gfs2: Use container_of() for gfs2_glock(aspace)

Clang's structure layout randomization feature gets upset when it sees
struct address_space (which is randomized) cast to struct gfs2_glock.
This is due to seeing the mapping pointer as being treated as an array
of gfs2_glock, rather than "something else, before struct address_space":

In file included from fs/gfs2/acl.c:23:
fs/gfs2/meta_io.h:44:12: error: casting from randomized structure pointer type 'struct address_space *' to 'struct gfs2_glock *'
	return (((struct gfs2_glock *)mapping) - 1)->gl_name.ln_sbd;
		^

Replace the instances of open-coded pointer math with container_of()
usage, and update the allocator to match.

Some cleanups and conversion of gfs2_glock_get() and
gfs2_glock_dealloc() by Andreas.
Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/lkml/202205041550.naKxwCBj-lkp@intel.com
Cc: Bob Peterson <rpeterso@redhat.com>
Cc: Andreas Gruenbacher <agruenba@redhat.com>
Cc: Bill Wendling <morbo@google.com>
Cc: cluster-devel@redhat.com
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

fs/gfs2/glock.c

@@ -127,9 +127,11 @@ static void gfs2_glock_dealloc(struct rcu_head *rcu)
 	struct gfs2_glock *gl = container_of(rcu, struct gfs2_glock, gl_rcu);
 
 	kfree(gl->gl_lksb.sb_lvbptr);
-	if (gl->gl_ops->go_flags & GLOF_ASPACE)
-		kmem_cache_free(gfs2_glock_aspace_cachep, gl);
-	else
+	if (gl->gl_ops->go_flags & GLOF_ASPACE) {
+		struct gfs2_glock_aspace *gla =
+			container_of(gl, struct gfs2_glock_aspace, glock);
+		kmem_cache_free(gfs2_glock_aspace_cachep, gla);
+	} else
 		kmem_cache_free(gfs2_glock_cachep, gl);
 }
 
@@ -1159,7 +1161,6 @@ int gfs2_glock_get(struct gfs2_sbd *sdp, u64 number,
 				    .ln_sbd = sdp };
 	struct gfs2_glock *gl, *tmp;
 	struct address_space *mapping;
-	struct kmem_cache *cachep;
 	int ret = 0;
 
 	gl = find_insert_glock(&name, NULL);
@@ -1170,20 +1171,24 @@ int gfs2_glock_get(struct gfs2_sbd *sdp, u64 number,
 	if (!create)
 		return -ENOENT;
 
-	if (glops->go_flags & GLOF_ASPACE)
-		cachep = gfs2_glock_aspace_cachep;
-	else
-		cachep = gfs2_glock_cachep;
-	gl = kmem_cache_alloc(cachep, GFP_NOFS);
+	if (glops->go_flags & GLOF_ASPACE) {
+		struct gfs2_glock_aspace *gla =
+			kmem_cache_alloc(gfs2_glock_aspace_cachep, GFP_NOFS);
+		if (!gla)
+			return -ENOMEM;
+		gl = &gla->glock;
+	} else {
+		gl = kmem_cache_alloc(gfs2_glock_cachep, GFP_NOFS);
 		if (!gl)
 			return -ENOMEM;
-
+	}
 	memset(&gl->gl_lksb, 0, sizeof(struct dlm_lksb));
+	gl->gl_ops = glops;
 
 	if (glops->go_flags & GLOF_LVB) {
 		gl->gl_lksb.sb_lvbptr = kzalloc(GDLM_LVB_SIZE, GFP_NOFS);
 		if (!gl->gl_lksb.sb_lvbptr) {
-			kmem_cache_free(cachep, gl);
+			gfs2_glock_dealloc(&gl->gl_rcu);
 			return -ENOMEM;
 		}
 	}
@@ -1197,7 +1202,6 @@ int gfs2_glock_get(struct gfs2_sbd *sdp, u64 number,
 	gl->gl_state = LM_ST_UNLOCKED;
 	gl->gl_target = LM_ST_UNLOCKED;
 	gl->gl_demote_state = LM_ST_EXCLUSIVE;
-	gl->gl_ops = glops;
 	gl->gl_dstamp = 0;
 	preempt_disable();
 	/* We use the global stats to estimate the initial per-glock stats */
@@ -1234,8 +1238,7 @@ int gfs2_glock_get(struct gfs2_sbd *sdp, u64 number,
 	*glp = tmp;
 
