fuse: add blksize field to fuse_attr

There are cases when the filesystem will be passed the buffer from a single
read or write call, namely:

1) in 'direct-io' mode (not O_DIRECT), read/write requests don't go
through the page cache, but go directly to the userspace fs

2) currently buffered writes are done with single page requests, but
if Nick's ->perform_write() patch goes it, it will be possible to
do larger write requests. But only if the original write() was
also bigger than a page.

In these cases the filesystem might want to give a hint to the app
about the optimal I/O size.

Allow the userspace filesystem to supply a blksize value to be returned by
stat() and friends. If the field is zero, it defaults to the old
PAGE_CACHE_SIZE value.

Signed-off-by: Miklos Szeredi <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

fs/fuse/dir.c

···
 			     struct dentry *entry,
 			     struct fuse_entry_out *outarg)
 {
+	struct fuse_conn *fc = get_fuse_conn(dir);
+
+	memset(outarg, 0, sizeof(struct fuse_entry_out));
 	req->in.h.opcode = FUSE_LOOKUP;
 	req->in.h.nodeid = get_node_id(dir);
 	req->in.numargs = 1;
 	req->in.args[0].size = entry->d_name.len + 1;
 	req->in.args[0].value = entry->d_name.name;
 	req->out.numargs = 1;
-	req->out.args[0].size = sizeof(struct fuse_entry_out);
+	if (fc->minor < 9)
+		req->out.args[0].size = FUSE_COMPAT_ENTRY_OUT_SIZE;
+	else
+		req->out.args[0].size = sizeof(struct fuse_entry_out);
 	req->out.args[0].value = outarg;
 }
 
···
 
 	flags &= ~O_NOCTTY;
 	memset(&inarg, 0, sizeof(inarg));
+	memset(&outentry, 0, sizeof(outentry));
 	inarg.flags = flags;
 	inarg.mode = mode;
 	req->in.h.opcode = FUSE_CREATE;
···
 	req->in.args[1].size = entry->d_name.len + 1;
 	req->in.args[1].value = entry->d_name.name;
 	req->out.numargs = 2;
-	req->out.args[0].size = sizeof(outentry);
+	if (fc->minor < 9)
+		req->out.args[0].size = FUSE_COMPAT_ENTRY_OUT_SIZE;
+	else
+		req->out.args[0].size = sizeof(outentry);
 	req->out.args[0].value = &outentry;
 	req->out.args[1].size = sizeof(outopen);
 	req->out.args[1].value = &outopen;
···
 		return PTR_ERR(forget_req);
 	}
 
+	memset(&outarg, 0, sizeof(outarg));
 	req->in.h.nodeid = get_node_id(dir);
 	req->out.numargs = 1;
-	req->out.args[0].size = sizeof(outarg);
+	if (fc->minor < 9)
+		req->out.args[0].size = FUSE_COMPAT_ENTRY_OUT_SIZE;
+	else
+		req->out.args[0].size = sizeof(outarg);
 	req->out.args[0].value = &outarg;
 	request_send(fc, req);
 	err = req->out.h.error;
···
 	spin_unlock(&fc->lock);
 
 	memset(&inarg, 0, sizeof(inarg));
+	memset(&outarg, 0, sizeof(outarg));
 	/* Directories have separate file-handle space */
 	if (file && S_ISREG(inode->i_mode)) {
 		struct fuse_file *ff = file->private_data;
···
 	req->in.args[0].size = sizeof(inarg);
 	req->in.args[0].value = &inarg;
 	req->out.numargs = 1;
-	req->out.args[0].size = sizeof(outarg);
+	if (fc->minor < 9)
+		req->out.args[0].size = FUSE_COMPAT_ATTR_OUT_SIZE;
+	else
+		req->out.args[0].size = sizeof(outarg);
 	req->out.args[0].value = &outarg;
 	request_send(fc, req);
 	err = req->out.h.error;
···
 		return PTR_ERR(req);
 
 	memset(&inarg, 0, sizeof(inarg));
+	memset(&outarg, 0, sizeof(outarg));
 	iattr_to_fattr(attr, &inarg);
 	if (file) {
 		struct fuse_file *ff = file->private_data;
···
 	req->in.args[0].size = sizeof(inarg);
 	req->in.args[0].value = &inarg;
 	req->out.numargs = 1;
-	req->out.args[0].size = sizeof(outarg);
+	if (fc->minor < 9)
+		req->out.args[0].size = FUSE_COMPAT_ATTR_OUT_SIZE;
+	else
+		req->out.args[0].size = sizeof(outarg);
 	req->out.args[0].value = &outarg;
 	request_send(fc, req);
 	err = req->out.h.error;

fs/fuse/inode.c

···
 	inode->i_ctime.tv_sec   = attr->ctime;
 	inode->i_ctime.tv_nsec  = attr->ctimensec;
 
+	if (attr->blksize != 0)
+		inode->i_blkbits = ilog2(attr->blksize);
+	else
+		inode->i_blkbits = inode->i_sb->s_blocksize_bits;
+
 	/*
 	 * Don't set the sticky bit in i_mode, unless we want the VFS
 	 * to check permissions.  This prevents failures due to the

include/linux/fuse.h

···
  *  - new fuse_getattr_in input argument of GETATTR
  *  - add lk_flags in fuse_lk_in
  *  - add lock_owner field to fuse_setattr_in, fuse_read_in and fuse_write_in
+ *  - add blksize field to fuse_attr
  */
 
 #include <asm/types.h>
···
 	__u32	uid;
 	__u32	gid;
 	__u32	rdev;
+	__u32	blksize;
+	__u32	padding;
 };
 
 struct fuse_kstatfs {
···
 /* The read buffer is required to be at least 8k, but may be much larger */
 #define FUSE_MIN_READ_BUFFER 8192
 
+#define FUSE_COMPAT_ENTRY_OUT_SIZE 120
+
 struct fuse_entry_out {
 	__u64	nodeid;		/* Inode ID */
 	__u64	generation;	/* Inode generation: nodeid:gen must
···
 	__u32	dummy;
 	__u64	fh;
 };
+
+#define FUSE_COMPAT_ATTR_OUT_SIZE 96
 
 struct fuse_attr_out {
 	__u64	attr_valid;	/* Cache timeout for the attributes */