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