On 2023/12/14 07:24, Yosry Ahmed wrote:
> On Tue, Dec 12, 2023 at 8:18 PM Chengming Zhou
> <zhouchengming@xxxxxxxxxxxxx> wrote:
>>
>> In the !zpool_can_sleep_mapped() case such as zsmalloc, we need to first
>> copy the entry->handle memory to a temporary memory, which is allocated
>> using kmalloc.
>>
>> Obviously we can reuse the per-compressor dstmem to avoid allocating
>> every time, since it's percpu-compressor and protected in mutex.
>>
>> Signed-off-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
>> Reviewed-by: Nhat Pham <nphamcs@xxxxxxxxx>
>> ---
>> mm/zswap.c | 29 +++++++++--------------------
>> 1 file changed, 9 insertions(+), 20 deletions(-)
>>
>> diff --git a/mm/zswap.c b/mm/zswap.c
>> index 7ee54a3d8281..edb8b45ed5a1 100644
>> --- a/mm/zswap.c
>> +++ b/mm/zswap.c
>> @@ -1772,9 +1772,9 @@ bool zswap_load(struct folio *folio)
>> struct zswap_entry *entry;
>> struct scatterlist input, output;
>> struct crypto_acomp_ctx *acomp_ctx;
>> - u8 *src, *dst, *tmp;
>> + unsigned int dlen = PAGE_SIZE;
>> + u8 *src, *dst;
>> struct zpool *zpool;
>> - unsigned int dlen;
>> bool ret;
>>
>> VM_WARN_ON_ONCE(!folio_test_locked(folio));
>> @@ -1796,27 +1796,18 @@ bool zswap_load(struct folio *folio)
>> goto stats;
>> }
>>
>> - zpool = zswap_find_zpool(entry);
>> - if (!zpool_can_sleep_mapped(zpool)) {
>> - tmp = kmalloc(entry->length, GFP_KERNEL);
>> - if (!tmp) {
>> - ret = false;
>> - goto freeentry;
>> - }
>> - }
>> -
>> /* decompress */
>> - dlen = PAGE_SIZE;
>> - src = zpool_map_handle(zpool, entry->handle, ZPOOL_MM_RO);
>> + 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(tmp, src, entry->length);
>> - src = tmp;
>> + memcpy(acomp_ctx->dstmem, src, entry->length);
>> + src = acomp_ctx->dstmem;
>
> I don't like that we are now using acomp_ctx->dstmem and
> acomp_ctx->mutex now for purposes other than what the naming suggests.
The "mutex" name is coherent, "dstmem" depends on how we use IMHO.
Change to just "mem"? Or do you have a better name to replace?
>
> How about removing these two fields from acomp_ctx, and directly using
> zswap_dstmem and zswap_mutex in both the load and store paths, rename
> them, and add proper comments above their definitions that they are
> for generic percpu buffering on the load and store paths?
Yes, they are percpu memory and lock, but they are used by per acomp_ctx,
and the cpu maybe changing in the middle, so maybe better to keep them.
Thanks!
