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Old 09-03-2024, 05:01 AM   #1
ejinkas12
LQ Newbie
 
Registered: Sep 2024
Posts: 4

Rep: Reputation: 14
Unhappy FUSE does not call my 'readdir' callback

I've been trying to write a custom filesystem with fuse and I've run into a little problem. Trying to use `ls` on the mounted filesystem produced a Function not implemented error. Using the -d option helped with pinpointing the problem: FUSE thinks the readdir operation is not implemented. It just says it's not implemented
Code:
unique: 262, opcode: READDIR (28), nodeid: 1, insize: 80, pid: 4699
   unique: 262, error: -38 (Function not implemented), outsize: 16
This is the full source code:
Code:
// mkdir cd
#define FUSE_USE_VERSION 31

#include <fuse3/fuse.h>
#include <stdio.h>
#include <string.h>
#include <mkern_types.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <uuid/uuid.h>

#define printe(msg, ...) fprintf(stderr, msg, __VA_ARGS__)

struct file_handle
{
    m_bool avail;
    char *path;
    uint64_t ptr;
    mkern_fD dir;
};

struct file_handle *ftab;
uint64_t nEntries;
mkern_boot_block bblock;
mkern_fD_dir rootDir;
FILE *dev = NULL;
m_bool kernMod = m_false;

int brkStr(char *str, char **toks[], const char brkchr);
m_uint32 CalcC32(void *data, const m_size64 size);

int getFDInfo(mkern_fD *fdir, const char *path)
{
    char *pth = NULL;
    m_char8 *name = NULL;
    int nlev = 0;
    mkern_fD dir;
    char **dirstr = NULL;

    if (!strcmp("/", path))
    {
        memcpy(fdir, &rootDir, sizeof(dir));
        return 1;
    }

    if (!(name = calloc(bblock.blk_size_bs - sizeof(mkern_fD), sizeof(m_char8))))
        return 0;
    if (!(pth = strdup(path)))
    {
        free(name);
        return 0;
    }
    if (!(nlev = brkStr(pth, &dirstr, '/')))
        goto exit_fail;
    dir = *((mkern_fD *)&rootDir);

    for (int i = 1; i < nlev; i++)
    {
        fseek(dev, (bblock.rootDir_off_blk + ((mkern_fD_dir *)&dir)->fDirs) * bblock.blk_size_bs, SEEK_SET);
        fread(&dir, sizeof(dir), 1, dev);
        fread(name, bblock.blk_size_bs - sizeof(mkern_fD), 1, dev);

        while (1)
        {
            if (!strcmp(name, dirstr[i]))
            {
                if ((dir.type & MKERN_FDIR_TYPE) == MKERN_FDIR_TYPE_DIR && dir.type & MKERN_FDIR_VISIBLE | kernMod)
                    break;
                else if (i == nlev - 1 && dir.type & MKERN_FDIR_VISIBLE | kernMod)
                    break;

                goto exit_fail;
            }

            if (!dir.next_fileDir_blk)
                goto exit_fail;

            fseek(dev, (bblock.rootDir_off_blk + dir.next_fileDir_blk) * bblock.blk_size_bs, SEEK_SET);
            fread(&dir, sizeof(dir), 1, dev);
            fread(name, bblock.blk_size_bs - sizeof(mkern_fD), 1, dev);
        }
    }

    memcpy(fdir, &dir, sizeof(dir));
    free(name);
    free(pth);
    return 1;
exit_fail:
    free(name);
    free(pth);
    return 0;
}

m_uint64 reassignHandle(const char *path, mkern_fD dir)
{
    m_uint64 found = 0;

    for (uint64_t i = 0; i < nEntries; i++)
    {
        if (!strcmp(path, ftab[i].path))
            return 0;

        if (ftab[i].avail && !found)
        {
            ftab[i].avail = m_false;
            ftab[i].path = path;
            ftab[i].ptr = 0;
            ftab[i].dir = dir;
            found = i;
        }
    }

    return found;
}

m_uint64 createHandle(const char *path, mkern_fD dir)
{
    for (int i = 0; i < nEntries; i++)
    {
        if (!strcmp(path, ftab[i].path))
            return 0;
    }

    if (!(ftab = reallocarray(ftab, nEntries + 1, sizeof(struct file_handle))))
        return 0;

    ftab[nEntries].avail = m_false;
    ftab[nEntries].path = path;
    ftab[nEntries].ptr = 0;
    ftab[nEntries].dir = dir;

    nEntries++;
    return nEntries - 1;
}

int releaseHandle(struct fuse_file_info *finfo)
{
    if (!finfo)
        return 0;

    if (finfo->fh > nEntries)
        return 0;

    ftab[finfo->fh].avail = m_true;
    return 1;
}

int getHandleFDInfo(m_uint64 fh, mkern_fD *dir)
{
    if (fh > nEntries)
        return 0;

