Changes pde_t* -> pgdir_t

[akaros.git] / kern / src / kfs.c

/* Copyright (c) 2009, 2010 The Regents of the University of California
 * Barret Rhoden <brho@cs.berkeley.edu>
 * See LICENSE for details.
 *
 * Implementation of the KFS file system.  It is a RAM based, read-only FS
 * consisting of files that are added to the kernel binary image.  Might turn
 * this into a read/write FS with directories someday. */

#ifdef __SHARC__
#pragma nosharc
#endif

#ifdef __DEPUTY__
#pragma nodeputy
#endif

#include <vfs.h>
#include <kfs.h>
#include <slab.h>
#include <kmalloc.h>
#include <string.h>
#include <stdio.h>
#include <assert.h>
#include <error.h>
#include <cpio.h>
#include <pmap.h>
#include <smp.h>

#define KFS_MAX_FILE_SIZE 1024*1024*128
#define KFS_MAGIC 0xdead0001

/* VFS required Functions */
/* These structs are declared again and initialized farther down */
struct page_map_operations kfs_pm_op;
struct super_operations kfs_s_op;
struct inode_operations kfs_i_op;
struct dentry_operations kfs_d_op;
struct file_operations kfs_f_op_file;
struct file_operations kfs_f_op_dir;
struct file_operations kfs_f_op_sym;

/* TODO: something more better.  Prob something like the vmem cache, for this,
 * pids, etc.  Good enough for now.  This also means we can only have one
 * KFS instance, and we also aren't synchronizing access. */
static unsigned long kfs_get_free_ino(void)
{
        static unsigned long last_ino = 1;       /* 1 is reserved for the root */
        last_ino++;
        if (!last_ino)
                panic("Out of inos in KFS!");
        return last_ino;
}

/* Slabs for KFS specific info chunks */
struct kmem_cache *kfs_i_kcache;

static void kfs_init(void)
{
        kfs_i_kcache = kmem_cache_create("kfs_ino_info", sizeof(struct kfs_i_info),
                                         __alignof__(struct kfs_i_info), 0, 0, 0);
}

/* Creates the SB (normally would read in from disc and create).  Passes it's
 * ref out to whoever consumes this.  Returns 0 on failure.
 * TODO: consider pulling out more of the FS-independent stuff, if possible.
 * There are only two things, but the pain in the ass is that you'd need to read
 * the disc to get that first inode, and it's a FS-specific thing. */
struct super_block *kfs_get_sb(struct fs_type *fs, int flags,
                               char *dev_name, struct vfsmount *vmnt)
{
        /* Ought to check that dev_name has our FS on it.  in this case, it's
         * irrelevant. */
        //if (something_bad)
        //      return 0;
        static bool ran_once = FALSE;
        if (!ran_once) {
                ran_once = TRUE;
                kfs_init();
        }

        /* Build and init the SB.  No need to read off disc. */
        struct super_block *sb = get_sb();
        sb->s_dev = 0;
        sb->s_blocksize = 1;
        sb->s_maxbytes = KFS_MAX_FILE_SIZE;
        sb->s_type = &kfs_fs_type;
        sb->s_op = &kfs_s_op;
        sb->s_flags = flags;
        sb->s_magic = KFS_MAGIC;
        sb->s_mount = vmnt;
        sb->s_syncing = FALSE;
        sb->s_bdev = 0;
        strlcpy(sb->s_name, "KFS", 32);
        /* store the location of the CPIO archive.  make this more generic later. */
        extern uint8_t _binary_obj_kern_initramfs_cpio_size[];
        extern uint8_t _binary_obj_kern_initramfs_cpio_start[];
        sb->s_fs_info = (void*)_binary_obj_kern_initramfs_cpio_start;

        /* Final stages of initializing the sb, mostly FS-independent */
        /* 1 is the KFS root ino (inode number) */
        init_sb(sb, vmnt, &kfs_d_op, 1, 0);
        /* Parses the CPIO entries and builds the in-memory KFS tree. */
        parse_cpio_entries(sb, sb->s_fs_info);
        printk("KFS superblock loaded\n");
        return sb;
}

void kfs_kill_sb(struct super_block *sb)
{
        panic("Killing KFS is not supported!");
}

/* Every FS must have a static FS Type, with which the VFS code can bootstrap */
struct fs_type kfs_fs_type = {"KFS", 0, kfs_get_sb, kfs_kill_sb, {0, 0},
               TAILQ_HEAD_INITIALIZER(kfs_fs_type.fs_supers)};

