NFS: Replace readdir's use of xxhash() with hash_64()
Both xxhash() and hash_64() appear to give similarly low collision
rates with a standard linearly increasing readdir offset. They both give
similarly higher collision rates when applied to ext4's offsets.
So switch to using the standard hash_64().
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
diff --git a/fs/nfs/Kconfig b/fs/nfs/Kconfig
index 47a53b3..14a7222 100644
--- a/fs/nfs/Kconfig
+++ b/fs/nfs/Kconfig
@@ -4,10 +4,6 @@
depends on INET && FILE_LOCKING && MULTIUSER
select LOCKD
select SUNRPC
- select CRYPTO
- select CRYPTO_HASH
- select XXHASH
- select CRYPTO_XXHASH
select NFS_ACL_SUPPORT if NFS_V3_ACL
help
Choose Y here if you want to access files residing on other
diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 0365063..c6b263b 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -39,7 +39,7 @@
#include <linux/sched.h>
#include <linux/kmemleak.h>
#include <linux/xattr.h>
-#include <linux/xxhash.h>
+#include <linux/hash.h>
#include "delegation.h"
#include "iostat.h"
@@ -350,10 +350,7 @@ static int nfs_readdir_page_array_append(struct page *page,
* of directory cookies. Content is addressed by the value of the
* cookie index of the first readdir entry in a page.
*
- * The xxhash algorithm is chosen because it is fast, and is supposed
- * to result in a decent flat distribution of hashes.
- *
- * We then select only the first 18 bits to avoid issues with excessive
+ * We select only the first 18 bits to avoid issues with excessive
* memory use for the page cache XArray. 18 bits should allow the caching
* of 262144 pages of sequences of readdir entries. Since each page holds
* 127 readdir entries for a typical 64-bit system, that works out to a
@@ -363,7 +360,7 @@ static pgoff_t nfs_readdir_page_cookie_hash(u64 cookie)
{
if (cookie == 0)
return 0;
- return xxhash(&cookie, sizeof(cookie), 0) & NFS_READDIR_COOKIE_MASK;
+ return hash_64(cookie, 18);
}
static bool nfs_readdir_page_validate(struct page *page, u64 last_cookie,
