On Mon, Jun 12, 2023 at 01:20:47PM +0700, Bagas Sanjaya wrote: > On Sun, Jun 11, 2023 at 10:32:53PM -0700, Sean Greenslade wrote: > > Hello, folks. > > > > I noticed a change in behavior of ext4 in recent kernels. I make use of > > several luks loopback images formatted as ext4 that I mount read-only > > most of the time. I use rsync to synchronize the backing images between > > machines. In the past, mouning the images as read-only would not touch > > the backing image contents at all, but recently this changed. Every > > mount, even ones that are RO from the start, will cause some small > > writes to the backing image and thus force rsync to scan the whole file. > > > > I confirmed that the issue is still present on v6.4.rc6, so I performed > > a bisect and landed on the following commit: > > > > > eee00237fa5ec8f704f7323b54e48cc34e2d9168 is the first bad commit > > > commit eee00237fa5ec8f704f7323b54e48cc34e2d9168 > > > Author: Ye Bin <yebin10@xxxxxxxxxx> > > > Date: Tue Mar 7 14:17:02 2023 +0800 > > > > > > ext4: commit super block if fs record error when journal record without error > > > > That certainly looks like a likely cause of my issue, but I'm not > > familiar enough with the ext4 code to diagnose any further. Please let > > me know if you need any additional information, or if you would like me > > to test anything. > > > > Can you show dmesg when regression happens? > > Ye: It looks like this regression is caused by your commit. Would you like > to take a look on it? > > Anyway, thanks for the bug report. I'm adding it to regzbot: > > #regzbot ^introduced: eee00237fa5ec8 > #regzbot title: commit super block writes even in read-only filesystems I did a fresh boot on the 6.4 rc6 kernel and did an RO mount and unmount. Here's the full dmesg output from that: [ 48.955896] loop0: detected capacity change from 0 to 4194304 [ 48.965526] Key type trusted registered [ 48.973640] Key type encrypted registered [ 49.032404] EXT4-fs (dm-0): mounted filesystem 4e824972-4523-407e-b0da-3229a71b68d8 ro with ordered data mode. Quota mode: none. [ 61.180755] EXT4-fs (dm-0): unmounting filesystem 4e824972-4523-407e-b0da-3229a71b68d8. [ 61.236958] dm-0: detected capacity change from 4190208 to 0 Thanks, --Sean