    *dir = ftab[fh].dir;
    return 1;
}

int m_readdir(const char *path, void *private_data, fuse_fill_dir_t filler, off_t off, struct fuse_file_info *finfo, enum fuse_readdir_flags flgs)
{
    mkern_fD dir;
    char name[960];
    struct stat sinf;

    printf("what's going on\n");

    if (!finfo)
        return -EINVAL;

    if ((dir.type & MKERN_FDIR_TYPE) != MKERN_FDIR_TYPE_DIR)
        return -EACCES;

    if (!getHandleFDInfo(finfo->fh, &dir))
        return -EBADF;

    fseek(dev, (bblock.rootDir_off_blk + ((mkern_fD_dir *)&dir)->fDirs) * bblock.blk_size_bs, SEEK_SET);
    memset(&sinf, 0, sizeof(sinf));

    while (1)
    {
        fread(&dir, sizeof(dir), 1, dev);

        if (!(dir.type & MKERN_FDIR_VISIBLE) && !kernMod)
            goto get_next_blk;

        fread(name, sizeof(name), 1, dev);
        sinf.st_uid = getuid();
        sinf.st_gid = getgid();
        sinf.st_atime = dir.lastAcc_time;
        sinf.st_mtime = dir.lastAcc_time;

        if ((dir.type & MKERN_FDIR_TYPE) == MKERN_FDIR_TYPE_DIR)
        {
            if (!strcmp("/", path))
                sinf.st_mode = S_IFDIR | 0755;

            sinf.st_mode = S_IFDIR | 0644;
        }
        else
        {
            sinf.st_mode = S_IFREG | 0644;
            sinf.st_size = ((mkern_fD_file *)&dir)->size_blk * 1024;
        }

        filler(private_data, name, &sinf, 0, flgs);

    get_next_blk:
        if (!dir.next_fileDir_blk)
            break;

        fseek(dev, (bblock.rootDir_off_blk + dir.next_fileDir_blk) * bblock.blk_size_bs, SEEK_SET);
    }

    return 0;
}

int m_read(const char *path, char *data, size_t size, off_t off, struct fuse_file_info *finfo)
{
    printf("as\n");
    strcpy(data, "Yeah whatever rocks your boat\n");
    return sizeof("Yeah whatever rocks your boat\n");
}

int m_getattr(const char *path, struct stat *st, struct fuse_file_info *finfo)
{
    mkern_fD inf;

    if (!path || !st)
        return -EINVAL;

    if (!getFDInfo(&inf, path))
        return -ENOENT;

    memset(st, 0, sizeof(struct stat));
    st->st_uid = getuid();
    st->st_gid = getgid();
    st->st_atime = inf.lastAcc_time;
    st->st_mtime = inf.lastAcc_time;

    if ((inf.type & MKERN_FDIR_TYPE) == MKERN_FDIR_TYPE_DIR)
    {
        if (!strcmp("/", path))
            st->st_mode = S_IFDIR | 0755;

        st->st_mode = S_IFDIR | 0644;
    }
    else
    {
        st->st_mode = S_IFREG | 0644;
        st->st_size = ((mkern_fD_file *)&inf)->size_blk * 1024;
    }

    return 0;
}

int m_create(const char *path, mode_t mode, struct fuse_file_info *finfo)
{
    char **dirstr = NULL;
    mkern_fD dir;

    if (!path || !finfo)
        return -EINVAL;

    if (getFDInfo(&dir, path))
        return EEXIST;

    if (!(finfo->fh = reassignHandle(path, dir)))
    {
        if (!(finfo->fh = createHandle(path, dir)))
            return -ENOMEM;
    }

    return 0;
}

int m_open(const char *path, struct fuse_file_info *finfo)
{
    mkern_fD dir;

    if (!path || !finfo)
        return -EINVAL;

    if (finfo->flags & O_CREAT)
        printe("can't use open to create\n", NULL);

    if (!getFDInfo(&dir, path))
        return -ENOENT;

