minix/lib/libsffs/inode.h
David van Moolenbroek ef7b484e5c Create SFFS library out of HGFS
This Shared Folders File System library (libsffs) now contains all the
file system logic originally in HGFS. The actual HGFS server code is
now a stub that passes on all the work to libsffs. The libhgfs library
is changed accordingly.
2012-04-09 18:08:26 +02:00

88 lines
4.3 KiB
C

#ifndef _SFFS_INODE_H
#define _SFFS_INODE_H
/* We cannot use inode number 0, so to be able to use bitmasks to combine
* inode and generation numbers, we have to use one fewer than the maximum of
* inodes possible by using NUM_INODE_BITS bits.
*/
#define NUM_INODES ((1 << NUM_INODE_BITS) - 1)
/* The main portion of the inode array forms a fully linked tree, providing a
* cached partial view of what the server believes is on the host system. Each
* inode contains only a pointer to its parent and its path component name, so
* a path for an inode is constructed by walking up to the root. Inodes that
* are in use as directory for a child node must not be recycled; in this case,
* the i_child list is not empty. Naturally, inodes for which VFS holds a
* reference must also not be recycled; the i_ref count takes care of that.
*
* Multiple hard links to a single file do not exist; that is why an inode is
* also a directory entry (when in IN USE or CACHED state). Notifications about
* modifications on the host system are not part of the protocol, so sometimes
* the server may discover that some files do not exist anymore. In that case,
* they are marked as DELETED in the inode table. Such files may still be used
* because of open file handles, but cannot be referenced by path anymore. The
* underlying protocol may not support truncation of open files anyway. Since
* we currently cannot guarantee that a file is actually opened before it is
* deleted (as this would consistute opening every file being looked up), we
* effectively do not properly support open deleted files at all anyway.
*
* An inode is REFERENCED iff it has a reference count > 0 *or* has children.
* An inode is LINKED IN iff it has a parent.
*
* An inode is IN USE iff it is REFERENCED and LINKED IN.
* An inode is CACHED iff it is NOT REFERENCED and LINKED IN.
* An inode is DELETED iff it is REFERENCED and NOT LINKED IN.
* An inode is FREE iff it is NOT REFERENCED and NOT LINKED IN.
*
* An inode may have an open file handle if it is IN USE or DELETED.
* An inode may have children if it is IN USE (and is a directory).
* An inode is in the names hashtable iff it is IN USE or CACHED.
* An inode is on the free list iff it is CACHED or FREE.
*
* - An IN USE inode becomes DELETED when it is either deleted explicitly, or
* when it has been determined to have become unreachable by path name on the
* host system (the verify_* functions take care of this).
* - An IN USE inode may become CACHED when there are no VFS references to it
* anymore (i_ref == 0), and it is not a directory with children.
* - A DELETED inode cannot have children, but may become FREE when there are
* also no VFS references to it anymore.
* - A CACHED inode may become IN USE when either i_ref or i_link is increased
* from zero. Practically, it will always be i_ref that gets increased, since
* i_link cannot be increased by VFS without having a reference to the inode.
* - A CACHED or FREE inode may be reused for other purposes at any time.
*/
struct inode {
struct inode *i_parent; /* parent inode pointer */
LIST_HEAD(child_head, inode) i_child; /* child inode anchor */
LIST_ENTRY(inode) i_next; /* sibling inode chain entry */
LIST_ENTRY(inode) i_hash; /* hashtable chain entry */
unsigned short i_num; /* inode number for quick reference */
unsigned short i_gen; /* inode generation number */
unsigned short i_ref; /* VFS reference count */
unsigned short i_flags; /* any combination of I_* flags */
union {
TAILQ_ENTRY(inode) i_free; /* free list chain entry */
sffs_file_t i_file; /* handle to open file */
sffs_dir_t i_dir; /* handle to open directory */
};
char i_name[NAME_MAX+1]; /* entry name in parent directory */
};
#define I_DIR 0x01 /* this inode represents a directory */
#define I_HANDLE 0x02 /* this inode has an open handle */
/* warning: the following line is not a proper macro */
#define INODE_NR(i) (((i)->i_gen << NUM_INODE_BITS) | (i)->i_num)
#define INODE_INDEX(n) (((n) & ((1 << NUM_INODE_BITS) - 1)) - 1)
#define INODE_GEN(n) (((n) >> NUM_INODE_BITS) & 0xffff)
#define ROOT_INODE_NR 1
#define IS_DIR(i) ((i)->i_flags & I_DIR)
#define IS_ROOT(i) ((i)->i_num == ROOT_INODE_NR)
#define HAS_CHILDREN(i) (!LIST_EMPTY(&(i)->i_child))
#define MODE_TO_DIRFLAG(m) (S_ISDIR(m) ? I_DIR : 0)
#endif /* _SFFS_INODE_H */