So this coreutils test is failing on XFS: http://git.sv.gnu.org/gitweb/?p=coreutils.git;a=blob;f=tests/dd/sparse.sh;h=06efc7017 Specifically the last hole check on line 66. In summary what's happening is that a write(1MiB), lseek(1MiB), write(1MiB) creates only a 64KiB hole. Is that expected? Now a 1MiB hole is supported using truncate: dd if=/dev/urandom of=file.in bs=1M count=1 iflag=fullblock truncate -s+1M file.in dd if=/dev/urandom of=file.in bs=1M count=1 iflag=fullblock conv=notrunc oflag=append $ du -k file.in 2048 file.in But when trying to create the 1MiB hole with dd (lseek) it fails? # Create 3MiB input file file $ dd if=/dev/urandom of=file.in bs=1M count=3 iflag=fullblock $ dd if=/dev/zero of=file.in bs=1M count=1 seek=1 conv=notrunc $ du -k file.in 3072 file.in # Convert to 1MiB hole doesn't work :( $ dd if=file.in of=file.out bs=1M conv=sparse $ du -k file.out 3008 file.out # Again with syscall details: $ strace -e write,lseek dd if=file.in of=file.out bs=1M conv=sparse write(1, "...", 1048576) = 1048576 lseek(1, 1048576, SEEK_CUR) = 2097152 write(1, "...", 1048576) = 1048576 So it seems that the lseeks are treated differently to the truncate that was done in the first example, which is surprising. If we look at the file layout we can see the hole is only at the last 64KiB of the middle 1MiB of zeros, rather than for the whole middle 1MiB as in the first example?? $ filefrag -v file.out Filesystem type is: 58465342 File size of file.out is 3145728 (768 blocks of 4096 bytes) ext: logical_offset: physical_offset: length: expected: flags: 0: 0.. 495: 31271.. 31766: 496: 1: 512.. 767: 31783.. 32038: 256: 31767: eof thanks, Pádraig. Versions etc. in case useful $ uname -a Linux tp2 3.12.6-300.fc20.x86_64 #1 SMP Mon Dec 23 16:44:31 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux $ xfs_info . meta-data=/dev/loop2 isize=256 agcount=4, agsize=65536 blks = sectsz=512 attr=2 data = bsize=4096 blocks=262144, imaxpct=25 = sunit=0 swidth=0 blks naming =version 2 bsize=4096 ascii-ci=0 log =internal bsize=4096 blocks=2560, version=2 = sectsz=512 sunit=0 blks, lazy-count=1 realtime =none extsz=4096 blocks=0, rtextents=0 _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
