From: Jim Meyering Subject: Re: Files full of zeros with coreutils-8.11 and xfs (FIEMAP related?) Date: Thu, 21 Apr 2011 22:12:02 +0200 Message-ID: <87fwpbqs8d.fsf@rho.meyering.net> References: <20110414225904.GK21395@dastard> <4DA7836A.5040604@draigBrady.com> <20110415000940.GL21395@dastard> <76FFF648-CA02-494B-A862-566C66A8CB82@dilger.ca> <20110416005040.GP21395@dastard> <4EEEA16E-1FDB-4430-A372-8F8701196E4C@mit.edu> <20110418004040.GS21395@dastard> <6C89E159-A5F6-4A06-A3D2-273BE4CFB9B5@dilger.ca> <20110419025949.GA3030@thunk.org> <4DACFBEB.9040909@sandeen.net> Mime-Version: 1.0 Content-Type: text/plain Cc: Andreas Dilger , Ted Ts'o , Dave Chinner , Yongqiang Yang , xfs-oss , "coreutils-mXXj517/zsQ@public.gmane.org" , "linux-ext4-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Markus Trippelsdorf To: Eric Sandeen Return-path: In-Reply-To: <4DACFBEB.9040909-+82itfer+wXR7s880joybQ@public.gmane.org> (Eric Sandeen's message of "Mon, 18 Apr 2011 22:05:15 -0500") List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: coreutils-bounces+gcgcg-coreutils=m.gmane.org-mXXj517/zsQ@public.gmane.org Sender: coreutils-bounces+gcgcg-coreutils=m.gmane.org-mXXj517/zsQ@public.gmane.org List-Id: linux-ext4.vger.kernel.org Eric Sandeen wrote: > On 4/18/11 9:59 PM, Ted Ts'o wrote: > ... >> Maybe coreutils will need to use FIEMAP_FLAG_SYNC initially, since >> it's the only way to guarantee correct behaviour for XFS. But I would >> really rather that be the long-term way we leave things! > > XFS ... or ext4: > > # xfs_io -Ff -c "falloc 0 1m" -c "pwrite 0 512k" testfile; > /root/fiemap-test testfile > wrote 524288/524288 bytes at offset 0 > 512 KiB, 128 ops; 0.0000 sec (161.342 MiB/sec and 41303.6463 ops/sec) > start 0 length -1 flags 0x0 count 32 > ext: 0 logical: [ 0.. 255] phys: 34048.. 34303 flags: 0x801 tot: 256 > > # uname -r > 2.6.39-0.rc3.git2.0.fc16.x86_64 > > Above is on ext4. It behaves exactly like XFS in my testing; data in > the page cache does not cause fiemap to return anything other than > "unwritten" for preallocated extents. Thanks for the feedback. In case anyone wants to test or review, I've just made a coreutils snapshot: http://thread.gmane.org/gmane.comp.gnu.coreutils.general/1108