I was able to work around the issue with the following change to *vfs_gluster_readdir

Seems like the glfs_readdirplus_r function populates sbuf with the incorrect filesize information.  When only using glfs_readdir_r, file sizes are correct.

--- /root/rpmbuild/BUILD/samba-4.2.2/source3/modules/vfs_glusterfs.c    2015-06-03 15:10:25.161869318 -0500
+++ vfs_glusterfs.c     2015-02-24 12:59:51.000000000 -0600
@@ -389,21 +389,19 @@
        struct dirent *dirent = 0;

        if (sbuf != NULL) {
-//             ret = glfs_readdirplus_r((void *)dirp, &stat, (void *)direntbuf,
-//                                      &dirent);
-           SET_STAT_INVALID(*sbuf);
-       }
-//     } else {
+               ret = glfs_readdirplus_r((void *)dirp, &stat, (void *)direntbuf,
+                                        &dirent);
+       } else {
                ret = glfs_readdir_r((void *)dirp, (void *)direntbuf, &dirent);
-//     }
+       }

        if ((ret < 0) || (dirent == NULL)) {
                return NULL;
        }

-//     if (sbuf != NULL) {
-//             smb_stat_ex_from_stat(sbuf, &stat);
-//     }
+       if (sbuf != NULL) {
+               smb_stat_ex_from_stat(sbuf, &stat);
+       }

        return dirent;
 }

Thanks for reporting this, Jason, and for the good analysis.
Looking ...

I tried to reproduce this and was not able to.

Interestingly, I don't see SET_STAT_INVALID(*sbuf); line in any of the branches of Samba code that I have. It is visible in comment 1  here.

Is there anything I am missing?
I will try to reproduce it again.

(In reply to Raghavendra Talur from comment #3)

> Interestingly, I don't see SET_STAT_INVALID(*sbuf); line in
> any of the branches of Samba code that I have.
> It is visible in comment 1  here.

I think the diff in comment #1 is reversed, i.e. the
lines with "-" are the new state, "+" are the old state.

Removing the commented out lines ("//"), I come up with
the following diff that I think is equivalent to the
one of comment #1:

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 source3/modules/vfs_glusterfs.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/source3/modules/vfs_glusterfs.c b/source3/modules/vfs_glusterfs.c
index cfdd195..7a10948 100644
--- a/source3/modules/vfs_glusterfs.c
+++ b/source3/modules/vfs_glusterfs.c
@@ -389,12 +389,11 @@ static struct dirent *vfs_gluster_readdir(struct vfs_handle_struct *handle,
        struct dirent *dirent = 0;
 
        if (sbuf != NULL) {
-               ret = glfs_readdirplus_r((void *)dirp, &stat, (void *)direntbuf,
-                                        &dirent);
-       } else {
-               ret = glfs_readdir_r((void *)dirp, (void *)direntbuf, &dirent);
+               SET_STAT_INVALID(*sbuf);
        }
 
+       ret = glfs_readdir_r((void *)dirp, (void *)direntbuf, &dirent);
+
        if ((ret < 0) || (dirent == NULL)) {
                return NULL;
        }
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Not quite sure what to make of it yet.
Talur: we need to dig deeper...

(forgot the removal of the call to  smb_stat_ex_from_stat in the diff)

(In reply to Jason Lanclos from comment #0)
I am not able to reproduce this on current code base.

$ ls -l
total 229956
-rw-------. 1 anoopcs anoopcs 100769792 Oct 22 11:23 core.28233
-rw-r--r--. 1 anoopcs anoopcs 134700571 Oct 14 12:52 log.desktop-63em11p

$ sudo smbclient \\\\192.168.122.101\\gluster-vfs-vol -U root%smb
Try "help" to get a list of possible commands.
smb: \> cd users\
smb: \users\> put core.28233
putting file core.28233 as \users\core.28233 (69644.7 kb/s) (average 69644.7 kb/s)
smb: \users\> put log.desktop-63em11p
putting file log.desktop-63em11p as \users\log.desktop-63em11p (64895.7 kb/s) (average 66846.4 kb/s)
smb: \users\> exit

$ sudo smbclient \\\\192.168.122.101\\gluster-vfs-vol -U root%smb
Try "help" to get a list of possible commands.
smb: \> cd users\
smb: \users\> dir
  .                                   D        0  Tue Nov  5 18:54:03 2019
  ..                                  D        0  Tue Nov  5 18:45:07 2019
  core.28233                          A 100769792  Tue Nov  5 18:53:58 2019
  log.desktop-63em11p                 A 134700571  Tue Nov  5 18:54:05 2019
  anoopcs                             D        0  Tue Nov  5 11:36:55 2019

		1044984 blocks of size 1024. 762276 blocks available
smb: \users\> exit

I would suggest to close the bug report as NOTABUG.

According to Anoop, this works in the current releases.
Reopen if issue is still seen.