Updation of number of inode links not persisted

[OmSaran]

Consider the example scenario: A new filesystem that has only /mlfs

1. Check the number of nlinks for /mlfs, it returns 1
2. Create a directory /mlfs/A
3. Check the number of nlinks again, it returns 2 (from DRAM)
4. First 3 steps run in the same process.
5. In a new program check the number of nlinks for /mlfs it returns 1 (This should be 2)

If my understanding is correct we have not persisted it during log digestion.

I attempted a fix for this here: #21

Here's the sample program I used to test it:

create.c

#include <stdio.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <assert.h>

#include <mlfs/mlfs_interface.h>

#define PARENT_DIR "/mlfs"
#define CHILD_DIR "/mlfs/A"

int main() {
    init_fs();
    int ret;
    struct stat statbuf;

    lstat(PARENT_DIR, &statbuf);
    printf("nlinks before creating = %ld\n", statbuf.st_nlink);

    ret = mkdir(CHILD_DIR, 0777);
    assert(ret == 0);

    lstat(PARENT_DIR, &statbuf);
    printf("nlinks after creating = %ld\n", statbuf.st_nlink);
    shutdown_fs();
}

check.c

#include <stdio.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <assert.h>
#include <unistd.h>

#include <mlfs/mlfs_interface.h>

#define PARENT_DIR "/mlfs"
#define CHILD_DIR "/mlfs/A"

int main() {
    init_fs();

    int ret;
    struct stat statbuf;

    ret = access(CHILD_DIR, F_OK);
    assert(ret == 0);

    printf("%s exists!\n", CHILD_DIR);

    assert(lstat(PARENT_DIR, &statbuf) == 0);
    printf("nlinks = %ld\n", statbuf.st_nlink);

    shutdown_fs();
}

[cmolder]

The access control group has had a similar issue with some custom inode params. We've been adding user/group/permission fields to the inode/stat and, although they are processed properly in-memory (e.g. mlfs_object_create) when writing to a new file, these fields revert to zero when we close and reopen the same file later. It seems like these changes aren't being conveyed to the disk during digestion.

[OmSaran]

Based on my understanding, it is updated in the cache properly in LibFS, but during digestion, some inode updates (particularly nlinks in my case) are not being captured/digested. I guess you have the same issue after adding new attributes to the inode.

If my understanding is correct, you could attempt to add corresponding updates at the same place where I have added the fix for nlinks. The PR is here: #21

[cmolder]

Implementing #21 worked for me, at least for the other fields. Thanks!

[wreda]

Thanks for the fix. This is now merged.