/* Page Map Operations */

/* Fills page with its contents from its backing store file.  Note that we do
 * the zero padding here, instead of higher in the VFS.  Might change in the
 * future. */
int kfs_readpage(struct page_map *pm, struct page *page)
{
        size_t pg_idx_byte = page->pg_index * PGSIZE;
        struct kfs_i_info *k_i_info = (struct kfs_i_info*)
                                      pm->pm_host->i_fs_info;
        uintptr_t begin = (size_t)k_i_info->filestart + pg_idx_byte;
        /* If we're beyond the initial start point, we just need a zero page.  This
         * is for a hole or for extending a file (even though it won't be saved).
         * Otherwise, we want the data from KFS, being careful to not copy from
         * beyond the original EOF (and zero padding anything extra). */
        if (pg_idx_byte >= k_i_info->init_size) {
                memset(page2kva(page), 0, PGSIZE);
        } else {
                size_t copy_amt = MIN(PGSIZE, k_i_info->init_size - pg_idx_byte);
                memcpy(page2kva(page), (void*)begin, copy_amt);
                memset(page2kva(page) + copy_amt, 0, PGSIZE - copy_amt);
        }
        struct buffer_head *bh = kmem_cache_alloc(bh_kcache, 0);
        if (!bh)
                return -1;                      /* untested, un-thought-through */
        atomic_or(&page->pg_flags, PG_BUFFER);
        /* KFS does a 1:1 BH to page mapping */
        bh->bh_page = page;                                                             /* weak ref */
        bh->bh_buffer = page2kva(page);
        bh->bh_flags = 0;                                                               /* whatever... */
        bh->bh_next = 0;                                                                /* only one BH needed */
        bh->bh_bdev = pm->pm_host->i_sb->s_bdev;                /* uncounted */
        bh->bh_sector = page->pg_index;
        bh->bh_nr_sector = 1;                                                   /* sector size = PGSIZE */
        page->pg_private = bh;
        /* This is supposed to be done in the IO system when the operation is
         * complete.  Since we aren't doing a real IO request, and it is already
         * done, we can do it here. */
        atomic_or(&page->pg_flags, PG_UPTODATE);
        return 0;
}

int kfs_writepage(struct page_map *pm, struct page *page)
{
        warn_once("KFS writepage does not save file contents!\n");
        return -1;
}

/* Super Operations */

/* Creates and initializes a new inode.  FS specific, yet inode-generic fields
 * are filled in.  inode-specific fields are filled in in read_inode() based on
 * what's on the disk for a given i_no.  i_no and i_fop are set by the caller.
 *
 * Note that this means this inode can be for an inode that is already on disk,
 * or it can be used when creating.  The i_fop depends on the type of file
 * (file, directory, symlink, etc). */
struct inode *kfs_alloc_inode(struct super_block *sb)
{
        struct inode *inode = kmem_cache_alloc(inode_kcache, 0);
        memset(inode, 0, sizeof(struct inode));
        inode->i_op = &kfs_i_op;
        inode->i_pm.pm_op = &kfs_pm_op;
        inode->i_fs_info = kmem_cache_alloc(kfs_i_kcache, 0);
        TAILQ_INIT(&((struct kfs_i_info*)inode->i_fs_info)->children);
        ((struct kfs_i_info*)inode->i_fs_info)->filestart = 0;
        ((struct kfs_i_info*)inode->i_fs_info)->init_size = 0;
        return inode;
}

/* FS-specific clean up when an inode is dealloced.  this is just cleaning up
 * the in-memory version, and only the FS-specific parts.  whether or not the
 * inode is still on disc is irrelevant. */
void kfs_dealloc_inode(struct inode *inode)
{
        /* If we're a symlink, give up our storage for the symname */
        if (S_ISLNK(inode->i_mode))
                kfree(((struct kfs_i_info*)inode->i_fs_info)->filestart);
        kmem_cache_free(kfs_i_kcache, inode->i_fs_info);
}

/* reads the inode data on disk specified by inode->i_ino into the inode.
 * basically, it's a "make this inode the one for i_ino (i number)" */
void kfs_read_inode(struct inode *inode)
{
        /* need to do something to link this inode/file to the actual "blocks" on
         * "disk". */

        /* TODO: what does it mean to ask for an inode->i_ino that doesn't exist?
         *      possibly a bug, since these inos come from directories */
        if (inode->i_ino == 1) {
                inode->i_mode = S_IRWXU | S_IRWXG | S_IRWXO;
                SET_FTYPE(inode->i_mode, __S_IFDIR);
                inode->i_fop = &kfs_f_op_dir;
                inode->i_nlink = 1;                             /* assuming only one hardlink */
                inode->i_uid = 0;
                inode->i_gid = 0;
                inode->i_size = 0;                              /* make sense for KFS? */
                inode->i_atime.tv_sec = 0;
                inode->i_atime.tv_nsec = 0;
                inode->i_mtime.tv_sec = 0;
                inode->i_mtime.tv_nsec = 0;
                inode->i_ctime.tv_sec = 0;
                inode->i_ctime.tv_nsec = 0;
                inode->i_blocks = 0;
                inode->i_flags = 0;
                inode->i_socket = FALSE;
        } else {
                panic("Not implemented");
        }
        /* TODO: unused: inode->i_hash add to hash (saves on disc reading) */
}

