Re: 2.6.21-git10/11: files getting truncated on xfs? or maybe an nlink problem?

David Chinner
2007-05-15T00:15:08Z

On Sat, May 12, 2007 at 07:56:20AM -0700, Jeremy Fitzhardinge wrote:
> David Chinner wrote:
> > What I don't understand is that on unmount dirty xfs inodes get
> > written out. Clearly this is not happening - either there's a hole
> > in the writeback logic (unlikely - it was unchanged) or we've missed
> > some case where we need to update the filesize and mark the inode
> > dirty.
> >
> > Hmmmm - if the write was just a short append to the file, then the
> > block that was written to should already be mapped. Then we'll just
> > look up the extent by doing a BMAPI_READ lookup, set the type to
> > IOMAP_READ and add the block to ioend we are building.
> >
>
> Well, that result I mailed you showed that the difference was just over
> 16k, and that there was a 32 block difference in the final extent
> length. Does that fit with this theory?

Yes - because when we do specualtive allocation of 64k beyond EOF
by default on appends....

> > The type IOMAP_READ determines the I/O completion behaviour - in this case
> > it is xfs_end_bio_read(), which fails to update the file size....
> >
> > Bingo.
> >
> > A patch for you to try, Jeremy. I've just started a test run on it...
> >
>
> Thanks, I'll give it a spin. Have you reproduced the bug yourself?

No, not yet. I haven't had chance because I'm travelling at the moment....

Cheers,

Dave.
--
Dave Chinner
Principal Engineer
SGI Australian Software Group