Date: Sat, 16 Jun 2012 12:37:58 -0700 From: Xin LI <delphij@gmail.com> To: Chris Rees <utisoft@gmail.com> Cc: Wojciech Puchar <wojtek@wojtek.tensor.gdynia.pl>, freebsd-hackers@freebsd.org Subject: Re: BIO_DELETE equivalent for file on FFS filesystem Message-ID: <CAGMYy3sWPMCnttUtJhJCFTtPtgfWWUO1tgK%2BRYOE3QQpg=%2Bw1A@mail.gmail.com> In-Reply-To: <CADLo83-T%2B4W2aUKc=-CEUrOqwCq5aqipt-fK=BBboQVNJ3qcWQ@mail.gmail.com> References: <alpine.BSF.2.00.1205261704590.70782@wojtek.tensor.gdynia.pl> <4FD94240.6060806@delphij.net> <alpine.BSF.2.00.1206140647080.72545@wojtek.tensor.gdynia.pl> <CADLo83-T%2B4W2aUKc=-CEUrOqwCq5aqipt-fK=BBboQVNJ3qcWQ@mail.gmail.com>
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On Sat, Jun 16, 2012 at 12:01 PM, Chris Rees <utisoft@gmail.com> wrote: > On Jun 14, 2012 5:49 AM, "Wojciech Puchar" <wojtek@wojtek.tensor.gdynia.pl> > wrote: >>>> >>>> file to take 900MB or... can i call some system function to "punch" >>>> holes? >>> >>> >>> I think you can only truncate the file at this time, pretty much like >>> brk() works for memory. >> >> >> >> BAD. suppose i keep windoze VM image on filesystem which takes 10GB but > uses 5GB. >> >> i could write simple program to find out what blocks are unused and > then...do nothing. >> > > What if you cp it? That would be a dd(1) unless we teach cp(1) how to do sparse. I think what he wanted is to tell the OS "I don't need block XX - YY anymore" and the OS creates a sparse hole, which is not available at this time. Cheers, -- Xin LI <delphij@delphij.net> https://www.delphij.net/ FreeBSD - The Power to Serve! Live free or die
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