On Wed, Jan 11, 2012 at 05:02:12PM -0800, Hugh Dickins wrote: > Hi Allison, > > In thinking about fallocate() on tmpfs, I cross-check with ext4 > and find this bug in its implementation of FALLOC_FL_PUNCH_HOLE: > > rm -f temp > fallocate -l 4096 temp > du temp # shows 4, right > fallocate -p -l 4096 temp > du temp # shows 0, right > rm -f temp > fallocate -n -l 4096 temp > du temp # shows 4, right > fallocate -p -l 4096 temp > du temp # shows 4, wrong > rm temp > > ext4_ext_punch_hole() contains /* No need to punch hole beyond i_size */ > early return, and trimming to i_size below, but forgets that the other > variety of fallocate(), with FALLOC_FL_KEEP_SIZE set, may have allocated > blocks beyond i_size. They can be removed with ftruncate(), but it is > unexpected for fallocate() not to undo its own work, and xfs does so. I'm pretty sure that's a bug as XFS allows punching holes in extents beyond EOF. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- 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