/* called when an inode in memory is modified (journalling FS's care) */
void kfs_dirty_inode(struct inode *inode)
{       // KFS doesn't care
}

/* write the inode to disk (specifically, to inode inode->i_ino), synchronously
 * if we're asked to wait */
void kfs_write_inode(struct inode *inode, bool wait)
{       // KFS doesn't care
}

/* called when an inode is decref'd, to do any FS specific work */
void kfs_put_inode(struct inode *inode)
{       // KFS doesn't care
}

/* called when an inode is about to be destroyed.  the generic version ought to
 * remove every reference to the inode from the VFS, and if the inode isn't in
 * any directory, calls delete_inode */
void kfs_drop_inode(struct inode *inode)
{ // TODO: should call a generic one instead.  or at least do something...
        // remove from lists
}

/* delete the inode from disk (all data) */
void kfs_delete_inode(struct inode *inode)
{
        // would remove from "disk" here
        /* TODO: give up our i_ino */
}

/* unmount and release the super block */
void kfs_put_super(struct super_block *sb)
{
        panic("Shazbot! KFS can't be unmounted yet!");
}

/* updates the on-disk SB with the in-memory SB */
void kfs_write_super(struct super_block *sb)
{       // KFS doesn't care
}

/* syncs FS metadata with the disc, synchronously if we're waiting.  this info
 * also includes anything pointed to by s_fs_info. */
int kfs_sync_fs(struct super_block *sb, bool wait)
{
        return 0;
}

/* remount the FS with the new flags */
int kfs_remount_fs(struct super_block *sb, int flags, char *data)
{
        warn("KFS will not remount.");
        return -1; // can't remount
}

/* interrupts a mount operation - used by NFS and friends */
void kfs_umount_begin(struct super_block *sb)
{
        panic("Cannot abort a KFS mount, and why would you?");
}

/* inode_operations */

/* Little helper, used for initializing new inodes for file-like objects (files,
 * symlinks, etc).  We pass the dentry, since we need to up it. */
static void kfs_init_inode(struct inode *dir, struct dentry *dentry)
{
        struct inode *inode = dentry->d_inode;
        kref_get(&dentry->d_kref, 1);   /* to pin the dentry in RAM, KFS-style... */
        inode->i_ino = kfs_get_free_ino();
        /* our parent dentry's inode tracks our dentry info.  We do this
         * since it's all in memory and we aren't using the dcache yet.
         * We're reusing the subdirs link, which is used by the VFS when
         * we're a directory.  But since we're a file, it's okay to reuse
         * it. */
        TAILQ_INSERT_TAIL(&((struct kfs_i_info*)dir->i_fs_info)->children,
                          dentry, d_subdirs_link);
}

/* Called when creating a new disk inode in dir associated with dentry.  We need
 * to fill out the i_ino, set the type, and do whatever else we need */
int kfs_create(struct inode *dir, struct dentry *dentry, int mode,
               struct nameidata *nd)
{
        struct inode *inode = dentry->d_inode;
        kfs_init_inode(dir, dentry);
        SET_FTYPE(inode->i_mode, __S_IFREG);
        inode->i_fop = &kfs_f_op_file;
        /* fs_info->filestart is set by the caller, or else when first written (for
         * new files.  it was set to 0 in alloc_inode(). */
        return 0;
}

/* Searches the directory for the filename in the dentry, filling in the dentry
 * with the FS specific info of this file.  If it succeeds, it will pass back
 * the *dentry you should use.  If this fails, it will return 0.  It will NOT
 * take your dentry ref (it used to).  It probably will not be the same dentry
 * you passed in.  This is ugly.
 *
 * Callers, make sure you alloc and fill out the name parts of the dentry, and
 * an initialized nameidata. TODO: not sure why we need an ND.  Don't use it in
 * a fs_lookup for now!
 *
 * Because of the way KFS currently works, if there is ever a dentry, it's
 * already in memory, along with its inode (all path's pinned).  So we just find
 * it and return it, freeing the one that came in. */
struct dentry *kfs_lookup(struct inode *dir, struct dentry *dentry,
                          struct nameidata *nd)
{
        struct kfs_i_info *k_i_info = (struct kfs_i_info*)dir->i_fs_info;
        struct dentry *dir_dent = TAILQ_FIRST(&dir->i_dentry);
        struct dentry *d_i;

        assert(dir_dent && dir_dent == TAILQ_LAST(&dir->i_dentry, dentry_tailq));
        /* had this fail when kern/kfs has a symlink go -> ../../../go, though
         * a symlink like lib2 -> lib work okay. */
        assert(S_ISDIR(dir->i_mode));
        assert(kref_refcnt(&dentry->d_kref) == 1);
        TAILQ_FOREACH(d_i, &dir_dent->d_subdirs, d_subdirs_link) {
                if (!strcmp(d_i->d_name.name, dentry->d_name.name)) {
                        /* since this dentry is already in memory (that's how KFS works), we
                         * just return the real one (with another refcnt) */
                        kref_get(&d_i->d_kref, 1);
                        return d_i;
                }
        }
        TAILQ_FOREACH(d_i, &k_i_info->children, d_subdirs_link) {
                if (!strcmp(d_i->d_name.name, dentry->d_name.name)) {
                        /* since this dentry is already in memory (that's how KFS works), we
                         * just return the real one (with another refcnt) */
                        kref_get(&d_i->d_kref, 1);
                        return d_i;
                }
        }
        printd("Not Found %s!!\n", dentry->d_name.name);
        return 0;
}

