On Thu 05-03-09 13:55:43, Nick Piggin wrote: > On Thursday 05 March 2009 04:50:31 Jan Kara wrote: > > On Wed 04-03-09 16:55:35, Jan Kara wrote: > > > On Wed 04-03-09 15:51:09, Jan Kara wrote: > > > > first, I'd like to point out that this has happened under UML so it > > > > can be just some obscure bug in that architecture but I belive it's > > > > worth debugging anyway. Now to the problem: > > > > This has happened with today Linus's git snapshot. The filesystem is > > > > ext3 with *1KB* blocksize. I booted UML with 64MB of memory and run > > > > (these are test's from Andrew Morton's torture tests): > > > > fsx-linux -l 8000000 /mnt/testfile > > > > bash-shared-mapping -t 8 /mnt/bashfile 50000000 > > > > (the second test just makes the UML under memory pressure and stresses > > > > the filesystem, otherwise it does not interact with fsx-linux in any > > > > way). After some time (like an hour) fsx-linux reported the file is > > > > corrupted. I tried again and it happened again so probably some > > > > debugging should be possible. > > > > Both times it seems we've simply completely lost a write which > > > > happened through mmap (2 pages in the first case, 3 pages in the second > > > > case). Also I've checked and in the first case no blocks are allocated > > > > for the offsets where the data should be so most probably we've lost > > > > the write before block_write_full_page() called get_block(). > > > > I'll debug this further but I wanted let people know there's some > > > > problem and maybe somebody has some bright idea :). I'm attaching the > > > > log from fsx if someone is interested. > > > > > > Testing a bit more, I managed to reproduce the problem on ext2 and > > > what's more strange, now the lost page was written via ordinary write() > > > (fsxlog attached). So I believe this is more likely to be UML specific... > > > > And to add even more information, this also happens on ext2 with 4KB > > blocksize (although much more rarely it seems). Again the data was written > > by an extending write() but the block for it was not even allocated... > > What block device driver are you using? UML was just using image file to back the filesystem I was testing on. But I don't think that plays a big role because the blocks were not even allocated in the fs-image so we must have lost them quite early. > Can it be reproduced without mapped reads and writes completely? (-W -R) Good idea, will try. Honza -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- 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
