732,7 @@ static void __zram_make_request(struct zram *zram, struct bio *bio)
return;
}

+ rw = bio_data_dir(bio);
bio_for_each_segment(bvec, bio, iter) {
int max_transfer_size = PAGE_SIZE - offset;

@@ -747,15 +747,15 @@ static void __zram_make_request(struct zram *zram, struct bio *bio)
bv.bv_len = max_transfer_size;
bv.bv_offset = bvec.bv_offset;

- if (zram_bvec_rw(zram, &bv, index, offset, bio) < 0)
+ if (zram_bvec_rw(zram, &bv, index, offset, rw) < 0)
goto out;

bv.bv_len = bvec.bv_len - max_transfer_size;
bv.bv_offset += max_transfer_size;
- if (zram_bvec_rw(zram, &bv, index + 1, 0, bio) < 0)
+ if (zram_bvec_rw(zram, &bv, index + 1, 0, rw) < 0)
goto out;
} else
- if (zram_bvec_rw(zram, &bvec, index, offset, bio) < 0)
+ if (zram_bvec_rw(zram, &bvec, index, offset, rw) < 0)
goto out;

update_position(&index, &offset, &bvec);

[Minchan Kim]

Post by k***@lge.com
This patch removes an unnecessary parameter(bio)
from zram_bvec_rw() and zram_bvec_read().
zram_bvec_read() doesn't use a bio parameter, so remove it.
zram_bvec_rw() calls a read/write operation not using bio, so a rw parameter
replaces a bio parameter.

Acked-by: Minchan Kim <***@kernel.org>

-
Kind regards,
Minchan Kim

[k***@lge.com]

From: "karam.lee" <***@lge.com>

This patch changes parameter of valid_io_request for common usage.
The purpose of valid_io_request() is to determine if bio request is
valid or not.
This patch use I/O start address and size instead of a BIO parameter
for common usage.

Signed-off-by: karam.lee <***@lge.com>
---
drivers/block/zram/zram_drv.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 54da18a..b0c3a20 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -206,19 +206,18 @@ static inline int is_partial_io(struct bio_vec *bvec)
/*
* Check if request is within bounds and aligned on zram logical blocks.
*/
-static inline int valid_io_request(struct zram *zram, struct bio *bio)
+static inline int valid_io_request(struct zram *zram,
+ sector_t start, unsigned int size)
{
- u64 start, end, bound;
+ u64 end, bound;

/* unaligned request */
- if (unlikely(bio->bi_iter.bi_sector &
- (ZRAM_SECTOR_PER_LOGICAL_BLOCK - 1)))
+ if (unlikely(start & (ZRAM_SECTOR_PER_LOGICAL_BLOCK - 1)))
return 0;
- if (unlikely(bio->bi_iter.bi_size & (ZRAM_LOGICAL_BLOCK_SIZE - 1)))
+ if (unlikely(size & (ZRAM_LOGICAL_BLOCK_SIZE - 1)))
return 0;

- start = bio->bi_iter.bi_sector;
- end = start + (bio->bi_iter.bi_size >> SECTOR_SHIFT);
+ end = start + (size >> SECTOR_SHIFT);
bound = zram->disksize >> SECTOR_SHIFT;
/* out of range range */
if (unlikely(start >= bound || end > bound || start > end))
@@ -780,7 +779,8 @@ static void zram_make_request(struct request_queue *queue, struct bio *bio)
if (unlikely(!init_done(zram)))
goto error;

- if (!valid_io_request(zram, bio)) {
+ if (valid_io_request(zram, bio->bi_iter.bi_sector,
+ bio->bi_iter.bi_size)) {
atomic64_inc(&zram->stats.invalid_io);
goto error;
}

[Minchan Kim]

Post by k***@lge.com
This patch changes parameter of valid_io_request for common usage.
The purpose of valid_io_request() is to determine if bio request is
valid or not.
This patch use I/O start address and size instead of a BIO parameter
for common usage.

Acked-by: Minchan Kim <***@kernel.org>