/* Hard link to old_dentry in directory dir with a name specified by new_dentry.
 * At the very least, set the new_dentry's FS-specific fields. */
int kfs_link(struct dentry *old_dentry, struct inode *dir,
             struct dentry *new_dentry)
{
        assert(new_dentry->d_op = &kfs_d_op);
        kref_get(&new_dentry->d_kref, 1);               /* pin the dentry, KFS-style */
        /* KFS-style directory-tracking-of-kids */
        TAILQ_INSERT_TAIL(&((struct kfs_i_info*)dir->i_fs_info)->children,
                          new_dentry, d_subdirs_link);
        return 0;
}

/* Removes the link from the dentry in the directory */
int kfs_unlink(struct inode *dir, struct dentry *dentry)
{
        /* Stop tracking our child */
        TAILQ_REMOVE(&((struct kfs_i_info*)dir->i_fs_info)->children, dentry,
                     d_subdirs_link);
        kref_put(&dentry->d_kref);                              /* unpin the dentry, KFS-style */
        return 0;
}

/* Creates a new inode for a symlink dir, linking to / containing the name
 * symname.  dentry is the controlling dentry of the inode. */
int kfs_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
{
        struct inode *inode = dentry->d_inode;
        struct kfs_i_info *k_i_info = (struct kfs_i_info*)inode->i_fs_info;
        size_t len = strlen(symname);
        char *string = kmalloc(len + 1, 0);

        kfs_init_inode(dir, dentry);
        SET_FTYPE(inode->i_mode, __S_IFLNK);
        inode->i_fop = &kfs_f_op_sym;
        strncpy(string, symname, len);
        string[len] = '\0';             /* symname should be \0d anyway, but just in case */
        k_i_info->filestart = string;   /* reusing this void* to hold the char* */
        return 0;
}

/* Called when creating a new inode for a directory associated with dentry in
 * dir with the given mode.  Note, we might (later) need to track subdirs within
 * the parent inode, like we do with regular files.  I'd rather not, so we'll
 * see if we need it. */
int kfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
{
        struct inode *inode = dentry->d_inode;
        kref_get(&dentry->d_kref, 1);   /* to pin the dentry in RAM, KFS-style... */
        inode->i_ino = kfs_get_free_ino();
        SET_FTYPE(inode->i_mode, __S_IFDIR);
        inode->i_fop = &kfs_f_op_dir;
        /* get ready to have our own kids */
        TAILQ_INIT(&((struct kfs_i_info*)inode->i_fs_info)->children);
        ((struct kfs_i_info*)inode->i_fs_info)->filestart = 0;
        return 0;
}

/* Removes from dir the directory 'dentry.'  KFS doesn't store anything in the
 * inode for which children it has.  It probably should, but since everything is
 * pinned, it just relies on the dentry connections. */
int kfs_rmdir(struct inode *dir, struct dentry *dentry)
{
        struct kfs_i_info *d_info = (struct kfs_i_info*)dentry->d_inode->i_fs_info;
        struct dentry *d_i;
        bool empty = TRUE;
        /* Check if we are empty.  If not, error out, need to check the sub-dirs as
         * well as the sub-"files" */
        TAILQ_FOREACH(d_i, &dentry->d_subdirs, d_subdirs_link) {
                empty = FALSE;
                break;
        }
        TAILQ_FOREACH(d_i, &d_info->children, d_subdirs_link) {
                empty = FALSE;
                break;
        }
        if (!empty)
                return -ENOTEMPTY;
        kref_put(&dentry->d_kref);                              /* unpin the dentry, KFS-style */
        printd("DENTRY %s REFCNT %d\n", dentry->d_name.name, kref_refcnt(&dentry->d_kref));
        return 0;
}

/* Used to make a generic file, based on the type and the major/minor numbers
 * (in rdev), with the given mode.  As with others, this creates a new disk
 * inode for the file */
int kfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t rdev)
{
        return -1;
}

