From: "Darrick J. Wong" <darrick.wong@oracle.com>
To: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Matthew Wilcox <willy@infradead.org>,
"Theodore Ts'o" <tytso@mit.edu>,
linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org,
Parisc List <linux-parisc@vger.kernel.org>
Subject: Re: Question about ext4 testing: need to produce a high depth extent tree to verify mapping code
Date: Fri, 5 Jul 2019 14:40:58 -0700 [thread overview]
Message-ID: <20190705214058.GD5161@magnolia> (raw)
In-Reply-To: <1562352542.2953.10.camel@HansenPartnership.com>
On Fri, Jul 05, 2019 at 11:49:02AM -0700, James Bottomley wrote:
> On Fri, 2019-07-05 at 10:39 -0700, Matthew Wilcox wrote:
> > On Fri, Jul 05, 2019 at 09:25:48AM -0700, James Bottomley wrote:
> > > Now the problem: I'd like to do some testing with high depth extent
> > > trees to make sure I got this right, but the files we load at boot
> > > are ~20MB in size and I'm having a hard time fragmenting the
> > > filesystem enough to produce a reasonable extent (I've basically
> > > only got to a two level tree with two entries at the top). Is
> > > there an easy way of producing a high depth extent tree for a 20MB
> > > file?
> >
> > Create a series of 4kB files numbered sequentially, each 4kB in size
> > until you fill the partition. Delete the even numbered ones. Create
> > a 20MB file.
>
> Well, I know *how* to do it ... I was just hoping, in the interests of
> creative laziness, that someone else had produced a script for this
> before I had to ... particularly one which leaves more randomized gaps.
If you don't care about the contents of the file you could just build
src/punch-alternating.c from xfstests and use it to turn your 20M file
into holy cheese.
(Granted if you actually need 5,120 extents then you probably ought to
make it a 40M file and /then/ run it through the cheese grater....)
--D
> James
>
next prev parent reply other threads:[~2019-07-05 21:43 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-01 22:44 [BUG] mke2fs produces corrupt filesystem if badblock list contains a block under 251 James Bottomley
2019-07-02 0:23 ` Theodore Ts'o
2019-07-02 0:53 ` James Bottomley
2019-07-02 17:33 ` Theodore Ts'o
2019-07-02 19:31 ` James Bottomley
2019-07-02 20:39 ` Theodore Ts'o
2019-07-03 0:37 ` James Bottomley
2019-07-05 16:25 ` Question about ext4 testing: need to produce a high depth extent tree to verify mapping code James Bottomley
2019-07-05 17:39 ` Matthew Wilcox
2019-07-05 18:49 ` James Bottomley
2019-07-05 21:40 ` Darrick J. Wong [this message]
2019-07-06 4:02 ` Theodore Ts'o
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