The change was deliberate, because under some extreme circumstances you could end up corrupting the file system image when resize2fs aborted in the middle of a shrink operation. This tends to make some users cranky when they lose their data.
If you had bothered to read the entire git commit description, you would have gotten a lot more context: resize2fs: refine minimum required blocks for flex_bg file systems The previous commit exposed bugs in the calculation for flex_bg file systems. The problem is that since (by default) we keep the metadata blocks for the flex_bg in the first block group of the flex_bg, and because we don't want to overwrite metadata blocks used by the original file system with data blocks make life easier in case the resize is aborted for some reason, we need to treat all of the metadata blocks in the existing flex_bg has in use for the purposes of calculate_minimum_resize_size(). Even though this means we need to reserve more data blocks to avoid running out of space, the net result of these two commits is a net savings in how much we can shrink a file system. Using the following test sequence: mke2fs -F -t ext4 /tmp/foo.img 2T resize2fs -M /tmp/foo.img resize2fs -M /tmp/foo.img resize2fs -M /tmp/foo.img Here is the comparison in the resulting file systems between the old and new resize2fs (units are in 4k blocks): resize #1 resize #2 resize #3 old resize2fs 1117186 45679 43536 new resize2fs 48784 37413 37392 Signed-off-by: "Theodore Ts'o" <ty...@mit.edu> Note that using resize2fs -M multiple times will result in a file system which is *not* optimized for speed. In fact, it can be really bad for slow devices, such as CD-ROM's and Amazon Elastic Block devices, since files and directories will end up getting fragmented and where the data blocks can end up getting placed farther than optimal from the inode table locations. -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to e2fsprogs in Ubuntu. https://bugs.launchpad.net/bugs/1415077 Title: resize2fs -P minimum size differs greatly between v1.42.10 and v1.42.9 Status in e2fsprogs package in Ubuntu: Invalid Bug description: I have a disk image created as part of lp:maas-images. This process takes a cloud image (http://cloud-images.ubuntu.com) such as http://cloud-images.ubuntu.com/trusty/current/trusty-server-cloudimg-amd64.tar.gz . Inside that .tar.gz is a .img file. The .img file is operated on by loop mount, chroot, apt-get install and other changes. Immediately upon download and extraction of a pristine image, resize2fs output on trusty, utopic and vivid differ. A summary of differences: a.) 'resize2fs -P' on trusty (1.42.9) : 230329 utopic (1.42.10): 236103 vivid (1.42.12): 236103 b.) vivid resize2fs requires running 'e2fsck -f' first. I do realize that 'resize2fs -P' reports "Estimated minumum size" and that a difference of ~6k blocks doesn't seem like too big of a deal, but I'm seeing this behavior on a much grander scale after doing some loop mount operations on the disk image as part of the maas-images build process (lp:maas-images). On that derived image, I see 'resize2fs -P' numbers like: trusty: 274500 utopic: 358400 vivid: 358400 The 83900 blocks out of a 358400 seems significant (23% of the fs size), and results in the image appearing full on utopic/vivid, even though a mount and df show only 74% full. See below for more information. ## The original image as downloaded. $ wget http://cloud-images.ubuntu.com/releases/14.04/release-20150123/ubuntu-14.04-server-cloudimg-amd64.tar.gz $ tar -Sxvzf ubuntu-14.04-server-cloudimg-amd64.tar.gz $ md5sum trusty-server-cloudimg-amd64.img 9fd4790c920aaeb0b503ebd2bf7f383c trusty-server-cloudimg-amd64.img ## Trusty $ resize2fs -P trusty-server-cloudimg-amd64.img resize2fs 1.42.9 (4-Feb-2014) Estimated minimum size of the filesystem: 230329 $ dumpe2fs trusty-server-cloudimg-amd64.img | pastebinit dumpe2fs 1.42.9 (4-Feb-2014) http://paste.ubuntu.com/9898743/ ## Utopic $ resize2fs -P trusty-server-cloudimg-amd64.img resize2fs 1.42.10 (18-May-2014) Estimated minimum size of the filesystem: 236103 $ dumpe2fs trusty-server-cloudimg-amd64.img | pastebinit dumpe2fs 1.42.10 (18-May-2014) http://paste.ubuntu.com/9898789/ ## Vivid $ resize2fs -P trusty-server-cloudimg-amd64.img