/* Moves old_d from old_dir to new_d in new_dir.  TODO: super racy */
int kfs_rename(struct inode *old_dir, struct dentry *old_d,
               struct inode *new_dir, struct dentry *new_d)
{
        /* new_d is already gone, we just use it for its name.  kfs might not care
         * about the name.  it might just use whatever the dentry says. */
        struct kfs_i_info *old_info = (struct kfs_i_info*)old_dir->i_fs_info;
        struct kfs_i_info *new_info = (struct kfs_i_info*)new_dir->i_fs_info;
        printd("KFS rename: %s/%s -> %s/%s\n",
               TAILQ_FIRST(&old_dir->i_dentry)->d_name.name, old_d->d_name.name,
               TAILQ_FIRST(&new_dir->i_dentry)->d_name.name, new_d->d_name.name);
        /* we want to remove from the old and add to the new.  for non-directories,
         * we need to adjust parent's children lists (which reuses subdirs_link,
         * yikes!).  directories aren't actually tracked by KFS; it just hopes the
         * VFS's pinned dentry tree is enough (aka, "all paths pinned"). */
        if (!S_ISDIR(old_d->d_inode->i_mode)) {
                TAILQ_REMOVE(&old_info->children, old_d, d_subdirs_link);
                TAILQ_INSERT_TAIL(&new_info->children, old_d, d_subdirs_link);
        }
        return 0;
}

/* Returns the char* for the symname for the given dentry.  The VFS code that
 * calls this for real FS's might assume it's already read in, so if the char *
 * isn't already in memory, we'd need to read it in here.  Regarding the char*
 * storage, the char* only will last as long as the dentry and inode are in
 * memory. */
char *kfs_readlink(struct dentry *dentry)
{
        struct inode *inode = dentry->d_inode;
        struct kfs_i_info *k_i_info = (struct kfs_i_info*)inode->i_fs_info;
        if (!S_ISLNK(inode->i_mode))
                return 0;
        return k_i_info->filestart;
}

/* Modifies the size of the file of inode to whatever its i_size is set to */
void kfs_truncate(struct inode *inode)
{
        struct kfs_i_info *k_i_info = (struct kfs_i_info*)inode->i_fs_info;
        /* init_size tracks how much of the file KFS has.  everything else is 0s.
         * we only need to update it if we are dropping data.  as with other data
         * beyond init_size, KFS will not save it during a write page! */
        k_i_info->init_size = MIN(k_i_info->init_size, inode->i_size);
}

/* Checks whether the the access mode is allowed for the file belonging to the
 * inode.  Implies that the permissions are on the file, and not the hardlink */
int kfs_permission(struct inode *inode, int mode, struct nameidata *nd)
{
        return -1;
}


/* dentry_operations */
/* Determines if the dentry is still valid before using it to translate a path.
 * Network FS's need to deal with this. */
int kfs_d_revalidate(struct dentry *dir, struct nameidata *nd)
{ // default, nothing
        return -1;
}

/* Compares name1 and name2.  name1 should be a member of dir. */
int kfs_d_compare(struct dentry *dir, struct qstr *name1, struct qstr *name2)
{ // default, string comp (case sensitive)
        return -1;
}

/* Called when the last ref is deleted (refcnt == 0) */
int kfs_d_delete(struct dentry *dentry)
{ // default, nothin
        return -1;
}

/* Called when it's about to be slab-freed */
int kfs_d_release(struct dentry *dentry)
{
        return -1;
}

/* Called when the dentry loses it's inode (becomes "negative") */
void kfs_d_iput(struct dentry *dentry, struct inode *inode)
{ // default, call i_put to release the inode object
}


/* file_operations */

/* Updates the file pointer.  TODO: think about locking. */
int kfs_llseek(struct file *file, off64_t offset, off64_t *ret, int whence)
{
        off64_t temp_off = 0;
        switch (whence) {
                case SEEK_SET:
                        temp_off = offset;
                        break;
                case SEEK_CUR:
                        temp_off = file->f_pos + offset;
                        break;
                case SEEK_END:
                        temp_off = file->f_dentry->d_inode->i_size + offset;
                        break;
                default:
                        set_errno(EINVAL);
                        warn("Unknown 'whence' in llseek()!\n");
                        return -1;
        }
        file->f_pos = temp_off;
        *ret = temp_off;
        return 0;
}

/* Fills in the next directory entry (dirent), starting with d_off.  KFS treats
 * the size of each dirent as 1 byte, which we can get away with since the d_off
 * is a way of communicating with future calls to readdir (FS-specific).
 *
 * Like with read and write, there will be issues with userspace and the *dirent
 * buf.  TODO: we don't really do anything with userspace concerns here, in part
 * because memcpy_to doesn't work well.  When we fix how we want to handle the
 * userbuffers, we can write this accordingly. (UMEM)  */
int kfs_readdir(struct file *dir, struct dirent *dirent)
{
        int count = 2;  /* total num dirents, gets incremented in check_entry() */
        int desired_file = dirent->d_off;
        bool found = FALSE;
        struct dentry *subent;
        struct dentry *dir_d = dir->f_dentry;
        struct kfs_i_info *k_i_info = (struct kfs_i_info*)dir_d->d_inode->i_fs_info;

