On Thu, 12 Jan 2012, Allison Henderson wrote: > On 01/11/2012 07:55 PM, Dave Chinner wrote: > > 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. > > Oh I see, I'll take a look at it, I think it will be ok to just take out the > early return. Thx! I see the -EOPNOTSUPPs have gone into 3.4's ext4_punch_hole() - thanks - but the i_size issue remains unfixed. I wouldn't be surprised if it were more complicated than you had hoped - I had no intention of trying a patch myself! It's not an actual problem for me, but I thought I'd just send a reminder, before I move out of the hole-punching business. Hugh -- 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
