The zswap_load() and zswap_writeback_entry() have the same part that
decompress the data from zswap_entry to page, so refactor out the
common part as __zswap_load(entry, page).

Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
---
 mm/zswap.c | 107 ++++++++++++++++++++++---------------------------------------
 1 file changed, 38 insertions(+), 69 deletions(-)

diff --git a/mm/zswap.c b/mm/zswap.c
index fa186945010d..2f095c919a5c 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -1392,6 +1392,41 @@ static int zswap_enabled_param_set(const char *val,
 	return ret;
 }
 
+static void __zswap_load(struct zswap_entry *entry, struct page *page)
+{
+	struct scatterlist input, output;
+	unsigned int dlen = PAGE_SIZE;
+	struct crypto_acomp_ctx *acomp_ctx;
+	struct zpool *zpool;
+	u8 *src;
+	int ret;
+
+	acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
+	mutex_lock(acomp_ctx->mutex);
+
+	zpool = zswap_find_zpool(entry);
+	src = zpool_map_handle(zpool, entry->handle, ZPOOL_MM_RO);
+	if (!zpool_can_sleep_mapped(zpool)) {
+		memcpy(acomp_ctx->dstmem, src, entry->length);
+		src = acomp_ctx->dstmem;
+		zpool_unmap_handle(zpool, entry->handle);
+	}
+
+	sg_init_one(&input, src, entry->length);
+	sg_init_table(&output, 1);
+	sg_set_page(&output, page, PAGE_SIZE, 0);
+	acomp_request_set_params(acomp_ctx->req, &input, &output, entry->length, dlen);
+	ret = crypto_wait_req(crypto_acomp_decompress(acomp_ctx->req), &acomp_ctx->wait);
+	dlen = acomp_ctx->req->dlen;
+	mutex_unlock(acomp_ctx->mutex);
+
+	if (zpool_can_sleep_mapped(zpool))
+		zpool_unmap_handle(zpool, entry->handle);
+
+	BUG_ON(ret);
+	BUG_ON(dlen != PAGE_SIZE);
+}
+
 /*********************************
 * writeback code
 **********************************/
@@ -1413,23 +1448,12 @@ static int zswap_writeback_entry(struct zswap_entry *entry,
 	swp_entry_t swpentry = entry->swpentry;
 	struct page *page;
 	struct mempolicy *mpol;
-	struct scatterlist input, output;
-	struct crypto_acomp_ctx *acomp_ctx;
-	struct zpool *pool = zswap_find_zpool(entry);
 	bool page_was_allocated;
-	u8 *src, *tmp = NULL;
-	unsigned int dlen;
 	int ret;
 	struct writeback_control wbc = {
 		.sync_mode = WB_SYNC_NONE,
 	};
 
-	if (!zpool_can_sleep_mapped(pool)) {
-		tmp = kmalloc(PAGE_SIZE, GFP_KERNEL);
-		if (!tmp)
-			return -ENOMEM;
-	}
-
 	/* try to allocate swap cache page */
 	mpol = get_task_policy(current);
 	page = __read_swap_cache_async(swpentry, GFP_KERNEL, mpol,
@@ -1462,33 +1486,7 @@ static int zswap_writeback_entry(struct zswap_entry *entry,
 	}
 	spin_unlock(&tree->lock);
 
-	/* decompress */
-	acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
-	dlen = PAGE_SIZE;
-
-	src = zpool_map_handle(pool, entry->handle, ZPOOL_MM_RO);
-	if (!zpool_can_sleep_mapped(pool)) {
-		memcpy(tmp, src, entry->length);
-		src = tmp;
-		zpool_unmap_handle(pool, entry->handle);
-	}
-
-	mutex_lock(acomp_ctx->mutex);
-	sg_init_one(&input, src, entry->length);
-	sg_init_table(&output, 1);
-	sg_set_page(&output, page, PAGE_SIZE, 0);
-	acomp_request_set_params(acomp_ctx->req, &input, &output, entry->length, dlen);
-	ret = crypto_wait_req(crypto_acomp_decompress(acomp_ctx->req), &acomp_ctx->wait);
-	dlen = acomp_ctx->req->dlen;
-	mutex_unlock(acomp_ctx->mutex);
-
-	if (!zpool_can_sleep_mapped(pool))
-		kfree(tmp);
-	else
-		zpool_unmap_handle(pool, entry->handle);
-
-	BUG_ON(ret);
-	BUG_ON(dlen != PAGE_SIZE);
+	__zswap_load(entry, page);
 
