1 #ifndef _SFFS_INODE_H 2 #define _SFFS_INODE_H 3 4 /* We cannot use inode number 0, so to be able to use bitmasks to combine 5 * inode and generation numbers, we have to use one fewer than the maximum of 6 * inodes possible by using NUM_INODE_BITS bits. 7 */ 8 #define NUM_INODES ((1 << NUM_INODE_BITS) - 1) 9 10 /* The main portion of the inode array forms a fully linked tree, providing a 11 * cached partial view of what the server believes is on the host system. Each 12 * inode contains only a pointer to its parent and its path component name, so 13 * a path for an inode is constructed by walking up to the root. Inodes that 14 * are in use as directory for a child node must not be recycled; in this case, 15 * the i_child list is not empty. Naturally, inodes for which VFS holds a 16 * reference must also not be recycled; the i_ref count takes care of that. 17 * 18 * Multiple hard links to a single file do not exist; that is why an inode is 19 * also a directory entry (when in IN USE or CACHED state). Notifications about 20 * modifications on the host system are not part of the protocol, so sometimes 21 * the server may discover that some files do not exist anymore. In that case, 22 * they are marked as DELETED in the inode table. Such files may still be used 23 * because of open file handles, but cannot be referenced by path anymore. The 24 * underlying protocol may not support truncation of open files anyway. Since 25 * we currently cannot guarantee that a file is actually opened before it is 26 * deleted (as this would consistute opening every file being looked up), we 27 * effectively do not properly support open deleted files at all anyway. 28 * 29 * An inode is REFERENCED iff it has a reference count > 0 *or* has children. 30 * An inode is LINKED IN iff it has a parent. 31 * 32 * An inode is IN USE iff it is REFERENCED and LINKED IN. 33 * An inode is CACHED iff it is NOT REFERENCED and LINKED IN. 34 * An inode is DELETED iff it is REFERENCED and NOT LINKED IN. 35 * An inode is FREE iff it is NOT REFERENCED and NOT LINKED IN. 36 * 37 * An inode may have an open file handle if it is IN USE or DELETED. 38 * An inode may have children if it is IN USE (and is a directory). 39 * An inode is in the names hashtable iff it is IN USE or CACHED. 40 * An inode is on the free list iff it is CACHED or FREE. 41 * 42 * - An IN USE inode becomes DELETED when it is either deleted explicitly, or 43 * when it has been determined to have become unreachable by path name on the 44 * host system (the verify_* functions take care of this). 45 * - An IN USE inode may become CACHED when there are no VFS references to it 46 * anymore (i_ref == 0), and it is not a directory with children. 47 * - A DELETED inode cannot have children, but may become FREE when there are 48 * also no VFS references to it anymore. 49 * - A CACHED inode may become IN USE when either i_ref or i_link is increased 50 * from zero. Practically, it will always be i_ref that gets increased, since 51 * i_link cannot be increased by VFS without having a reference to the inode. 52 * - A CACHED or FREE inode may be reused for other purposes at any time. 53 */ 54 55 struct inode { 56 struct inode *i_parent; /* parent inode pointer */ 57 LIST_HEAD(child_head, inode) i_child; /* child inode anchor */ 58 LIST_ENTRY(inode) i_next; /* sibling inode chain entry */ 59 LIST_ENTRY(inode) i_hash; /* hashtable chain entry */ 60 unsigned short i_num; /* inode number for quick reference */ 61 unsigned short i_gen; /* inode generation number */ 62 unsigned short i_ref; /* VFS reference count */ 63 unsigned short i_flags; /* any combination of I_* flags */ 64 union { 65 TAILQ_ENTRY(inode) i_free; /* free list chain entry */ 66 sffs_file_t i_file; /* handle to open file */ 67 sffs_dir_t i_dir; /* handle to open directory */ 68 }; 69 char i_name[NAME_MAX+1]; /* entry name in parent directory */ 70 }; 71 72 #define I_DIR 0x01 /* this inode represents a directory */ 73 #define I_HANDLE 0x02 /* this inode has an open handle */ 74 75 /* warning: the following line is not a proper macro */ 76 #define INODE_NR(i) (((i)->i_gen << NUM_INODE_BITS) | (i)->i_num) 77 #define INODE_INDEX(n) (((n) & ((1 << NUM_INODE_BITS) - 1)) - 1) 78 #define INODE_GEN(n) (((n) >> NUM_INODE_BITS) & 0xffff) 79 80 #define ROOT_INODE_NR 1 81 82 #define IS_DIR(i) ((i)->i_flags & I_DIR) 83 #define IS_ROOT(i) ((i)->i_num == ROOT_INODE_NR) 84 #define HAS_CHILDREN(i) (!LIST_EMPTY(&(i)->i_child)) 85 86 #define MODE_TO_DIRFLAG(m) (S_ISDIR(m) ? I_DIR : 0) 87 88 #endif /* _SFFS_INODE_H */ 89