linux-ext4 - Re: A bug in ext4 with big directories (was: NVFS XFS metadata)

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Message-ID: <alpine.LRH.2.02.2009230846210.1800@file01.intranet.prod.int.rdu2.redhat.com>
Date:   Wed, 23 Sep 2020 08:46:57 -0400 (EDT)
From:   Mikulas Patocka <mpatocka@...hat.com>
To:     Jan Kara <jack@...e.cz>
cc:     "Theodore Ts'o" <tytso@....edu>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        linux-ext4@...r.kernel.org,
        Dan Williams <dan.j.williams@...el.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Ira Weiny <ira.weiny@...el.com>,
        Matthew Wilcox <willy@...radead.org>,
        Eric Sandeen <esandeen@...hat.com>,
        Dave Chinner <david@...morbit.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: A bug in ext4 with big directories (was: NVFS XFS metadata)



On Wed, 23 Sep 2020, Jan Kara wrote:

> Hi!
> 
> On Wed 23-09-20 05:20:55, Mikulas Patocka wrote:
> > There seems to be a bug in ext4 - when I create very large directory, ext4 
> > fails with -ENOSPC despite the fact that there is plenty of free space and 
> > free inodes on the filesystem.
> > 
> > How to reproduce:
> > download the program dir-test: 
> > http://people.redhat.com/~mpatocka/benchmarks/dir-test.c
> > 
> > # modprobe brd rd_size=67108864
> > # mkfs.ext4 /dev/ram0
> > # mount -t ext4 /dev/ram0 /mnt/test
> > # dir-test /mnt/test/ 8000000 8000000
> > deleting: 7999000
> > 2540000
> > file 2515327 can't be created: No space left on device
> > # df /mnt/test
> > /dev/ram0        65531436 633752 61525860   2% /mnt/test
> > # df -i /mnt/test
> > /dev/ram0        4194304 1881547 2312757   45% /mnt/test
> 
> Yeah, you likely run out of space in ext4 directory h-tree. You can enable
> higher depth h-trees with large_dir feature (mkfs.ext4 -O large_dir). Does
> that help?

Yes, this helps.

Mikulas

> 
> 								Honza
> 
> -- 
> Jan Kara <jack@...e.com>
> SUSE Labs, CR