linux-ext4 - Re: Inode ENOSPC due to recently

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Message-ID: <20200305193712.GD4747@mit.edu>
Date:   Thu, 5 Mar 2020 14:37:12 -0500
From:   "Theodore Y. Ts'o" <tytso@....edu>
To:     Jan Kara <jack@...e.cz>
Cc:     linux-ext4@...r.kernel.org
Subject: Re: Inode ENOSPC due to recently_deleted()

On Thu, Mar 05, 2020 at 06:14:31PM +0100, Jan Kara wrote:
> Hello!
> 
> Recently, I've got a bug report about ext4 driver regressing compared to
> the old ext2 driver. The problem is that the filesystem is small and they
> fill the fs (use all inodes), then delete some files, and then want to use
> the inodes for other files but recently_deleted() logic makes the freed
> inodes unusable and thus inode allocation fails with ENOSPC.
> 
> AFAIU the logic implemented by recently_deleted() is more of a preference
> than a hard rule and we should rather reuse recently deleted inodes than
> return ENOSPC. Am I right?
> 
> Also I'd note that the detection whether the inode was written out in
> recently_deleted() is very inaccurate - one of the problems is that if
> several inodes in the same inode table block are deleted, then after
> writing out that block we'll be able to reuse only one of these inodes
> because by doing that, we certainly cache and dirty the inode block and
> thus the recently_deleted() logic for other deleted inodes will start to
> apply. But I think we can just live with that if we stop making
> recently_deleted() a hard rule...

Yes, if we can't find any another inodes, rerying with
recently_deleted logic skipped makes sense.

						- Ted