gfs2: Don't pack struct lm_lockname

As per a suggestion by Linus, don't pack struct lm_lockname: we did that
because the struct is used as a rhashtable key, but packing tells the
compiler that the 64-bit fields in the struct may be unaligned, causing
it to generate worse code on some architectures.  Instead, rearrange the
fields in the struct so that there is no padding between fields, and
exclude any tail padding from the hash key size.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>

diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index b2638d8a24590461ada465771d07fc05c77a99af..35f3b0a1d81b30585a3d2da3759eab7fb2f0fdb6 100644 (file)
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -73,7 +73,7 @@ static DEFINE_SPINLOCK(lru_lock);
 
 static struct rhashtable_params ht_parms = {
        .nelem_hint = GFS2_GL_HASH_SIZE * 3 / 4,
-       .key_len = sizeof(struct lm_lockname),
+       .key_len = offsetofend(struct lm_lockname, ln_type),
        .key_offset = offsetof(struct gfs2_glock, gl_name),
        .head_offset = offsetof(struct gfs2_glock, gl_node),
 };

diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index 511e1ed7e2ded7b0a9dc9882cffe0b66c37c96a2..b7cf65d13561fedf98a72dfc66b36e70d84100cd 100644 (file)
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -203,11 +203,15 @@ enum {
        DFL_DLM_RECOVERY        = 6,
 };
 
+/*
+ * We are using struct lm_lockname as an rhashtable key.  Avoid holes within
+ * the struct; padding at the end is fine.
+ */
 struct lm_lockname {
-       struct gfs2_sbd *ln_sbd;
        u64 ln_number;
+       struct gfs2_sbd *ln_sbd;
        unsigned int ln_type;
-} __packed __aligned(sizeof(int));
+};
 
 #define lm_name_equal(name1, name2) \
         (((name1)->ln_number == (name2)->ln_number) && \