Tested bionic 4.15.0-152-generic, test passes fine. PASSED. -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1933074
Title: large_dir in ext4 broken Status in linux package in Ubuntu: Triaged Status in linux source package in Bionic: Fix Committed Status in linux source package in Focal: Fix Committed Status in linux source package in Groovy: Fix Committed Status in linux source package in Hirsute: Fix Committed Status in linux source package in Impish: Triaged Bug description: == SRU, Bionic, Focal, Groovy, Hirsute, Impish == [Impact] Creating millions of files on ext4 partition with large_dir support by touching them will eventually trip an ext4 leaf node issue in the index hash. This occurs more frequently when also using smaller block sizes and ends up either with a EXIST or EUCLEAN failure. This occurs on the restart condition when performing do_split. [ Fix ] The fix protects do_split() from the restart condition, making it safe from both current and future ordering of goto statements in earlier sections of the code. The fix is from a patch sent upstream and cc'd to Ted Tso but didn't appear on the ext4 mailing list presumably because it got marked as SPAM. [ Test Case ] Without the fix touching tens of thousands of empty files will trip the issue. It seems to occur more frequently with memory pressure and smaller block sizes, e.g.: sudo mkdir -p /mnt/tmpfs /mnt/storage sudo mount -t tmpfs -o size=9000M tmpfs /mnt/tmpfs sudo dd if=/dev/urandom of=/mnt/tmpfs/ext4.img bs=1M sudo mkfs.ext4 -O large_dir -N 21000000 -O dir_index /mnt/tmpfs/ext4.img -b 1024 -F sudo mount /mnt/tmpfs/ext4.img /mnt/storage and compile and run the attached C program (see https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1933074/+attachment/5509402/+files/touch.c) that quickly populates /mnt/storage with empty files. Without the fix this will terminate with an -EEXIST or -EUCLEAN error on the file creation after several tens of thousands of files. [Where problems could occur] This changes the behaviour of the directory indexing hashing so there is a regression potential that this may introduce subsequent index hashing issues when needed (or not) to do a split. This patch seems to cover all the necessary cases, so I believe this risk is relatively low. I have also tested this on all the kernel series in the SRU with 21,000,000 files so I am confident we have enough test coverage to show the fix is OK. ---------------------------------------------------------- I believe, I found a bug in ext4 in recent kernel versions. I stumbled across this while I was trying to restore a backup to a new VM. How to reproduce this bug: 1. Use a virtual/physical machine with "Ubuntu 18.04.5 LTS" and kernel version 4.15.0-144-generic. 2. add a secondary disk to hold the test files. 3. prepare and mount the filesystem with enabled 'large_dir' flag: mkfs.ext4 -m0 /dev/sdb1; tune2fs -O large_dir /dev/sdb1; mkdir /mnt/storage; mount /dev/sdb1 /mnt/storage; 4. change to directory and create approx. 16 mio files cd /mnt/storage; i=0; while (( $i < 20000000 )); do i=$(( $i + 1 )); (( $i % 1000 == 0 )) && echo $i; touch file_$i.dat || break; done Expected behaviour: - 20 mio files shoud be created without error What happened instead: - The loop aborts with an error message: # 16263100 # touch: cannot touch 'file_16263173.dat': Structure needs cleaning - dmesg gives a little more details: # [Mon Jun 21 03:15:18 2021] EXT4-fs error (device sdb): dx_probe:855: inode #2: block 146221: comm touch: directory leaf block found instead of index block Additional notes: - This occurs on kernel version 4.15.0-144-generic - Not sure, but I believe one test was run on 4.15.0-143-generic and failed too. - Did not check against 4.15.0-142-generic - On 4.15.0-141-generic, the problem does not exist. Behaviour is as expected. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1933074/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