        /* how we check inside the for loops below.  moderately ghetto. */
        void check_entry(void)
        {
                if (count++ == desired_file) {
                        dirent->d_ino = subent->d_inode->i_ino;
                        dirent->d_off = count;
                        dirent->d_reclen = subent->d_name.len;
                        /* d_name.name is null terminated, the byte after d_name.len */
                        assert(subent->d_name.len <= MAX_FILENAME_SZ);
                        strncpy(dirent->d_name, subent->d_name.name, subent->d_name.len +1);
                        found = TRUE;
                }
        }

        /* Handle . and .. (first two dirents) */
        if (desired_file == 0) {
                dirent->d_ino = dir_d->d_inode->i_ino;
                dirent->d_off = 1;
                dirent->d_reclen = 1;
                strncpy(dirent->d_name, ".", 2);        /* the extra is for the null term */
                found = TRUE;
        } else if (desired_file == 1) {
                dirent->d_ino = dir_d->d_parent->d_inode->i_ino;
                dirent->d_off = 2;
                dirent->d_reclen = 2;
                strncpy(dirent->d_name, "..", 3);       /* the extra is for the null term */
                found = TRUE;
        }
        /* need to check the sub-dirs as well as the sub-"files".  The main
         * ghetto-ness with this is that we check even though we have our result,
         * simply to figure out how big our directory is.  It's just not worth
         * changing at this point. */
        TAILQ_FOREACH(subent, &dir_d->d_subdirs, d_subdirs_link)
                check_entry();
        TAILQ_FOREACH(subent, &k_i_info->children, d_subdirs_link)
                check_entry();
        if (!found)
                return -ENOENT;
        if (count - 1 == desired_file)          /* found the last dir in the list */
                return 0;
        return 1;                                                       /* normal success for readdir */
}

/* This is called when a VMR is mapping a particular file.  The FS needs to do
 * whatever it needs so that faults can be handled by read_page(), and handle all
 * of the cases of MAP_SHARED, MAP_PRIVATE, whatever.  It also needs to ensure
 * the file is not being mmaped in a way that conflicts with the manner in which
 * the file was opened or the file type. */
int kfs_mmap(struct file *file, struct vm_region *vmr)
{
        if (S_ISREG(file->f_dentry->d_inode->i_mode))
                return 0;
        return -1;
}

/* Called by the VFS while opening the file, which corresponds to inode,  for
 * the FS to do whatever it needs. */
int kfs_open(struct inode *inode, struct file *file)
{
        return 0;
}

/* Called when a file descriptor is closed. */
int kfs_flush(struct file *file)
{
        return -1;
}

/* Called when the file is about to be closed (file obj freed) */
int kfs_release(struct inode *inode, struct file *file)
{
        return 0;
}

/* Flushes the file's dirty contents to disc */
int kfs_fsync(struct file *file, struct dentry *dentry, int datasync)
{
        return -1;
}

/* Traditionally, sleeps until there is file activity.  We probably won't
 * support this, or we'll handle it differently. */
unsigned int kfs_poll(struct file *file, struct poll_table_struct *poll_table)
{
        return -1;
}

/* Reads count bytes from a file, starting from (and modifiying) offset, and
 * putting the bytes into buffers described by vector */
ssize_t kfs_readv(struct file *file, const struct iovec *vector,
                  unsigned long count, off64_t *offset)
{
        return -1;
}

/* Writes count bytes to a file, starting from (and modifiying) offset, and
 * taking the bytes from buffers described by vector */
ssize_t kfs_writev(struct file *file, const struct iovec *vector,
                  unsigned long count, off64_t *offset)
{
        return -1;
}

/* Write the contents of file to the page.  Will sort the params later */
ssize_t kfs_sendpage(struct file *file, struct page *page, int offset,
                     size_t size, off64_t pos, int more)
{
        return -1;
}

/* Checks random FS flags.  Used by NFS. */
int kfs_check_flags(int flags)
{ // default, nothing
        return -1;
}

/* Redeclaration and initialization of the FS ops structures */
struct page_map_operations kfs_pm_op = {
        kfs_readpage,
        kfs_writepage,
};

struct super_operations kfs_s_op = {
        kfs_alloc_inode,
        kfs_dealloc_inode,
        kfs_read_inode,
        kfs_dirty_inode,
        kfs_write_inode,
        kfs_put_inode,
        kfs_drop_inode,
        kfs_delete_inode,
        kfs_put_super,
        kfs_write_super,
        kfs_sync_fs,
        kfs_remount_fs,
        kfs_umount_begin,
};

struct inode_operations kfs_i_op = {
        kfs_create,
        kfs_lookup,
        kfs_link,
        kfs_unlink,
        kfs_symlink,
        kfs_mkdir,
        kfs_rmdir,
        kfs_mknod,
        kfs_rename,
        kfs_readlink,
        kfs_truncate,
        kfs_permission,
};

struct dentry_operations kfs_d_op = {
        kfs_d_revalidate,
        generic_dentry_hash,
        kfs_d_compare,
        kfs_d_delete,
        kfs_d_release,
        kfs_d_iput,
};

