+Considerations for an API between OBD's and OBDFS
+
+
+OBDFS
+
+Methods needed:
+
+struct super_operations {
+ void (*read_inode) (struct inode *);
+ void (*write_inode) (struct inode *);
+ void (*put_inode) (struct inode *);
+ void (*delete_inode) (struct inode *);
+ int (*notify_change) (struct dentry *, struct iattr *);
+ void (*put_super) (struct super_block *);
+ void (*write_super) (struct super_block *);
+ int (*statfs) (struct super_block *, struct statfs *, int);
+* int (*remount_fs) (struct super_block *, int *, char *);
+ void (*clear_inode) (struct inode *);
+* void (*umount_begin) (struct super_block *);
+};
+
+
+read_inode:
+
+Called from function iget(ino, dev) - through get_new_inode.
+Typically called only when a VFS inode is instantiated by FS, i.e.
+upon lookup, create, mkdir, or upon mounting for the / inode.
+
+ - executed for new inodes and for existing inodes
+ - for new inodes, avoid traffic to disk
+
+E.g:
+
+lookup("name in dir-inode")
+{
+ get data from dir-inode;
+ find ino of "name" in this data;
+ iget(sb(dev), ino);
+ ---> calls read_inode
+ ----> obd_getattr(obj-no = ino)
+}
+
+create("name in dir-inode")
+{
+ get ino for name from pre-alloced obj-no's
+ ---> may call obd_prealloc_ids(hint)
+
+ iget(sb(dev), ino)
+ ---> call read_inode
+ ---> do not contact OBD, fill in from FS
+
+ change data from dir-inode, to contain ("name, ino");
+}
+
+mkdir("name in dir-inode")
+{
+ as above
+}
+
+read_super(dev, data)
+{
+ struct obdfs_sb *sb = ... ;
+ obd_connect(dev, &sb->obdfs_conn_info);
+
+ iget(sb, sb->obdfs_conn_info->conn_ino);
+
+
+}
+
+We currently have:
+
+struct obd_conn_info {
+ unsigned int conn_id;
+ unsigned long conn_ino;
+ unsigned long conn_blocksize;
+ unsigned char conn_blocksize_bits;
+};
+
+read_inode(inode)
+{
+ struct iattr attr;
+
+
+ if ( inode in inode_attr cache ) {
+ get_attr_from_cache(inode, &attr);
+ } else {
+ obd_getattr(conn_id, inode->i_ino, &attr);
+ }
+
+ inode_setattr(inode, &attr);
+}
+
+Write_inode is called from the bdflush (sync_dev) routines, through
+write_inode, sync_inode, sync_list, sync_inodes etc:
+
+void sync_dev(kdev_t dev)
+{
+ sync_buffers(dev, 0);
+ sync_supers(dev);
+ sync_inodes(dev);
+ sync_buffers(dev, 0);
+ DQUOT_SYNC(dev);
+ /*
+ * FIXME(eric) we need to sync the physical devices here.
+ * This is because some (scsi) controllers have huge amounts of
+ * cache onboard (hundreds of Mb), and we need to instruct
+ * them to commit all of the dirty memory to disk, and we should
+ * not return until this has happened.
+ *
+ * This would need to get implemented by going through the assorted
+ * layers so that each block major number can be synced, and this
+ * would call down into the upper and mid-layer scsi.
+ */
+}
+
+This sync_inodes function is responsible (for "block" disk file
+systems) for copying the modified inode metadata into the buffer
+cache. The sync_buffers call which follows sync_inodes is responsible
+for writing back this meta data. For OBD's this is different.
+
+I expect the following routine to be there:
+
+sync_inode_pages(dev,0);
+sync_supers(dev);
+sync_inode_metadata(dev);
+
+
+The statfs function should return simple summary information available
+on the disk: %free, total space, etc. May require a new obd_command.
+
+Similarly write_super would instruct the disk to commit any pending
+data. This is called from do_unmount just before put_super (the
+latter breaks down the vm super block structure).
+
+Write_super should:
+- undo pre-allocated inode numbers
+
+The disk itself also needs a cleanup function.
+
+struct file_operations {
+ loff_t (*llseek) (struct file *, loff_t, int);
+ ssize_t (*read) (struct file *, char *, size_t, loff_t *);
+ ssize_t (*write) (struct file *, const char *, size_t, loff_t *);
+ int (*readdir) (struct file *, void *, filldir_t);
+ unsigned int (*poll) (struct file *, struct poll_table_struct *);
+ int (*ioctl) (struct inode *, struct file *, unsigned int, unsigned long);
+ int (*mmap) (struct file *, struct vm_area_struct *);
+ int (*open) (struct inode *, struct file *);
+ int (*flush) (struct file *);
+ int (*release) (struct inode *, struct file *);
+ int (*fsync) (struct file *, struct dentry *);
+ int (*fasync) (int, struct file *, int);
+ int (*check_media_change) (kdev_t dev);
+ int (*revalidate) (kdev_t dev);
+ int (*lock) (struct file *, int, struct file_lock *);
+};
+
+
+struct inode_operations {
+ struct file_operations * default_file_ops;
+ int (*create) (struct inode *,struct dentry *,int);
+ struct dentry * (*lookup) (struct inode *,struct dentry *);
+ int (*link) (struct dentry *,struct inode *,struct dentry *);
+ int (*unlink) (struct inode *,struct dentry *);
+ int (*symlink) (struct inode *,struct dentry *,const char *);
+ int (*mkdir) (struct inode *,struct dentry *,int);
+ int (*rmdir) (struct inode *,struct dentry *);
+ int (*mknod) (struct inode *,struct dentry *,int,int);
+ int (*rename) (struct inode *, struct dentry *,
+ struct inode *, struct dentry *);
+ int (*readlink) (struct dentry *, char *,int);
+ struct dentry * (*follow_link) (struct dentry *, struct dentry *, unsigned int);
+ /*
+ * the order of these functions within the VFS template has been
+ * changed because SMP locking has changed: from now on all get_block,
+ * readpage, writepage and flushpage functions are supposed to do
+ * whatever locking they need to get proper SMP operation - for
+ * now in most cases this means a lock/unlock_kernel at entry/exit.
+ * [The new order is also slightly more logical :)]
+ */
+ /*
+ * Generic block allocator exported by the lowlevel fs. All metadata
+ * details are handled by the lowlevel fs, all 'logical data content'
+ * details are handled by the highlevel block layer.
+ */
+ int (*get_block) (struct inode *, long, struct buffer_head *, int);
+
+ int (*readpage) (struct file *, struct page *);
+ int (*writepage) (struct file *, struct page *);
+ int (*flushpage) (struct inode *, struct page *, unsigned long);
+
+ void (*truncate) (struct inode *);
+ int (*permission) (struct inode *, int);
+ int (*smap) (struct inode *,int);
+ int (*revalidate) (struct dentry *);
+};
+
+
git://git.whamcloud.com / fs / lustre-release.git / commitdiff