Hi @Hmpf, Thanks for filing a bug report.
I had a look at the changes between 5.4.0-70-generic and 5.4.0-71-generic, and I found three patches for CIFS: $ git log --grep "cifs" Ubuntu-5.4.0-70.78..Ubuntu-5.4.0-71.79 https://paste.ubuntu.com/p/YgrZcN8B6j/ I had a read of the patches, and I think that this one is causing problems for you. commit 21b200d091826a83aafc95d847139b2b0582f6d1 Author: Aurelien Aptel <aap...@suse.com> Date: Fri Feb 5 15:42:48 2021 +0100 Subject: cifs: report error instead of invalid when revalidating a dentry fails Link: https://github.com/torvalds/linux/commit/21b200d091826a83aafc95d847139b2b0582f6d1 This was backported to 5.4.0-71-generic through upstream stable in the below patch: https://paste.ubuntu.com/p/8FWhRNr8KW/ Now, I think it is that commit due to the error message you are seeing: CIFS VFS: cifs_read_super: get root inode failed The commit changes how errors are passed back to the VFS. What it did before was just return 0 (invalid) on any error at all, when cifs_revalidate_dentry() failed. What it does now is send 0 on ENOENT and ESTALE, and the actual error number on any other error. I think you are getting an "other" error, and cifs isn't sure what to do with it. Now, looking at cifs_read_super(), where the error message came from: 150 static int 151 cifs_read_super(struct super_block *sb) 152 { ... 205 rc = super_setup_bdi(sb); 206 if (rc) 207 goto out_no_root; ... 213 inode = cifs_root_iget(sb); 214 215 if (IS_ERR(inode)) { 216 rc = PTR_ERR(inode); 217 goto out_no_root; 218 } ... 225 sb->s_root = d_make_root(inode); 226 if (!sb->s_root) { 227 rc = -ENOMEM; 228 goto out_no_root; 229 } ... 240 out_no_root: 241 cifs_dbg(VFS, "%s: get root inode failed\n", __func__); 242 return rc; 243 } We see the out_no_root label is really just a catch-all error handler, and doesn't really tell us what happened, or try to handle the error. Looking at the code added by the commit, it added a new debug string: 737 static int 738 cifs_d_revalidate(struct dentry *direntry, unsigned int flags) 739 { ... 751 rc = cifs_revalidate_dentry(direntry); 752 if (rc) { 753 cifs_dbg(FYI, "cifs_revalidate_dentry failed with rc=%d", rc); We can use this string to see what the actual error is, but it is turned off by default, which is why it doesn't appear in dmesg. Would you be able to turn on this extra error message so we can keep helping you to figure out what is happening? You can turn on extra debugging with instruction from: https://wiki.samba.org/index.php/LinuxCIFS_troubleshooting 1) sudo -s 2) echo 'module cifs +p' > /sys/kernel/debug/dynamic_debug/control 3) echo 'file fs/cifs/* +p' > /sys/kernel/debug/dynamic_debug/control 4) echo 7 > /proc/fs/cifs/cifsFYI 5) exit Then, try your mount command and then try ls on that dentry file. If you check dmesg, you will get much more logging. What we are interested in will be a line with "cifs_revalidate_dentry failed with rc" and then an error number. We can then look up what the number is, and try go from there. The easiest way to turn off the extra debug logging is to reboot your system. Or you can run: 1) sudo -s 2) echo 0 > /proc/fs/cifs/cifsFYI 3) exit But rebooting is probably easier for you. Attach your new dmesg to the launchpad bug, and I will have a look. You might want to remove the URL of your company cifs share and any usernames before you upload. Let me know if you have any questions. Thanks, Matthew ** Tags added: seg -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1923670 Title: CIFS DFS entries not accessible with 5.4.0-71.74-generic To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1923670/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