 	/* page is up to date */
 	SetPageUptodate(page);
@@ -1508,9 +1506,6 @@ static int zswap_writeback_entry(struct zswap_entry *entry,
 	return ret;
 
 fail:
-	if (!zpool_can_sleep_mapped(pool))
-		kfree(tmp);
-
 	/*
 	 * If we get here because the page is already in swapcache, a
 	 * load may be happening concurrently. It is safe and okay to
@@ -1769,11 +1764,7 @@ bool zswap_load(struct folio *folio)
 	struct page *page = &folio->page;
 	struct zswap_tree *tree = zswap_trees[type];
 	struct zswap_entry *entry;
-	struct scatterlist input, output;
-	struct crypto_acomp_ctx *acomp_ctx;
-	unsigned int dlen = PAGE_SIZE;
-	u8 *src, *dst;
-	struct zpool *zpool;
+	u8 *dst;
 	bool ret;
 
 	VM_WARN_ON_ONCE(!folio_test_locked(folio));
@@ -1795,29 +1786,7 @@ bool zswap_load(struct folio *folio)
 		goto stats;
 	}
 
-	/* decompress */
-	acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
-	mutex_lock(acomp_ctx->mutex);
-
-	zpool = zswap_find_zpool(entry);
-	src = zpool_map_handle(zpool, entry->handle, ZPOOL_MM_RO);
-	if (!zpool_can_sleep_mapped(zpool)) {
-		memcpy(acomp_ctx->dstmem, src, entry->length);
-		src = acomp_ctx->dstmem;
-		zpool_unmap_handle(zpool, entry->handle);
-	}
-
-	sg_init_one(&input, src, entry->length);
-	sg_init_table(&output, 1);
-	sg_set_page(&output, page, PAGE_SIZE, 0);
-	acomp_request_set_params(acomp_ctx->req, &input, &output, entry->length, dlen);
-	if (crypto_wait_req(crypto_acomp_decompress(acomp_ctx->req), &acomp_ctx->wait))
-		WARN_ON(1);
-	mutex_unlock(acomp_ctx->mutex);
-
-	if (zpool_can_sleep_mapped(zpool))
-		zpool_unmap_handle(zpool, entry->handle);
-
+	__zswap_load(entry, page);
 	ret = true;
 stats:
 	count_vm_event(ZSWPIN);

-- 
b4 0.10.1

On Tue, Dec 12, 2023 at 8:18 PM Chengming Zhou
<zhouchengming@bytedance.com> wrote:
>
> The zswap_load() and zswap_writeback_entry() have the same part that
> decompress the data from zswap_entry to page, so refactor out the
> common part as __zswap_load(entry, page).
>
> Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
> Reviewed-by: Nhat Pham <nphamcs@gmail.com>

On a second look, there a few nits here.

First I think it makes more sense to move this refactoring ahead of
reusing destmem. Right now, we add the destmem reuse to zswap_load()
only, then we do the refactor and zswap_writeback_entry() gets it
automatically, so there is a slight change coming to
zswap_writeback_entry() hidden in the refactoring patch.

Let's refactor out __zswap_load() first, then reuse destmem in it.

