[RFC PATCH 40/76] cachefiles: Merge object->backer into object->dentry

[David Howells <dhowells@redhat.com>]

Merge the object->backer pointer into the object->dentry pointer and assume
that data objects are always going to be just regular files.

object->dentry can then more easily be overridden later by invalidation
without having two different things to update the xattrs on.

object->old maintains a pointer to the old file so that we can unlink the
it later.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/cachefiles/interface.c |   35 +++++++++++++++++------------------
 fs/cachefiles/internal.h  |    2 +-
 fs/cachefiles/io.c        |    4 ++--
 fs/cachefiles/namei.c     |    4 +++-
 4 files changed, 23 insertions(+), 22 deletions(-)

diff --git a/fs/cachefiles/interface.c b/fs/cachefiles/interface.c
index dc8c875223bb..7e8940a7fb55 100644
--- a/fs/cachefiles/interface.c
+++ b/fs/cachefiles/interface.c
@@ -171,16 +171,16 @@ static void cachefiles_update_object(struct fscache_object *_object)
 	cachefiles_begin_secure(cache, &saved_cred);
 
 	object_size = object->fscache.cookie->object_size;
-	if (i_size_read(d_inode(object->backer)) > object_size) {
+	if (i_size_read(d_inode(object->dentry)) > object_size) {
 		struct path path = {
 			.mnt	= cache->mnt,
-			.dentry	= object->backer
+			.dentry	= object->dentry
 		};
-		_debug("trunc %llx -> %llx", i_size_read(d_inode(object->backer)), object_size);
+		_debug("trunc %llx -> %llx", i_size_read(d_inode(object->dentry)), object_size);
 		ret = vfs_truncate(&path, object_size);
 		if (ret < 0) {
 			cachefiles_io_error_obj(object, "Trunc-to-size failed");
-			cachefiles_remove_object_xattr(cache, object->backer);
+			cachefiles_remove_object_xattr(cache, object->dentry);
 			goto out;
 		}
 	}
@@ -219,9 +219,8 @@ static void cachefiles_clean_up_object(struct cachefiles_object *object,
 		fput(object->backing_file);
 	object->backing_file = NULL;
 
-	if (object->backer != object->dentry)
-		dput(object->backer);
-	object->backer = NULL;
+	dput(object->old);
+	object->old = NULL;
 
 	cachefiles_unmark_inode_in_use(object, object->dentry);
 	dput(object->dentry);
@@ -295,7 +294,7 @@ static void cachefiles_put_object(struct fscache_object *_object,
 	if (u == 0) {
 		_debug("- kill object OBJ%x", object->fscache.debug_id);
 
-		ASSERTCMP(object->backer, ==, NULL);
+		ASSERTCMP(object->old, ==, NULL);
 		ASSERTCMP(object->dentry, ==, NULL);
 		ASSERTCMP(object->fscache.n_children, ==, 0);
 
@@ -360,17 +359,17 @@ static int cachefiles_attr_changed(struct cachefiles_object *object)
 	if (ni_size == object->i_size)
 		return 0;
 
-	if (!object->backer)
+	if (!object->dentry)
 		return -ENOBUFS;
 
-	ASSERT(d_is_reg(object->backer));
+	ASSERT(d_is_reg(object->dentry));
 
-	oi_size = i_size_read(d_backing_inode(object->backer));
+	oi_size = i_size_read(d_backing_inode(object->dentry));
 	if (oi_size == ni_size)
 		return 0;
 
 	cachefiles_begin_secure(cache, &saved_cred);
-	inode_lock(d_inode(object->backer));
+	inode_lock(d_inode(object->dentry));
 
 	/* if there's an extension to a partial page at the end of the backing
 	 * file, we need to discard the partial page so that we pick up new
@@ -379,17 +378,17 @@ static int cachefiles_attr_changed(struct cachefiles_object *object)
 		_debug("discard tail %llx", oi_size);
 		newattrs.ia_valid = ATTR_SIZE;
 		newattrs.ia_size = oi_size & PAGE_MASK;
-		ret = notify_change(object->backer, &newattrs, NULL);
+		ret = notify_change(object->dentry, &newattrs, NULL);
 		if (ret < 0)
 			goto truncate_failed;
 	}
 
 	newattrs.ia_valid = ATTR_SIZE;
 	newattrs.ia_size = ni_size;
-	ret = notify_change(object->backer, &newattrs, NULL);
+	ret = notify_change(object->dentry, &newattrs, NULL);
 
 truncate_failed:
-	inode_unlock(d_inode(object->backer));
+	inode_unlock(d_inode(object->dentry));
 	cachefiles_end_secure(cache, saved_cred);
 
 	if (ret == -EIO) {
@@ -422,10 +421,10 @@ static bool cachefiles_invalidate_object(struct fscache_object *_object)
 	_enter("{OBJ%x},[%llu]",
 	       object->fscache.debug_id, (unsigned long long)ni_size);
 
-	if (object->backer) {
-		ASSERT(d_is_reg(object->backer));
+	if (object->dentry) {
+		ASSERT(d_is_reg(object->dentry));
 
-		path.dentry = object->backer;
+		path.dentry = object->dentry;
 		path.mnt = cache->mnt;
 
 		cachefiles_begin_secure(cache, &saved_cred);
diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h
index caa6dfbaf333..2dab3ee386ad 100644
--- a/fs/cachefiles/internal.h
+++ b/fs/cachefiles/internal.h
@@ -35,7 +35,7 @@ extern unsigned cachefiles_debug;
 struct cachefiles_object {
 	struct fscache_object		fscache;	/* fscache handle */
 	struct dentry			*dentry;	/* the file/dir representing this object */
-	struct dentry			*backer;	/* backing file */
+	struct dentry			*old;		/* backing file */
 	struct file			*backing_file;	/* File open on backing storage */
 	loff_t				i_size;		/* object size */
 	atomic_t			usage;		/* object usage count */
diff --git a/fs/cachefiles/io.c b/fs/cachefiles/io.c
index f1d5976aa28c..2d406d681597 100644
--- a/fs/cachefiles/io.c
+++ b/fs/cachefiles/io.c
@@ -57,11 +57,11 @@ bool cachefiles_open_object(struct cachefiles_object *object)
 	struct path path;
 
 	path.mnt = cache->mnt;
-	path.dentry = object->backer;
+	path.dentry = object->dentry;
 
 	file = open_with_fake_path(&path,
 				   O_RDWR | O_LARGEFILE | O_DIRECT,
-				   d_backing_inode(object->backer),
+				   d_backing_inode(object->dentry),
 				   cache->cache_cred);
 	if (IS_ERR(file))
 		goto error;
diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c
index 4b515054d92e..9f6c91cff55d 100644
--- a/fs/cachefiles/namei.c
+++ b/fs/cachefiles/namei.c
@@ -486,7 +486,7 @@ bool cachefiles_walk_to_object(struct cachefiles_object *parent,
 				goto check_error;
 			}
 
-			object->backer = object->dentry;
+			object->old = dget(object->dentry);
 		} else {
 			BUG(); // TODO: open file in data-class subdir
 		}
@@ -521,7 +521,9 @@ bool cachefiles_walk_to_object(struct cachefiles_object *parent,
 		cachefiles_unmark_inode_in_use(object, object->dentry);
 	cachefiles_mark_object_inactive(cache, object);
 	dput(object->dentry);
+	dput(object->old);
 	object->dentry = NULL;
+	object->old = NULL;
 	goto error_out;
 
 lookup_error: