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Date: Sun, 10 Aug 2008 12:54:00 -0500 From: Eric Sandeen <sandeen@...hat.com> To: "Theodore Ts'o" <tytso@....edu> CC: linux-ext4@...r.kernel.org Subject: Re: Bug in delayed allocation: really bad block layouts! Theodore Ts'o wrote: > Thanks to a comment on a recent blog entry of mine[1], I think I've > uncovered a rather embarassing bug in mballoc. > > [1]http://thunk.org/tytso/blog/2008/08/08/fast-ext4-fsck-times > > I created a fresh 5 gig ext4 filesystem, and then populating it using a > single-threaded tar command: > > (cd /usr ; tar cf - bin lib) | (cd /mnt; tar xfp -) > > I then unmounted the filesystem, and ran an instrumented e2fsck looking > for fragmented files, and found a whole series of fragmanted files with > the following pattern: Hm, last year I reported "delalloc fragmenting files?" and Alex sent some patches, I wonder if they all got integrated. I guess I should re-run that simple large-file dd test and see how we're doing now... ok, on a 1G single-threaded write it looks sane: Discontinuity: Block 53248 is at 100352 (was 98303) Discontinuity: Block 116736 is at 165888 (was 163839) Discontinuity: Block 180224 is at 231424 (was 229375) Discontinuity: Block 243712 is at 296960 (was 294911) so I suppose this is not the same issue ... Hm, and I tried writing out 10 files in order as a simple test but umount/remount brought me back many 0-byte files, I need to update my patchset I guess. :) -Eric -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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