On Fri, Jul 25, 2014 at 4:04 AM, Andreas Dilger <adilger@xxxxxxxxx> wrote: > > On Jul 24, 2014, at 1:22 PM, David Sterba <dsterba@xxxxxxx> wrote: >> On Thu, Jul 17, 2014 at 12:07:57AM -0600, Andreas Dilger wrote: >>> any progress on this patch series? >> >> I'm sorry I got distracted at the end of year and did not finish the >> series. >> >>> I never saw an updated version of this patch series after the last round of >>> reviews, but it would be great to move it forward. I have filefrag patches >>> in my e2fsprogs tree waiting for an updated version of your patch. >>> >>> I recall the main changes were: >>> - add FIEMAP_EXTENT_PHYS_LENGTH flag to indicate if fe_phys_length was valid >> >> fe_phys_length will be always valid, so other the flags are set only if it's >> not equal to the logical length. >> >>> - rename fe_length to fe_logi_length and #define fe_length fe_logi_length >>> - always fill in fe_phys_length (= fe_logi_length for uncompressed files) >>> and set FIEMAP_EXTENT_PHYS_LENGTH whether the extent is compressed or not >> >> This is my understanding and contradicts the first point. > > I think Dave Chinner's former point was that having fe_phys_length validity > depend on FIEMAP_EXTENT_DATA_COMPRESSED is a non-intuitive interface. It is > not true that fe_phys_length would always be valid, since that is not the > case for older kernels that currently always set this field to 0, so they > need some flag to indicate if fe_phys_length is valid. Alternately, > userspace could do: > > if (ext->fe_phys_length == 0) > ext->fe_phys_length = ext->fe_logi_length; > > but that pre-supposes that fe_phys_length == 0 is never a valid value when > fe_logi_length is non-zero, and this might introduce errors in some cases. > I could imagine that some compression methods might not allocate any space > at all if it was all zeroes, and just store a bit in the blockpointer or > extent, so having a separate FIEMAP_EXTENT_PHYS_LENGTH is probably safer > in the long run. zfs is an example of this. > That opens up the question of whether a written zero > filled space that gets compressed away is different from a hole, but I'd > prefer to just return whatever the file mapping is than interpret it. > > Cheers, Andreas > >>> - add WARN_ONCE() in fiemap_fill_next_extent() as described below >>> >>> I don't know if there was any clear statement about whether there should be >>> separate FIEMAP_EXTENT_PHYS_LENGTH and FIEMAP_EXTENT_DATA_COMPRESSED flags, >>> or if the latter should be implicit? Probably makes sense to have separate >>> flags. It should be fine to use: >>> >>> #define FIEMAP_EXTENT_PHYS_LENGTH 0x00000010 >>> >>> since this flag was never used. >> >> I've kept only FIEMAP_EXTENT_DATA_COMPRESSED, I don't see a need for >> FIEMAP_EXTENT_PHYS_LENGTH and this would be yet another flag because the >> FIEMAP_EXTENT_DATA_ENCODED is also implied. >> >> I'll send V4, we can discuss the PHYS_LENGTH flag then. > > > Cheers, Andreas > > > > > Regards, Rohan -- 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