> ---
>  mm/zswap.c | 107 ++++++++++++++++++++++---------------------------------------
>  1 file changed, 38 insertions(+), 69 deletions(-)
>
> diff --git a/mm/zswap.c b/mm/zswap.c
> index fa186945010d..2f095c919a5c 100644
> --- a/mm/zswap.c
> +++ b/mm/zswap.c
> @@ -1392,6 +1392,41 @@ static int zswap_enabled_param_set(const char *val,
>         return ret;
>  }
>
> +static void __zswap_load(struct zswap_entry *entry, struct page *page)
> +{
> +       struct scatterlist input, output;
> +       unsigned int dlen = PAGE_SIZE;
> +       struct crypto_acomp_ctx *acomp_ctx;
> +       struct zpool *zpool;
> +       u8 *src;
> +       int ret;
> +
> +       acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
> +       mutex_lock(acomp_ctx->mutex);
> +
> +       zpool = zswap_find_zpool(entry);
> +       src = zpool_map_handle(zpool, entry->handle, ZPOOL_MM_RO);
> +       if (!zpool_can_sleep_mapped(zpool)) {
> +               memcpy(acomp_ctx->dstmem, src, entry->length);
> +               src = acomp_ctx->dstmem;
> +               zpool_unmap_handle(zpool, entry->handle);
> +       }
> +
> +       sg_init_one(&input, src, entry->length);
> +       sg_init_table(&output, 1);
> +       sg_set_page(&output, page, PAGE_SIZE, 0);
> +       acomp_request_set_params(acomp_ctx->req, &input, &output, entry->length, dlen);

We should pass PAGE_SIZE here directly, BUG_ON(acomp_ctx->req->dlen)
below, and remove the dlen variable.

> +       ret = crypto_wait_req(crypto_acomp_decompress(acomp_ctx->req), &acomp_ctx->wait);

We should just BUG_ON() here directly an remove the ret variable.

On 2023/12/14 08:52, Yosry Ahmed wrote:
> On Tue, Dec 12, 2023 at 8:18 PM Chengming Zhou
> <zhouchengming@bytedance.com> wrote:
>>
>> The zswap_load() and zswap_writeback_entry() have the same part that
>> decompress the data from zswap_entry to page, so refactor out the
>> common part as __zswap_load(entry, page).
>>
>> Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
>> Reviewed-by: Nhat Pham <nphamcs@gmail.com>
> 
> On a second look, there a few nits here.
> 
> First I think it makes more sense to move this refactoring ahead of
> reusing destmem. Right now, we add the destmem reuse to zswap_load()
> only, then we do the refactor and zswap_writeback_entry() gets it
> automatically, so there is a slight change coming to
> zswap_writeback_entry() hidden in the refactoring patch.
> 
> Let's refactor out __zswap_load() first, then reuse destmem in it.

I tried but found that putting the __zswap_load() first would introduce
another failure case in zswap_writeback_entry(), since the temporary
memory allocation may fail.

So instead, I also move the dstmem reusing in zswap_writeback_entry() to
the dstmem reusing patch. Then this patch becomes having only refactoring.

Thanks.

On Mon, Dec 18, 2023 at 12:15 AM Chengming Zhou
<zhouchengming@bytedance.com> wrote:
>
> On 2023/12/14 08:52, Yosry Ahmed wrote:
> > On Tue, Dec 12, 2023 at 8:18 PM Chengming Zhou
> > <zhouchengming@bytedance.com> wrote:
> >>
> >> The zswap_load() and zswap_writeback_entry() have the same part that
> >> decompress the data from zswap_entry to page, so refactor out the
> >> common part as __zswap_load(entry, page).
> >>
> >> Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
> >> Reviewed-by: Nhat Pham <nphamcs@gmail.com>
> >
> > On a second look, there a few nits here.
> >
> > First I think it makes more sense to move this refactoring ahead of
> > reusing destmem. Right now, we add the destmem reuse to zswap_load()
> > only, then we do the refactor and zswap_writeback_entry() gets it
> > automatically, so there is a slight change coming to
> > zswap_writeback_entry() hidden in the refactoring patch.
> >
> > Let's refactor out __zswap_load() first, then reuse destmem in it.
>
> I tried but found that putting the __zswap_load() first would introduce
> another failure case in zswap_writeback_entry(), since the temporary
> memory allocation may fail.
>
> So instead, I also move the dstmem reusing in zswap_writeback_entry() to
> the dstmem reusing patch. Then this patch becomes having only refactoring.

We could have still refactored __zswap_load() first by making it
return an int initially when split, then void later. Anyway, it's not
a big deal. The new series looks fine.

On 2023/12/14 08:52, Yosry Ahmed wrote:
> On Tue, Dec 12, 2023 at 8:18 PM Chengming Zhou
> <zhouchengming@bytedance.com> wrote:
>>
>> The zswap_load() and zswap_writeback_entry() have the same part that
>> decompress the data from zswap_entry to page, so refactor out the
>> common part as __zswap_load(entry, page).
>>
>> Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
>> Reviewed-by: Nhat Pham <nphamcs@gmail.com>
> 
> On a second look, there a few nits here.
> 
> First I think it makes more sense to move this refactoring ahead of
> reusing destmem. Right now, we add the destmem reuse to zswap_load()
> only, then we do the refactor and zswap_writeback_entry() gets it
> automatically, so there is a slight change coming to
> zswap_writeback_entry() hidden in the refactoring patch.
> 
> Let's refactor out __zswap_load() first, then reuse destmem in it.
> 

Ok, will put it first.

>> ---
>>  mm/zswap.c | 107 ++++++++++++++++++++++---------------------------------------
>>  1 file changed, 38 insertions(+), 69 deletions(-)
>>
>> diff --git a/mm/zswap.c b/mm/zswap.c
>> index fa186945010d..2f095c919a5c 100644
>> --- a/mm/zswap.c
>> +++ b/mm/zswap.c
>> @@ -1392,6 +1392,41 @@ static int zswap_enabled_param_set(const char *val,
>>         return ret;
>>  }
>>
>> +static void __zswap_load(struct zswap_entry *entry, struct page *page)
>> +{
>> +       struct scatterlist input, output;
>> +       unsigned int dlen = PAGE_SIZE;
>> +       struct crypto_acomp_ctx *acomp_ctx;
>> +       struct zpool *zpool;
>> +       u8 *src;
>> +       int ret;
>> +
>> +       acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
>> +       mutex_lock(acomp_ctx->mutex);
>> +
>> +       zpool = zswap_find_zpool(entry);
>> +       src = zpool_map_handle(zpool, entry->handle, ZPOOL_MM_RO);
>> +       if (!zpool_can_sleep_mapped(zpool)) {
>> +               memcpy(acomp_ctx->dstmem, src, entry->length);
>> +               src = acomp_ctx->dstmem;
>> +               zpool_unmap_handle(zpool, entry->handle);
>> +       }
>> +
>> +       sg_init_one(&input, src, entry->length);
>> +       sg_init_table(&output, 1);
>> +       sg_set_page(&output, page, PAGE_SIZE, 0);
>> +       acomp_request_set_params(acomp_ctx->req, &input, &output, entry->length, dlen);
> 
> We should pass PAGE_SIZE here directly, BUG_ON(acomp_ctx->req->dlen)
> below, and remove the dlen variable.
> 
>> +       ret = crypto_wait_req(crypto_acomp_decompress(acomp_ctx->req), &acomp_ctx->wait);
> 
> We should just BUG_ON() here directly an remove the ret variable.

Ok, thanks!

On Tue, Dec 12, 2023 at 8:18 PM Chengming Zhou
<zhouchengming@bytedance.com> wrote:
>
> The zswap_load() and zswap_writeback_entry() have the same part that
> decompress the data from zswap_entry to page, so refactor out the
> common part as __zswap_load(entry, page).
>
> Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
> Reviewed-by: Nhat Pham <nphamcs@gmail.com>

Great cleanup,
Reviewed-by: Yosry Ahmed <yosryahmed@google.com>