    if ((dir.type & MKERN_FDIR_TYPE) == MKERN_FDIR_TYPE_DIR && (finfo->flags & O_ACCMODE) != O_RDONLY)
        return -EACCES;

    if (!(finfo->fh = reassignHandle(path, dir)))
    {
        if (!(finfo->fh = createHandle(path, dir)))
            return -ENOMEM;
    }

    return 0;
}

int m_release(const char *path, struct fuse_file_info *finfo)
{
    if (!path || !finfo)
        return -EINVAL;

    if (!releaseHandle(finfo))
        return -ENOENT;

    return 0;
}

int m_mkdir(const char *path, mode_t mode)
{
    return 0;
}

int m_opendir(const char *path, struct fuse_file_info *finfo)
{
    mkern_fD dir;

    if (!path || !finfo)
        return -EINVAL;

    if (!getFDInfo(&dir, path))
        return -ENOENT;

    if ((dir.type & MKERN_FDIR_TYPE) != MKERN_FDIR_TYPE_DIR)
        return -EACCES;

    if (!(finfo->fh = reassignHandle(path, dir)))
    {
        if (!(finfo->fh = createHandle(path, dir)))
            return -ENOMEM;
    }

    return 0;
}

int m_releasedir(const char *path, struct fuse_file_info *finfo)
{
    if (!path || !finfo)
        return -EINVAL;

    if (!releaseHandle(finfo))
        return -ENOENT;

    return 0;
}

void *m_init()
{
    return NULL;
}

struct fuse_operations fo = {
    .open = m_open,
    .release = m_release,
    .readdir = m_readdir,
    .read = m_read,
    .getattr = m_getattr,
    .create = m_create,
    .opendir = m_opendir,
    .releasedir = m_releasedir,
    .mkdir = m_mkdir,
    .init = m_init,
};

int main(int argc, char **argv)
{
    char *args[6];
    mkern_fD atab;

    if (argc < 3)
    {
        printe("msh: incorrect usage\n", NULL);
        return -1;
    }

    if (!(dev = fopen(argv[1], "r+")))
    {
        printe("could not open %s\n", argv[1]);
        return -1;
    }

    fread(&bblock, sizeof(bblock), 1, dev);
    fseek(dev, bblock.rootDir_off_blk * bblock.blk_size_bs, SEEK_SET);
    fread(&rootDir, sizeof(rootDir), 1, dev);

    ftab = calloc(4, sizeof(struct file_handle));
    kernMod = m_true;
    if (!getFDInfo(&atab, "/allocTab"))
    {
        printe("something is wrong\n", NULL);
        return -1;
    }
    kernMod = m_false;

    ftab[3].dir = atab;
    ftab[3].path = "/allocTab";
    nEntries = 4;

    if (bblock.checksum != CalcC32(&bblock, sizeof(bblock) - 4))
    {
        printe("boot block corrupted\n", NULL);
        return -1;
    }

    args[0] = argv[0];
    args[1] = "-f";
    args[2] = argv[2];
    args[3] = "-d";
    args[4] = "-oauto_unmount";
    args[5] = "-s";

    return fuse_main(6, args, &fo, NULL);
}

m_uint32 CalcC32(void *data, const m_size64 size)
{
    m_uint32 b, crc = 0xffffffff, mask;
    m_byte *bs = (m_byte *)data;

    for (m_size64 i = 0; i < size; i++)
    {
        b = bs[i];
        crc ^= b;
        for (m_size64 j = 0; j < 8; j++)
        {
            mask = -(crc & 1);
            crc = (crc >> 1) ^ (0xedb88320 & mask);
        }
    }

    return ~crc;
}

int brkStr(char *str, char **toks[], const char brkchr)
{
    char **tmp = NULL;
    int n = 0;

    if (!(str && toks && brkchr))
        return 0;

    for (int i = 0;; i++)
    {
        if (!tmp || !tmp[n])
        {
            tmp = reallocarray(tmp, n + 2, sizeof(char *));
            tmp[n] = &str[i];
            tmp[n + 1] = NULL;
        }

        if (str[i] == brkchr)
        {
            str[i] = 0;
            n++;
        }
        else if (!str[i])
        {
            n++;
            break;
        }
    }

    *toks = tmp;
    return n;
}
Last edited by ejinkas12; 09-03-2024 at 09:10 AM.
 
