NAK, this patch doesn't handle extents that cross multiple FIEMAP calls. Digging further, the fibmap version prints some rather borken results, so I might as well fix both issues for v2. --D On Mon, Nov 30, 2015 at 04:03:10PM -0800, Darrick J. Wong wrote: > Currently, filefrag's "expected physical block" column expects extent > records to be physically adjacent regardless of the amount of logical > block space between the two records. This means that if we punch a > hole in a file, we get reports like this: > > 4: 4096.. 8343: 57376.. 61623: 4248: 55328: > 5: 8345.. 10313: 61625.. 63593: 1969: 61624: > > Notice how it expects 8345 to map to 61624, and scores this against > the fragmentation of the file. Flagging this as "unexpected" is > incorrect because the gap in the logical mapping is exactly the same > size as the gap in the physical extents. > > Furthermore, this scenario leaves the door open to the optimal mapping > -- if a write to block 8344 causes it to be mapped to 61624, the > entire range 4096-10313 can be mapped with a single extent. Until > that happens, there's no way to combine extents 4 and 5 because of the > gap in the logical mapping at block 8344. > > Therefore, tweak the extent report to account for holes. > > Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx> > --- > misc/filefrag.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/misc/filefrag.c b/misc/filefrag.c > index 5bcde91..dacdae6 100644 > --- a/misc/filefrag.c > +++ b/misc/filefrag.c > @@ -266,7 +266,12 @@ static int filefrag_fiemap(int fd, int blk_shift, int *num_extents, > print_extent_info(&fm_ext[i], n, expected, > blk_shift, st); > > - expected = fm_ext[i].fe_physical + fm_ext[i].fe_length; > + expected = fm_ext[i].fe_physical; > + if (i < fiemap->fm_mapped_extents - 1) > + expected += fm_ext[i + 1].fe_logical - > + fm_ext[i].fe_logical; > + else > + expected += fm_ext[i].fe_length; > if (fm_ext[i].fe_flags & FIEMAP_EXTENT_LAST) > last = 1; > n++; > -- > 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 -- 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
