> > Dear ext4 devs, > > Today I hit a situation where seemingly blocks did not get written to > disk. I've narrowed it down to the following test case. > > Running Fedora Core 12 with kernel 2.6.31.9-174.fc12.x86_64, both on an > i7 920 and a Core2 Q6600, I executed the following steps: > > - create a file > - with kernel async i/o, write a 512kb (haven't tried other sizes) block > to an offset >4GB, effectively creating a large sparse file > - again with async i/o, write a 512kb block to an offset smaller than > the previous write, but >4GB > - wait for the kernel async i/o to tell you the writes have succeeded > > Now, looking at the file, the second write never seems to have happened. > When doing this on the same machines on ext3, the behavior is as expected. > > As far as I can tell (from the bigger program that triggered this), all > writes >4GB but < EOF to a sparse file with async i/o aren't executed. > When creating a large file first (i.e., with dd), everything does work > as expected. > > Attached is some C code that triggers this bug for me. > > If you need more information or want me to test some more things, please > do ask. > I ran your program on FC-11 with a 2.6.33-rc4 upstream kernel: it worked fine. Both dd's gave the expected output. Thanks, Nick Transcript: root@shifter:~/src/ext4/giel-de-nijs# ./a.out opening file ext4_bug.testfile submitting write of 524288 bytes at offset 6442450944 waiting for write to be finished got 1 events written 524288 bytes submitting write of 524288 bytes at offset 5368709120 waiting for write to be finished got 1 events written 524288 bytes root@shifter:~/src/ext4/giel-de-nijs# dd if=ext4_bug.testfile bs=512k count=1 skip=10K|hexdump 0000000 ffff ffff ffff ffff ffff ffff ffff ffff * 1+0 records in 1+0 records out 524288 bytes (524 kB) copied, 0.0045471 s, 115 MB/s 0080000 root@shifter:~/src/ext4/giel-de-nijs# dd if=ext4_bug.testfile bs=512k count=1 skip=12K|hexdump 0000000 ffff ffff ffff ffff ffff ffff ffff ffff * 1+0 records in 1+0 records out 524288 bytes (524 kB) copied, 0.00474075 s, 111 MB/s 0080000 -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
