-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