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authorVitaly Wool <vitalywool@gmail.com>2019-09-24 01:39:43 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2019-09-25 01:54:12 +0300
commit068619e32ff6229a09407d267e36ea7710b96ea1 (patch)
treeea940e56669826675ee347d6b2e11c298044e5e7 /mm
parentd2fcd82bb83aab47c6d63aa8c960cd5edb578065 (diff)
downloadlinux-068619e32ff6229a09407d267e36ea7710b96ea1.tar.xz
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 <vitalywool@gmail.com> Reviewed-by: Dan Streetman <ddstreet@ieee.org> Cc: Shakeel Butt <shakeelb@google.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> Cc: Seth Jennings <sjenning@redhat.com> Cc: Vitaly Wool <vitalywool@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/zswap.c7
1 files 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 @@ fail:
spin_unlock(&tree->lock);
end:
+ zpool_unmap_handle(pool, handle);
return ret;
}