On 05/13/2012 02:13 PM, Hugh Dickins wrote: > 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 > Hi all, I had a fix for this a while ago and I believe Lukas had rebased it when he was working on some punch hole optimizations, but Im not sure what happened to it after that. I think Lukas might still be working on that set? If not, I can take a peek at it again and see if I can get it updated and resent. Thx! Allison Henderson -- 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
