linux-ext4 - Re: [PATCH v3 01/10] ovl: Reject mounting case-insensitive filesystems

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Date: Thu, 25 Jan 2024 13:55:00 -0300
From: Gabriel Krisman Bertazi <krisman@...e.de>
To: Eric Biggers <ebiggers@...nel.org>
Cc: viro@...iv.linux.org.uk,  jaegeuk@...nel.org,  tytso@....edu,
  linux-ext4@...r.kernel.org,  linux-f2fs-devel@...ts.sourceforge.net,
  linux-fsdevel@...r.kernel.org,  amir73il@...il.com
Subject: Re: [PATCH v3 01/10] ovl: Reject mounting case-insensitive filesystems

Eric Biggers <ebiggers@...nel.org> writes:

> On Fri, Jan 19, 2024 at 03:47:33PM -0300, Gabriel Krisman Bertazi wrote:
>> ovl: Reject mounting case-insensitive filesystems
>
> Overlayfs doesn't mount filesystems.  I think you might mean something like
> reject case-insensitive lowerdirs?

uppers and workdir too. I'd make this:

  "ovl: Reject mounting over case-insensitive filesystems"

>
>> +	/*
>> +	 * Root dentries of case-insensitive filesystems might not have
>> +	 * the dentry operations set, but still be incompatible with
>> +	 * overlayfs.  Check explicitly to prevent post-mount failures.
>> +	 */
>> +	if (sb_has_encoding(path->mnt->mnt_sb))
>> +		return invalfc(fc, "case-insensitive filesystem on %s not supported", name);
>
> sb_has_encoding() doesn't mean that the filesystem is case-insensitive.  It
> means that the filesystem supports individual case-insensitive
> directories.
>
> With that in mind, is this code still working as intended?
>

Yes, it is. In particular, after the rest of the patchset, any dentry
will be weird and lookups will throw -EREMOTE.

> If so, can you update the comment and error message accordingly?

I'm not sure how to change and still make it readable by users.  How about:

  return invalfc(fc, "case-insensitive capable filesystem on %s not supported", name);

what do you think?

-- 
Gabriel Krisman Bertazi