zswap: only save zswap header when necessary
We waste sizeof(swp_entry_t) for zswap header when using zsmalloc as
zpool driver because zsmalloc doesn't support eviction.
Add zpool_evictable() to detect if zpool is potentially evictable, and
use it in zswap to avoid waste memory for zswap header.
[yuzhao@google.com: The zpool->" prefix is a result of copy & paste]
Link: http://lkml.kernel.org/r/20180110225626.110330-1-yuzhao@google.com
Link: http://lkml.kernel.org/r/20180110224741.83751-1-yuzhao@google.com
Signed-off-by: Yu Zhao <yuzhao@google.com>
Acked-by: Dan Streetman <ddstreet@ieee.org>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/zswap.c b/mm/zswap.c
index 1133b4ce..c004aa4 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -1001,11 +1001,11 @@
struct zswap_entry *entry, *dupentry;
struct crypto_comp *tfm;
int ret;
- unsigned int dlen = PAGE_SIZE, len;
+ unsigned int hlen, dlen = PAGE_SIZE;
unsigned long handle, value;
char *buf;
u8 *src, *dst;
- struct zswap_header *zhdr;
+ struct zswap_header zhdr = { .swpentry = swp_entry(type, offset) };
if (!zswap_enabled || !tree) {
ret = -ENODEV;
@@ -1063,8 +1063,8 @@
}
/* store */
- len = dlen + sizeof(struct zswap_header);
- ret = zpool_malloc(entry->pool->zpool, len,
+ hlen = zpool_evictable(entry->pool->zpool) ? sizeof(zhdr) : 0;
+ ret = zpool_malloc(entry->pool->zpool, hlen + dlen,
__GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM,
&handle);
if (ret == -ENOSPC) {
@@ -1075,10 +1075,9 @@
zswap_reject_alloc_fail++;
goto put_dstmem;
}
- zhdr = zpool_map_handle(entry->pool->zpool, handle, ZPOOL_MM_RW);
- zhdr->swpentry = swp_entry(type, offset);
- buf = (u8 *)(zhdr + 1);
- memcpy(buf, dst, dlen);
+ buf = zpool_map_handle(entry->pool->zpool, handle, ZPOOL_MM_RW);
+ memcpy(buf, &zhdr, hlen);
+ memcpy(buf + hlen, dst, dlen);
zpool_unmap_handle(entry->pool->zpool, handle);
put_cpu_var(zswap_dstmem);
@@ -1149,8 +1148,9 @@
/* decompress */
dlen = PAGE_SIZE;
- src = (u8 *)zpool_map_handle(entry->pool->zpool, entry->handle,
- ZPOOL_MM_RO) + sizeof(struct zswap_header);
+ src = zpool_map_handle(entry->pool->zpool, entry->handle, ZPOOL_MM_RO);
+ if (zpool_evictable(entry->pool->zpool))
+ src += sizeof(struct zswap_header);
dst = kmap_atomic(page);
tfm = *get_cpu_ptr(entry->pool->tfm);
ret = crypto_comp_decompress(tfm, src, entry->length, dst, &dlen);