struct file_operations kfs_f_op_file = {
        kfs_llseek,
        generic_file_read,
        generic_file_write,
        kfs_readdir,
        kfs_mmap,
        kfs_open,
        kfs_flush,
        kfs_release,
        kfs_fsync,
        kfs_poll,
        kfs_readv,
        kfs_writev,
        kfs_sendpage,
        kfs_check_flags,
};

struct file_operations kfs_f_op_dir = {
        kfs_llseek,
        generic_dir_read,
        0,
        kfs_readdir,
        kfs_mmap,
        kfs_open,
        kfs_flush,
        kfs_release,
        kfs_fsync,
        kfs_poll,
        kfs_readv,
        kfs_writev,
        kfs_sendpage,
        kfs_check_flags,
};

struct file_operations kfs_f_op_sym = {
        kfs_llseek,
        generic_file_read,
        generic_file_write,
        kfs_readdir,
        kfs_mmap,
        kfs_open,
        kfs_flush,
        kfs_release,
        kfs_fsync,
        kfs_poll,
        kfs_readv,
        kfs_writev,
        kfs_sendpage,
        kfs_check_flags,
};

/* KFS Specific Internal Functions */

/* Need to pass path separately, since we'll recurse on it.  TODO: this recurses,
 * and takes up a lot of stack space (~270 bytes).  Core 0's KSTACK is 8 pages,
 * which can handle about 120 levels deep...  Other cores are not so fortunate.
 * Can rework this if it becomes an issue. */
static int __add_kfs_entry(struct dentry *parent, char *path,
                           struct cpio_bin_hdr *c_bhdr)
{
        char *first_slash = strchr(path, '/');  
        char dir[MAX_FILENAME_SZ + 1];  /* room for the \0 */
        size_t dirname_sz;                              /* not counting the \0 */
        struct dentry *dentry = 0;
        struct inode *inode;
        int err, retval;
        char *symname, old_end;                 /* for symlink manipulation */

        if (first_slash) {
                /* get the first part, find that dentry, pass in the second part,
                 * recurse.  this isn't being smart about extra slashes, dots, or
                 * anything like that. */
                dirname_sz = first_slash - path;
                assert(dirname_sz <= MAX_FILENAME_SZ);
                strncpy(dir, path, dirname_sz);
                dir[dirname_sz] = '\0';
                printd("Finding DIR %s in dentry %s (start: %p, size %d)\n", dir,
                       parent->d_name.name, c_bhdr->c_filestart, c_bhdr->c_filesize);
                /* Need to create a dentry for the lookup, and fill in the basic nd */
                dentry = get_dentry(parent->d_sb, parent, dir);
                /* TODO: use a VFS lookup instead, to use the dcache, thought its not a
                 * big deal since KFS currently pins all metadata. */
                dentry = kfs_lookup(parent->d_inode, dentry, 0);
                if (!dentry) {
                        printk("Missing dir in CPIO archive or something, aborting.\n");
                        return -1;
                }
                retval = __add_kfs_entry(dentry, first_slash + 1, c_bhdr);
                kref_put(&dentry->d_kref);
                return retval;
        } else {
                /* no directories left in the path.  add the 'file' to the dentry */
                printd("Adding file/dir %s to dentry %s (start: %p, size %d)\n", path,
                       parent->d_name.name, c_bhdr->c_filestart, c_bhdr->c_filesize);
                /* Init the dentry for this path */
                dentry = get_dentry(parent->d_sb, parent, path);
                // want to test the regular/natural dentry caching paths
                //dcache_put(dentry->d_sb, dentry);
                /* build the inode */
                switch (c_bhdr->c_mode & CPIO_FILE_MASK) {
                        case (CPIO_DIRECTORY):
                                err = create_dir(parent->d_inode, dentry, c_bhdr->c_mode);
                                assert(!err);
                                break;
                        case (CPIO_SYMLINK):
                                /* writing the '\0' is safe since the next entry is always still
                                 * in the CPIO (and we are processing sequentially). */
                                symname = c_bhdr->c_filestart;
                                old_end = symname[c_bhdr->c_filesize];
                                symname[c_bhdr->c_filesize] = '\0';
                                err = create_symlink(parent->d_inode, dentry, symname,
                                                     c_bhdr->c_mode & CPIO_PERM_MASK);
                                assert(!err);
                                symname[c_bhdr->c_filesize] = old_end;
                                break;
                        case (CPIO_REG_FILE):
                                err = create_file(parent->d_inode, dentry,
                                                  c_bhdr->c_mode & CPIO_PERM_MASK);
                                assert(!err);
                                ((struct kfs_i_info*)dentry->d_inode->i_fs_info)->filestart =
                                                                                                                c_bhdr->c_filestart;
                                ((struct kfs_i_info*)dentry->d_inode->i_fs_info)->init_size =
                                                                                                                c_bhdr->c_filesize;
                                break;
                        default:
                                printk("Unknown file type %d in the CPIO!",
                                       c_bhdr->c_mode & CPIO_FILE_MASK);
                                kref_put(&dentry->d_kref);
                                return -1;
                }
                inode = dentry->d_inode;
                /* Set other info from the CPIO entry */
                inode->i_uid = c_bhdr->c_uid;
                inode->i_gid = c_bhdr->c_gid;
                inode->i_atime.tv_sec = c_bhdr->c_mtime;
                inode->i_ctime.tv_sec = c_bhdr->c_mtime;
                inode->i_mtime.tv_sec = c_bhdr->c_mtime;
                inode->i_size = c_bhdr->c_filesize;
                //inode->i_XXX = c_bhdr->c_dev;                 /* and friends */
                inode->i_bdev = 0;                                              /* assuming blockdev? */
                inode->i_socket = FALSE;
                inode->i_blocks = c_bhdr->c_filesize;   /* blocksize == 1 */
                kref_put(&dentry->d_kref);
        }
        return 0;
}

