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 >