Old 09-03-2024, 05:17 AM   #2
NevemTeve
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Can it be your code that doesn't implement readdir? (readdir field of fuse_operations structure)
Code:
asm-generic/errno.h: #define ENOSYS          38      /* Function not implemented */
Last edited by NevemTeve; 09-03-2024 at 05:23 AM.
 
Old 09-03-2024, 05:28 AM   #3
ejinkas12
LQ Newbie
 
Registered: Sep 2024
Posts: 4

Original Poster
Rep: Reputation: 14
I implemented the callback actually.
Code:
int m_readdir(const char *path, void *private_data, fuse_fill_dir_t filler, off_t off, struct fuse_file_info *finfo, enum fuse_readdir_flags flgs)
{
    mkern_fD dir;
    char name[960];
    struct stat sinf;

    printf("what's going on\n");

    if (!finfo)
        return -EINVAL;

    if ((dir.type & MKERN_FDIR_TYPE) != MKERN_FDIR_TYPE_DIR)
        return -EACCES;

    if (!getHandleFDInfo(finfo->fh, &dir))
        return -EBADF;

    fseek(dev, (bblock.rootDir_off_blk + ((mkern_fD_dir *)&dir)->fDirs) * bblock.blk_size_bs, SEEK_SET);
    memset(&sinf, 0, sizeof(sinf));

    while (1)
    {
        fread(&dir, sizeof(dir), 1, dev);

        if (!(dir.type & MKERN_FDIR_VISIBLE) && !kernMod)
            goto get_next_blk;

        fread(name, sizeof(name), 1, dev);
        sinf.st_uid = getuid();
        sinf.st_gid = getgid();
        sinf.st_atime = dir.lastAcc_time;
        sinf.st_mtime = dir.lastAcc_time;

        if ((dir.type & MKERN_FDIR_TYPE) == MKERN_FDIR_TYPE_DIR)
        {
            if (!strcmp("/", path))
                sinf.st_mode = S_IFDIR | 0755;

            sinf.st_mode = S_IFDIR | 0644;
        }
        else
        {
            sinf.st_mode = S_IFREG | 0644;
            sinf.st_size = ((mkern_fD_file *)&dir)->size_blk * 1024;
        }

        filler(private_data, name, &sinf, 0, flgs);

    get_next_blk:
        if (!dir.next_fileDir_blk)
            break;

        fseek(dev, (bblock.rootDir_off_blk + dir.next_fileDir_blk) * bblock.blk_size_bs, SEEK_SET);
    }

    return 0;
}

struct fuse_operations fo = {
    .open = m_open,
    .release = m_release,
    .readdir = m_readdir,
    .read = m_read,
    .getattr = m_getattr,
    .create = m_create,
    .opendir = m_opendir,
    .releasedir = m_releasedir,
    .mkdir = m_mkdir,
    .init = m_init,
};
 
Old 09-03-2024, 05:47 AM   #4
pan64
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it is not enough (to create a function) but you need to tell the system to use it. (that means you need to set the callback to this function).
 
Old 09-03-2024, 09:10 AM   #5
ejinkas12
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Registered: Sep 2024
Posts: 4

Original Poster
Rep: Reputation: 14
Please look at the code again. I called fuse_main and passed the fuse_operations structure fo which has the callback for readdir.
 
Old 09-03-2024, 09:19 AM   #6
pan64
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"function not implemented" means the callback points to the default handler, which will print this message.
 
Old 09-04-2024, 12:23 PM   #7
ejinkas12
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Registered: Sep 2024
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Well, this is embarrassing. Turns out that the reason everything was going haywire was because I used `pkg-config fuse --libs --cflags` when compiling instead of `pkg-config fuse3 --libs --cflags`. I think this should serve as a deterrent to me to include the compilation command I used next time.
 
4 members found this post helpful.
Old 09-04-2024, 12:39 PM   #8
pan64
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don't worry, you found it. That is the most important thing.
 
1 members found this post helpful.
Old 09-04-2024, 12:44 PM   #9
astrogeek
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Quote:
Originally Posted by ejinkas12 View Post
Well, this is embarrassing. Turns out that the reason everything was going haywire was because I used `pkg-config fuse --libs --cflags` when compiling instead of `pkg-config fuse3 --libs --cflags`. I think this should serve as a deterrent to me to include the compilation command I used next time.
We all do it!

Thanks for returning to update the thread, and a belated, "Welcome to LQ and the Programming forum"!
 
  


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