/* Adds an entry (from a CPIO archive) to KFS.  This will put all the FS
 * metadata in memory, instead of having to reparse the entire archive each time
 * we need to traverse.
 *
 * The other option is to just maintain a LL of {FN, FS}, and O(n) scan it.
 *
 * The path is a complete path, interpreted from the root of the mount point.
 * Directories have a size of 0.  so do symlinks, but we don't handle those yet.
 *
 * If a directory does not exist for a file, this will return an error.  Don't
 * use the -depth flag to find when building the CPIO archive, and this won't be
 * a problem.  (Maybe) */
static int add_kfs_entry(struct super_block *sb, struct cpio_bin_hdr *c_bhdr)
{
        char *path = c_bhdr->c_filename;
        /* Root of the FS, already part of KFS */
        if (!strcmp(path, "."))
                return 0;
        return __add_kfs_entry(sb->s_mount->mnt_root, path, c_bhdr);
}

void parse_cpio_entries(struct super_block *sb, void *cpio_b)
{
        struct cpio_newc_header *c_hdr = (struct cpio_newc_header*)cpio_b;

        char buf[9] = {0};      /* temp space for strol conversions */
        size_t namesize = 0;
        int offset = 0;         /* offset in the cpio archive */
        struct cpio_bin_hdr *c_bhdr = kmalloc(sizeof(*c_bhdr), 0);
        memset(c_bhdr, 0, sizeof(*c_bhdr));

        /* read all files and paths */
        for (; ; c_hdr = (struct cpio_newc_header*)(cpio_b + offset)) {
                offset += sizeof(*c_hdr);
                if (strncmp(c_hdr->c_magic, "070701", 6)) {
                        printk("Invalid magic number in CPIO header, aborting.\n");
                        return;
                }
                c_bhdr->c_filename = (char*)c_hdr + sizeof(*c_hdr);
                namesize = cpio_strntol(buf, c_hdr->c_namesize, 8);
                printd("Namesize: %d\n", namesize);
                if (!strcmp(c_bhdr->c_filename, "TRAILER!!!"))
                        break;
                c_bhdr->c_ino = cpio_strntol(buf, c_hdr->c_ino, 8);
                c_bhdr->c_mode = (int)cpio_strntol(buf, c_hdr->c_mode, 8);
                c_bhdr->c_uid = cpio_strntol(buf, c_hdr->c_uid, 8);
                c_bhdr->c_gid = cpio_strntol(buf, c_hdr->c_gid, 8);
                c_bhdr->c_nlink = (unsigned int)cpio_strntol(buf, c_hdr->c_nlink, 8);
                c_bhdr->c_mtime = cpio_strntol(buf, c_hdr->c_mtime, 8);
                c_bhdr->c_filesize = cpio_strntol(buf, c_hdr->c_filesize, 8);
                c_bhdr->c_dev_maj = cpio_strntol(buf, c_hdr->c_dev_maj, 8);
                c_bhdr->c_dev_min = cpio_strntol(buf, c_hdr->c_dev_min, 8);
                c_bhdr->c_rdev_maj = cpio_strntol(buf, c_hdr->c_rdev_maj, 8);
                c_bhdr->c_rdev_min = cpio_strntol(buf, c_hdr->c_rdev_min, 8);
                printd("File: %s: %d Bytes\n", c_bhdr->c_filename, c_bhdr->c_filesize);
                offset += namesize;
                /* header + name will be padded out to 4-byte alignment */
                offset = ROUNDUP(offset, 4);
                c_bhdr->c_filestart = cpio_b + offset;
                /* make this a function pointer or something */
                if (add_kfs_entry(sb, c_bhdr)) {
                        printk("Failed to add an entry to KFS!\n");
                        break;
                }
                offset += c_bhdr->c_filesize;
                offset = ROUNDUP(offset, 4);
                //printk("offset is %d bytes\n", offset);
                c_hdr = (struct cpio_newc_header*)(cpio_b + offset);
        }
        kfree(c_bhdr);
}