linux-kernel - Re: [PATCH 28/28] quota: add extra inode count to dquot transfer functions

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Date:   Mon, 19 Jun 2017 04:46:00 -0700
From:   Tahsin Erdogan <tahsin@...gle.com>
To:     Jan Kara <jack@...e.cz>
Cc:     Jan Kara <jack@...e.com>, "Theodore Ts'o" <tytso@....edu>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Dave Kleikamp <shaggy@...nel.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Mark Fasheh <mfasheh@...sity.com>,
        Joel Becker <jlbec@...lplan.org>, Jens Axboe <axboe@...com>,
        Deepa Dinamani <deepa.kernel@...il.com>,
        Mike Christie <mchristi@...hat.com>,
        Fabian Frederick <fabf@...net.be>, linux-ext4@...r.kernel.org,
        linux-kernel@...r.kernel.org, jfs-discussion@...ts.sourceforge.net,
        linux-fsdevel@...r.kernel.org, ocfs2-devel@....oracle.com,
        reiserfs-devel@...r.kernel.org
Subject: Re: [PATCH 28/28] quota: add extra inode count to dquot transfer functions

>> 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.