 out_free:
-	kfree(gl->gl_lksb.sb_lvbptr);
-	kmem_cache_free(cachep, gl);
+	gfs2_glock_dealloc(&gl->gl_rcu);
 	if (atomic_dec_and_test(&sdp->sd_glock_disposal))
 		wake_up(&sdp->sd_glock_wait);
 

fs/gfs2/glock.h

@@ -138,6 +138,11 @@ struct lm_lockops {
 	const match_table_t *lm_tokens;
 };
 
+struct gfs2_glock_aspace {
+	struct gfs2_glock glock;
+	struct address_space mapping;
+};
+
 extern struct workqueue_struct *gfs2_delete_workqueue;
 static inline struct gfs2_holder *gfs2_glock_is_locked_by_me(struct gfs2_glock *gl)
 {
@@ -179,8 +184,11 @@ static inline int gfs2_glock_is_held_shrd(struct gfs2_glock *gl)
 
 static inline struct address_space *gfs2_glock2aspace(struct gfs2_glock *gl)
 {
-	if (gl->gl_ops->go_flags & GLOF_ASPACE)
-		return (struct address_space *)(gl + 1);
+	if (gl->gl_ops->go_flags & GLOF_ASPACE) {
+		struct gfs2_glock_aspace *gla =
+			container_of(gl, struct gfs2_glock_aspace, glock);
+		return &gla->mapping;
+	}
 	return NULL;
 }
 

fs/gfs2/main.c

@@ -62,11 +62,10 @@ static void gfs2_init_glock_once(void *foo)
 
 static void gfs2_init_gl_aspace_once(void *foo)
 {
-	struct gfs2_glock *gl = foo;
-	struct address_space *mapping = (struct address_space *)(gl + 1);
+	struct gfs2_glock_aspace *gla = foo;
 
-	gfs2_init_glock_once(gl);
-	address_space_init_once(mapping);
+	gfs2_init_glock_once(&gla->glock);
+	address_space_init_once(&gla->mapping);
 }
 
 /**
@@ -104,8 +103,7 @@ static int __init init_gfs2_fs(void)
 		goto fail_cachep1;
 
 	gfs2_glock_aspace_cachep = kmem_cache_create("gfs2_glock(aspace)",
-					sizeof(struct gfs2_glock) +
-					sizeof(struct address_space),
+					sizeof(struct gfs2_glock_aspace),
 					0, 0, gfs2_init_gl_aspace_once);
 
 	if (!gfs2_glock_aspace_cachep)

fs/gfs2/meta_io.h

@@ -40,9 +40,11 @@ extern const struct address_space_operations gfs2_rgrp_aops;
 static inline struct gfs2_sbd *gfs2_mapping2sbd(struct address_space *mapping)
 {
 	struct inode *inode = mapping->host;
-	if (mapping->a_ops == &gfs2_meta_aops)
-		return (((struct gfs2_glock *)mapping) - 1)->gl_name.ln_sbd;
-	else if (mapping->a_ops == &gfs2_rgrp_aops)
+	if (mapping->a_ops == &gfs2_meta_aops) {
+		struct gfs2_glock_aspace *gla =
+			container_of(mapping, struct gfs2_glock_aspace, mapping);
+		return gla->glock.gl_name.ln_sbd;
+	} else if (mapping->a_ops == &gfs2_rgrp_aops)
 		return container_of(mapping, struct gfs2_sbd, sd_aspace);
 	else
 		return inode->i_sb->s_fs_info;