From 068619e32ff6229a09407d267e36ea7710b96ea1 Mon Sep 17 00:00:00 2001 From: Vitaly Wool Date: Mon, 23 Sep 2019 15:39:43 -0700 Subject: [PATCH] zswap: do not map same object twice zswap_writeback_entry() maps a handle to read swpentry first, and then in the most common case it would map the same handle again. This is ok when zbud is the backend since its mapping callback is plain and simple, but it slows things down for z3fold. Since there's hardly a point in unmapping a handle _that_ fast as zswap_writeback_entry() does when it reads swpentry, the suggestion is to keep the handle mapped till the end. Link: http://lkml.kernel.org/r/20190916004640.b453167d3556c4093af4cf7d@gmail.com Signed-off-by: Vitaly Wool Reviewed-by: Dan Streetman Cc: Shakeel Butt Cc: Minchan Kim Cc: Sergey Senozhatsky Cc: Seth Jennings Cc: Vitaly Wool Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/zswap.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/mm/zswap.c b/mm/zswap.c index 08b6cefae5d8..46a322316e52 100644 --- a/mm/zswap.c +++ b/mm/zswap.c @@ -856,7 +856,6 @@ static int zswap_writeback_entry(struct zpool *pool, unsigned long handle) /* extract swpentry from data */ zhdr = zpool_map_handle(pool, handle, ZPOOL_MM_RO); swpentry = zhdr->swpentry; /* here */ - zpool_unmap_handle(pool, handle); tree = zswap_trees[swp_type(swpentry)]; offset = swp_offset(swpentry); @@ -866,6 +865,7 @@ static int zswap_writeback_entry(struct zpool *pool, unsigned long handle) if (!entry) { /* entry was invalidated */ spin_unlock(&tree->lock); + zpool_unmap_handle(pool, handle); return 0; } spin_unlock(&tree->lock); @@ -886,15 +886,13 @@ static int zswap_writeback_entry(struct zpool *pool, unsigned long handle) case ZSWAP_SWAPCACHE_NEW: /* page is locked */ /* decompress */ dlen = PAGE_SIZE; - src = (u8 *)zpool_map_handle(entry->pool->zpool, entry->handle, - ZPOOL_MM_RO) + sizeof(struct zswap_header); + src = (u8 *)zhdr + 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); put_cpu_ptr(entry->pool->tfm); kunmap_atomic(dst); - zpool_unmap_handle(entry->pool->zpool, entry->handle); BUG_ON(ret); BUG_ON(dlen != PAGE_SIZE); @@ -940,6 +938,7 @@ static int zswap_writeback_entry(struct zpool *pool, unsigned long handle) spin_unlock(&tree->lock); end: + zpool_unmap_handle(pool, handle); return ret; }