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#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 */
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