Initial Spring 2016 commit.
This commit is contained in:
Geoffrey Challen
239
kern/fs/sfs/sfs_dir.c
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239
kern/fs/sfs/sfs_dir.c
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/*
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* Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009, 2014
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* The President and Fellows of Harvard College.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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/*
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* SFS filesystem
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*
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* Directory I/O
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*/
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#include <types.h>
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#include <kern/errno.h>
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#include <lib.h>
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#include <vfs.h>
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#include <sfs.h>
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#include "sfsprivate.h"
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/*
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* Read the directory entry out of slot SLOT of a directory vnode.
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* The "slot" is the index of the directory entry, starting at 0.
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*/
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static
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int
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sfs_readdir(struct sfs_vnode *sv, int slot, struct sfs_direntry *sd)
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{
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off_t actualpos;
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/* Compute the actual position in the directory to read. */
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actualpos = slot * sizeof(struct sfs_direntry);
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return sfs_metaio(sv, actualpos, sd, sizeof(*sd), UIO_READ);
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}
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/*
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* Write (overwrite) the directory entry in slot SLOT of a directory
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* vnode.
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*/
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static
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int
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sfs_writedir(struct sfs_vnode *sv, int slot, struct sfs_direntry *sd)
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{
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off_t actualpos;
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/* Compute the actual position in the directory. */
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KASSERT(slot>=0);
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actualpos = slot * sizeof(struct sfs_direntry);
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return sfs_metaio(sv, actualpos, sd, sizeof(*sd), UIO_WRITE);
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}
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/*
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* Compute the number of entries in a directory.
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* This actually computes the number of existing slots, and does not
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* account for empty slots.
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*/
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static
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int
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sfs_dir_nentries(struct sfs_vnode *sv)
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{
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struct sfs_fs *sfs = sv->sv_absvn.vn_fs->fs_data;
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off_t size;
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KASSERT(sv->sv_i.sfi_type == SFS_TYPE_DIR);
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size = sv->sv_i.sfi_size;
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if (size % sizeof(struct sfs_direntry) != 0) {
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panic("sfs: %s: directory %u: Invalid size %llu\n",
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sfs->sfs_sb.sb_volname, sv->sv_ino, size);
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}
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return size / sizeof(struct sfs_direntry);
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}
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/*
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* Search a directory for a particular filename in a directory, and
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* return its inode number, its slot, and/or the slot number of an
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* empty directory slot if one is found.
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*/
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int
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sfs_dir_findname(struct sfs_vnode *sv, const char *name,
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uint32_t *ino, int *slot, int *emptyslot)
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{
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struct sfs_direntry tsd;
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int found, nentries, i, result;
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nentries = sfs_dir_nentries(sv);
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/* For each slot... */
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found = 0;
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for (i=0; i<nentries; i++) {
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/* Read the entry from that slot */
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result = sfs_readdir(sv, i, &tsd);
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if (result) {
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return result;
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}
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if (tsd.sfd_ino == SFS_NOINO) {
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/* Free slot - report it back if one was requested */
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if (emptyslot != NULL) {
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*emptyslot = i;
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}
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}
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else {
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/* Ensure null termination, just in case */
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tsd.sfd_name[sizeof(tsd.sfd_name)-1] = 0;
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if (!strcmp(tsd.sfd_name, name)) {
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/* Each name may legally appear only once... */
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KASSERT(found==0);
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found = 1;
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if (slot != NULL) {
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*slot = i;
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}
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if (ino != NULL) {
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*ino = tsd.sfd_ino;
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}
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}
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}
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}
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return found ? 0 : ENOENT;
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}
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/*
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* Create a link in a directory to the specified inode by number, with
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* the specified name, and optionally hand back the slot.
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*/
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int
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sfs_dir_link(struct sfs_vnode *sv, const char *name, uint32_t ino, int *slot)
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{
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int emptyslot = -1;
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int result;
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struct sfs_direntry sd;
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/* Look up the name. We want to make sure it *doesn't* exist. */
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result = sfs_dir_findname(sv, name, NULL, NULL, &emptyslot);
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if (result!=0 && result!=ENOENT) {
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return result;
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}
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if (result==0) {
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return EEXIST;
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}
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if (strlen(name)+1 > sizeof(sd.sfd_name)) {
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return ENAMETOOLONG;
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}
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/* If we didn't get an empty slot, add the entry at the end. */
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if (emptyslot < 0) {
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emptyslot = sfs_dir_nentries(sv);
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}
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/* Set up the entry. */
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bzero(&sd, sizeof(sd));
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sd.sfd_ino = ino;
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strcpy(sd.sfd_name, name);
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/* Hand back the slot, if so requested. */
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if (slot) {
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*slot = emptyslot;
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}
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/* Write the entry. */
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return sfs_writedir(sv, emptyslot, &sd);
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}
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/*
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* Unlink a name in a directory, by slot number.
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*/
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int
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sfs_dir_unlink(struct sfs_vnode *sv, int slot)
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{
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struct sfs_direntry sd;
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/* Initialize a suitable directory entry... */
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bzero(&sd, sizeof(sd));
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sd.sfd_ino = SFS_NOINO;
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/* ... and write it */
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return sfs_writedir(sv, slot, &sd);
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}
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/*
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* Look for a name in a directory and hand back a vnode for the
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* file, if there is one.
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*/
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int
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sfs_lookonce(struct sfs_vnode *sv, const char *name,
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struct sfs_vnode **ret,
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int *slot)
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{
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struct sfs_fs *sfs = sv->sv_absvn.vn_fs->fs_data;
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uint32_t ino;
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int result;
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result = sfs_dir_findname(sv, name, &ino, slot, NULL);
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if (result) {
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return result;
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}
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result = sfs_loadvnode(sfs, ino, SFS_TYPE_INVAL, ret);
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if (result) {
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return result;
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}
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if ((*ret)->sv_i.sfi_linkcount == 0) {
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panic("sfs: %s: name %s (inode %u) in dir %u has "
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"linkcount 0\n", sfs->sfs_sb.sb_volname,
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name, (*ret)->sv_ino, sv->sv_ino);
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}
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return 0;
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}
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