From: Tahsin Erdogan <tahsin@google.com>
Subject: Re: [PATCH 28/28] quota: add extra inode count to dquot transfer functions
Date: Mon, 19 Jun 2017 04:46:00 -0700
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References: <20170531081517.11438-1-tahsin@google.com> <20170531081517.11438-28-tahsin@google.com>
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 <20170619090329.GE11837@quack2.suse.cz>
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Cc: Jan Kara <jack@suse.com>, "Theodore Ts'o" <tytso@mit.edu>,
        Andreas Dilger <adilger.kernel@dilger.ca>,
        Dave Kleikamp <shaggy@kernel.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Mark Fasheh <mfasheh@versity.com>,
        Joel Becker <jlbec@evilplan.org>, Jens Axboe <axboe@fb.com>,
        Deepa Dinamani <deepa.kernel@gmail.com>,
        Mike Christie <mchristi@redhat.com>,
        Fabian Frederick <fabf@skynet.be>, linux-ext4@vger.kernel.org,
        linux-kernel@vger.kernel.org, jfs-discussion@lists.sourceforge.net,
        linux-fsdevel@vger.kernel.org, ocfs2-devel@oss.oracle.com,
        reiserfs-devel@vger.kernel.org
To: Jan Kara <jack@suse.cz>
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>> I tried that approach by adding a "int get_inode_usage(struct inode
>> *inode, qsize_t *usage)" callback to dquot_operations. Unfortunately,
>> ext4 code that calculates the number of internal inodes
>> (ext4_xattr_inode_count()) is subject to failures so the callback has
>> to be able to report errors. And, that itself is problematic because
>> we can't afford to have errors in dquot_free_inode(). If you have
>> thoughts about how to address this please let me know.
>
> Well, you can just make dquot_free_inode() return error. Now most callers
> won't be able to do much with an error from dquot_free_inode() but that's
> the case also for other things during inode deletion - just handle it as
> other fatal failures during inode freeing.
>
I just checked dquot_free_inode() to see whether it calls anything
that could fail. It calls mark_all_dquot_dirty() and ignores the
return code from it. I would like to follow the same for the
get_inode_usage() as the only use case for get_inode_usage() (ext4)
should not fail at inode free time.

Basically, I want to avoid changing return type from void to int
because it would create a new responsibility for the filesystem
implementations who do not know how to deal with it.