fuse: reduce size of struct fuse_inode

Do this by grouping fields used for cached writes and putting them into a
union with fileds used for cached readdir (with obviously no overlap, since
we don't have hybrid objects).
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fs/fuse/dir.c

@@ -1414,8 +1414,11 @@ int fuse_do_setattr(struct dentry *dentry, struct iattr *attr,
 		file = NULL;
 	}
 
-	if (attr->ia_valid & ATTR_SIZE)
+	if (attr->ia_valid & ATTR_SIZE) {
+		if (WARN_ON(!S_ISREG(inode->i_mode)))
+			return -EIO;
 		is_truncate = true;
+	}
 
 	if (is_truncate) {
 		fuse_set_nowrite(inode);
@@ -1619,8 +1622,16 @@ void fuse_init_common(struct inode *inode)
 
 void fuse_init_dir(struct inode *inode)
 {
+	struct fuse_inode *fi = get_fuse_inode(inode);
+
 	inode->i_op = &fuse_dir_inode_operations;
 	inode->i_fop = &fuse_dir_operations;
+
+	spin_lock_init(&fi->rdc.lock);
+	fi->rdc.cached = false;
+	fi->rdc.size = 0;
+	fi->rdc.pos = 0;
+	fi->rdc.version = 0;
 }
 
 void fuse_init_symlink(struct inode *inode)

fs/fuse/file.c

@@ -3143,6 +3143,14 @@ static const struct address_space_operations fuse_file_aops  = {
 
 void fuse_init_file_inode(struct inode *inode)
 {
+	struct fuse_inode *fi = get_fuse_inode(inode);
+
 	inode->i_fop = &fuse_file_operations;
 	inode->i_data.a_ops = &fuse_file_aops;
+
+	INIT_LIST_HEAD(&fi->write_files);
+	INIT_LIST_HEAD(&fi->queued_writes);
+	fi->writectr = 0;
+	init_waitqueue_head(&fi->page_waitq);
+	INIT_LIST_HEAD(&fi->writepages);
 }

fs/fuse/fuse_i.h

@@ -87,45 +87,51 @@ struct fuse_inode {
 	/** Version of last attribute change */
 	u64 attr_version;
 
-	/** Files usable in writepage.  Protected by fc->lock */
-	struct list_head write_files;
+	union {
+		/* Write related fields (regular file only) */
+		struct {
+			/* Files usable in writepage.  Protected by fc->lock */
+			struct list_head write_files;
 
-	/** Writepages pending on truncate or fsync */
-	struct list_head queued_writes;
+			/* Writepages pending on truncate or fsync */
+			struct list_head queued_writes;
 
-	/** Number of sent writes, a negative bias (FUSE_NOWRITE)
-	 * means more writes are blocked */
-	int writectr;
+			/* Number of sent writes, a negative bias
+			 * (FUSE_NOWRITE) means more writes are blocked */
+			int writectr;
 
-	/** Waitq for writepage completion */
-	wait_queue_head_t page_waitq;
+			/* Waitq for writepage completion */
+			wait_queue_head_t page_waitq;
 
-	/** List of writepage requestst (pending or sent) */
-	struct list_head writepages;
+			/* List of writepage requestst (pending or sent) */
+			struct list_head writepages;
+		};
 
-	/* readdir cache */
-	struct {
-		/* true if fully cached */
-		bool cached;
+		/* readdir cache (directory only) */
+		struct {
+			/* true if fully cached */
+			bool cached;
 
-		/* size of cache */
-		loff_t size;
+			/* size of cache */
+			loff_t size;
 
-		/* position at end of cache (position of next entry) */
-		loff_t pos;
+			/* position at end of cache (position of next entry) */
+			loff_t pos;
 
-		/* version of the cache */
-		u64 version;
+			/* version of the cache */
+			u64 version;
 
-		/* modification time of directory when cache was started */
-		struct timespec64 mtime;
+			/* modification time of directory when cache was
+			 * started */
+			struct timespec64 mtime;
 
-		/* iversion of directory when cache was started */
-		u64 iversion;
+			/* iversion of directory when cache was started */
+			u64 iversion;
 
-		/* protects above fields */
-		spinlock_t lock;
-	} rdc;
+			/* protects above fields */
+			spinlock_t lock;
+		} rdc;
+	};
 
 	/** Miscellaneous bits describing inode state */
 	unsigned long state;

fs/fuse/inode.c

@@ -93,18 +93,8 @@ static struct inode *fuse_alloc_inode(struct super_block *sb)
 	fi->nodeid = 0;
 	fi->nlookup = 0;
 	fi->attr_version = 0;
-	fi->writectr = 0;
 	fi->orig_ino = 0;
 	fi->state = 0;
-	INIT_LIST_HEAD(&fi->write_files);
-	INIT_LIST_HEAD(&fi->queued_writes);
-	INIT_LIST_HEAD(&fi->writepages);
-	init_waitqueue_head(&fi->page_waitq);
-	spin_lock_init(&fi->rdc.lock);
-	fi->rdc.cached = false;
-	fi->rdc.size = 0;
-	fi->rdc.pos = 0;
-	fi->rdc.version = 0;
 	mutex_init(&fi->mutex);
 	fi->forget = fuse_alloc_forget();
 	if (!fi->forget) {
@@ -124,8 +114,10 @@ static void fuse_i_callback(struct rcu_head *head)
 static void fuse_destroy_inode(struct inode *inode)
 {
 	struct fuse_inode *fi = get_fuse_inode(inode);
-	BUG_ON(!list_empty(&fi->write_files));
-	BUG_ON(!list_empty(&fi->queued_writes));
+	if (S_ISREG(inode->i_mode)) {
+		WARN_ON(!list_empty(&fi->write_files));
+		WARN_ON(!list_empty(&fi->queued_writes));
+	}
 	mutex_destroy(&fi->mutex);
 	kfree(fi->forget);
 	call_rcu(&inode->i_rcu, fuse_i_callback);