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zram: support page writeback 

There is demand to writeback specific process pages to backing store
instead of all idles pages in the system due to storage wear out concerns
and to launching latency of apps which are most of the time idle but are
critical for resume latency.

This patch extends the writeback knob to support a specific page
writeback.

Link: https://lkml.kernel.org/r/20201020190506.3758660-1-minchan@kernel.org
Signed-off-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Minchan Kim 2020-12-14 19:14:28 -08:00 committed by Linus Torvalds
parent 95c9ae14a9
commit 0d8359620d
2 changed files with 22 additions and 4 deletions
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5
Documentation/admin-guide/blockdev/zram.rst
View File

@ -334,6 +334,11 @@ Admin can request writeback of those idle pages at right timing via::
With the command, zram writeback idle pages from memory to the storage.
If admin want to write a specific page in zram device to backing device,
they could write a page index into the interface.
echo "page_index=1251" > /sys/block/zramX/writeback
If there are lots of write IO with flash device, potentially, it has
flash wearout problem so that admin needs to design write limitation
to guarantee storage health for entire product life.

21
drivers/block/zram/zram_drv.c
View File

@ -620,15 +620,19 @@ static int read_from_bdev_async(struct zram *zram, struct bio_vec *bvec,
return 1;
}
#define PAGE_WB_SIG "page_index="
#define PAGE_WRITEBACK 0
#define HUGE_WRITEBACK 1
#define IDLE_WRITEBACK 2
static ssize_t writeback_store(struct device *dev,
struct device_attribute *attr, const char *buf, size_t len)
{
struct zram *zram = dev_to_zram(dev);
unsigned long nr_pages = zram->disksize >> PAGE_SHIFT;
unsigned long index;
unsigned long index = 0;
struct bio bio;
struct bio_vec bio_vec;
struct page *page;
@ -640,8 +644,17 @@ static ssize_t writeback_store(struct device *dev,
mode = IDLE_WRITEBACK;
else if (sysfs_streq(buf, "huge"))
mode = HUGE_WRITEBACK;
else
return -EINVAL;
else {
if (strncmp(buf, PAGE_WB_SIG, sizeof(PAGE_WB_SIG) - 1))
return -EINVAL;
ret = kstrtol(buf + sizeof(PAGE_WB_SIG) - 1, 10, &index);
if (ret || index >= nr_pages)
return -EINVAL;
nr_pages = 1;
mode = PAGE_WRITEBACK;
}
down_read(&zram->init_lock);
if (!init_done(zram)) {
@ -660,7 +673,7 @@ static ssize_t writeback_store(struct device *dev,
goto release_init_lock;
}
for (index = 0; index < nr_pages; index++) {
while (nr_pages--) {
struct bio_vec bvec;
bvec.bv_page = page;