resize2fs 1.42.12 (29-Aug-2014) Please run 'e2fsck -f trusty-server-cloudimg-amd64.img' first. $ cp trusty-server-cloudimg-amd64.img trusty-server-cloudimg-amd64.img.dist $ e2fsck -f trusty-server-cloudimg-amd64.img e2fsck 1.42.12 (29-Aug-2014) Pass 1: Checking inodes, blocks, and sizes Pass 2: Checking directory structure Pass 3: Checking directory connectivity Pass 4: Checking reference counts Pass 5: Checking group summary information cloudimg-rootfs: 57885/90112 files (0.0% non-contiguous), 207837/360448 blocks $ resize2fs -P trusty-server-cloudimg-amd64.img resize2fs 1.42.12 (29-Aug-2014) Estimated minimum size of the filesystem: 236103 $ md5sum trusty-server-cloudimg-amd64.img.dist trusty-server-cloudimg-amd64.img 9fd4790c920aaeb0b503ebd2bf7f383c trusty-server-cloudimg-amd64.img.dist c38a3ca8cba7996c85365e122175d013 trusty-server-cloudimg-amd64.img $ dumpe2fs trusty-server-cloudimg-amd64.img | pastebinit dumpe2fs 1.42.12 (29-Aug-2014) http://paste.ubuntu.com/9898831/ $ dumpe2fs trusty-server-cloudimg-amd64.img.dist | pastebinit dumpe2fs 1.42.12 (29-Aug-2014) http://paste.ubuntu.com/9898832/ ## maas images image ## output below is for the maas build process output image ## This one specifically is an arm64 image, and the operations ## done (apt-get update) and such were done with the help chroot via ## qemu-static. ## build the image (works on trusty, fails due to resizing issues on utopic) $ time maas-cloudimg2eph2 -vv --kernel=linux-generic --arch=arm64 \ http://cloud-images.ubuntu.com/daily/server/vivid/20150125/vivid-server-cloudimg-arm64.tar.gz \ /tmp/maas_final/vivid/arm64/20150125/root-image.gz \ --krd-pack=linux-generic,/tmp/maas_final/vivid/arm64/20150125/vivid/generic/boot-kernel,/tmp/maas_final/vivid/arm64/20150125/vivid/generic/boot-initrd 2>&1 | tee out.log $ pastebinit out.log http://paste.ubuntu.com/9899165/ $ zcat /tmp/maas_final/vivid/arm64/20150125/root-image.gz > /tmp/root- image $ ls -l /tmp/root-image -rw-rw-r-- 1 ubuntu ubuntu 1468006400 Jan 27 14:56 /tmp/root-image ## see attached root-image.e2image.xz $ e2image /tmp/root-image /tmp/root-image.e2image e2image 1.42.9 (4-Feb-2014) $ xz /tmp/root-image.e2image ## Now, the above 'root-image' file on utopic, vivid and trusty. ## ## Trusty $ resize2fs -P /tmp/root-image resize2fs 1.42.9 (4-Feb-2014) Estimated minimum size of the filesystem: 274500 $ mkdir -p /tmp/mp && sudo mount -o loop,ro /tmp/root-image /tmp/mp && df /tmp/mp && sudo umount /tmp/mp Filesystem 1K-blocks Used Available Use% Mounted on /dev/loop0 1356344 980284 359676 74% /tmp/mp $ dumpe2fs /tmp/root-image | pastebinit dumpe2fs 1.42.9 (4-Feb-2014) http://paste.ubuntu.com/9899267/ ## Utopic $ resize2fs -P /tmp/root-image resize2fs 1.42.10 (18-May-2014) Estimated minimum size of the filesystem: 358400 $ mkdir -p /tmp/mp && sudo mount -o loop,ro /tmp/root-image /tmp/mp && df /tmp/mp && sudo umount /tmp/mp Filesystem 1K-blocks Used Available Use% Mounted on /dev/loop0 1356344 980284 359676 74% /tmp/mp $ dumpe2fs /tmp/root-image | pastebinit dumpe2fs 1.42.10 (18-May-2014) http://paste.ubuntu.com/9899313/ ## Vivid $ resize2fs -P /tmp/root-image resize2fs 1.42.12 (29-Aug-2014) Estimated minimum size of the filesystem: 358400 $ mkdir -p /tmp/mp && sudo mount -o loop,ro /tmp/root-image /tmp/mp && df /tmp/mp && sudo umount /tmp/mp Filesystem 1K-blocks Used Available Use% Mounted on /dev/loop0 1356344 980284 359676 74% /tmp/mp $ dumpe2fs /tmp/root-image | pastebinit dumpe2fs 1.42.12 (29-Aug-2014) http://paste.ubuntu.com/9899328/ ProblemType: Bug DistroRelease: Ubuntu 15.04 Package: e2fsprogs 1.42.12-1ubuntu1 ProcVersionSignature: User Name 3.18.0-9.10-generic 3.18.2 Uname: Linux 3.18.0-9-generic x86_64 ApportVersion: 2.15.1-0ubuntu2 Architecture: amd64 Date: Tue Jan 27 14:13:26 2015 Ec2AMI: ami-000000f5 Ec2AMIManifest: FIXME Ec2AvailabilityZone: nova Ec2InstanceType: m1.small Ec2Kernel: aki-00000002 Ec2Ramdisk: ari-00000002 ProcEnviron: TERM=xterm PATH=(custom, no user) XDG_RUNTIME_DIR=<set> LANG=en_US.UTF-8 SHELL=/bin/bash SourcePackage: e2fsprogs UpgradeStatus: No upgrade log present (probably fresh install) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/e2fsprogs/+bug/1415077/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp