On 11/29/2012 12:15 PM, Jim Meyering wrote: > Hugh Dickins wrote: >> On Thu, 29 Nov 2012, Jaegeuk Hanse wrote: > ... >>> But this time in which scenario will use it? >> >> I was not very convinced by the grep argument from Jim and Paul: >> that seemed to be grep holding on to a no-arbitrary-limits dogma, >> at the expense of its users, causing an absurd line-length issue, >> which use of SEEK_DATA happens to avoid in some cases. >> >> The cp of sparse files from Jeff and Dave was more convincing; >> but I still didn't see why little old tmpfs needed to be ahead >> of the pack. >> >> But at LinuxCon/Plumbers in San Diego in August, a more convincing >> case was made: I was hoping you would not ask, because I did not take >> notes, and cannot pass on the details - was it rpm building on tmpfs? >> I was convinced enough to promise support on tmpfs when support on >> ext4 goes in. > > Re the cp-vs-sparse-file case, the current FIEMAP-based code in GNU > cp is ugly and complicated enough that until recently it harbored a > hard-to-reproduce data-corrupting bug[*]. Now that SEEK_DATA/SEEK_HOLE > support work will work also for tmpfs and ext4, we can plan to remove > the FIEMAP-based code in favor of a simpler SEEK_DATA/SEEK_HOLE-based > implementation. How do we teach du(1) to aware of the real disk footprint with Btrfs clone or OCFS2 reflinked files if we remove the FIEMAP-based code? How about if we still keep it there, and introduce SEEK_DATA/SEEK_HOLE code to the extent-scan module which is dedicated to deal with sparse files? Thanks, -Jeff > > With the rise of virtualization, copying sparse images efficiently > (probably searching, too) is becoming more and more important. > > So, yes, GNU cp will soon use this feature. > > [*] https://plus.google.com/u/0/114228401647637059102/posts/FDV3JEaYsKD > -- > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>