hammer2: ls reports "No such file or directory"

[Aleksej Lebedev]

Yes, indeed. Checking dmesg should be the first thing of course. And I do see errors there:

hammer2_bulkfree: Scanning BACKUP
chain 0000004186d3400a.01 (Inode) meth=32 CHECK FAIL (flags=00144002, bref/data ac9f8ef29097a55b/05e63f87e50fb2e2)
   Resides at/in inode 49686
   In pfs UNKNOWN on device serno/WCJ35GE0.s1d

No CRC errors though, but I will check the media anyway.

Thanks for the hint on how to repair the directory.

While here, unrelated question. On my server I have a hardware raid (LSI MegaSAS Gen2) without battery. By default write cache was enabled. Do I understand it right that it's not safe to have write cache enabled unless there is a battery? What kind of cache is that anyway. I guess if it's an nvm then maybe it's ok? Another thing: the drive write chache is set to "default" which might mean that it's on too? The drives cache is probably a volatile memory - so it's definitely should be off, right?

--
Aleksej Lebedev

On Mon, Oct 12, 2020, at 20:19, Matthew Dillon wrote:
> Generally speaking this error occurs if a directory entry is present but the related inode cannot be found.  You can use a hammer2 directive to destroy the directory entry to clean it up.  But before you do so you want to check the media for CHECK FAIL errors.
> 
> The easiest way to do this is to just read off the entire directory structure with tar, e.g. 'tar cf /dev/null filesystem' and then check the dmesg output for errors.  'dmesg | fgrep CHECK'.  Something like that.
> 
> If the filesystem appears clean other than the disconnected directory entry, then you can use 'hammer2 destroy filename' to destroy the directory entry.  Be very careful when doing that.
> 
> If the filesystem has other problems, such as CRC errors, other CHECK errors, etc.... then it is best to make a full backup and reformat.
> 
> Also make sure that bulkfree runs don't have errors.  'hammer2 bulkfree ...' and then check dmesg output as well.
> 
> --
> 
> In terms of how a disconnected inode can happen.  It has become more rare but it might still be possible if a power failure or panic occurs during heavy filesystem activity.  It shouldn't be possible for CRC errors to occur unless the media itself corrupted the data.
> 
> -Matt
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