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Date: Tue, 06 Jun 2023 14:47:29 +0000
From: bugzilla-daemon@...nel.org
To: linux-ext4@...r.kernel.org
Subject: [Bug 217529] New: Remounting ext4 filesystem from ro to rw fails
when quotas are enabled
https://bugzilla.kernel.org/show_bug.cgi?id=217529
Bug ID: 217529
Summary: Remounting ext4 filesystem from ro to rw fails when
quotas are enabled
Product: File System
Version: 2.5
Hardware: All
OS: Linux
Status: NEW
Severity: normal
Priority: P3
Component: ext4
Assignee: fs_ext4@...nel-bugs.osdl.org
Reporter: nikolas.kraetzschmar@....com
Regression: No
Description
Since commit a44be64, remounting a read-only ext4 filesystem to become
read-write fails when quotas are enabled. The mount syscall returns -EROFS and
outputs the following in dmesg:
```
EXT4-fs warning (device loop0): ext4_enable_quotas:7028: Failed to enable quota
tracking (type=0, err=-30, ino=3). Please run e2fsck
```
Root cause
The problem can be traced back to the changes introduced in commit a44be64. It
appears that the issue arises because the SB_RDONLY bit of the s_flags field is
now only cleared after executing the ext4_enable_quotas function. However, the
vfs_setup_quota_inode function, called by ext4_enable_quotas, checks whether
this bit is set (fs/quota/dquot.c:2331):
```
if (IS_RDONLY(inode))
return -EROFS;
```
This condition therefore always triggers the -EROFS fail condition.
Steps to Reproduce
The bug can be reproduced by executing the following script on a current
mainline kernel with defconfig:
```
#!/bin/bash
set -ex
truncate -s 1G /tmp/img
mkfs.ext4 /tmp/img
tune2fs -Q usrquota,grpquota,prjquota /tmp/img
losetup /dev/loop0 /tmp/img
mount -o ro /dev/loop0 /mnt
mount -o remount,rw /mnt
```
Executing the script results in the following output:
```
+ truncate -s 1G /tmp/img
+ mkfs.ext4 /tmp/img
mke2fs 1.47.0 (5-Feb-2023)
Discarding device blocks: done
Creating filesystem with 262144 4k blocks and 65536 inodes
Filesystem UUID: b96a3da2-043f-11ee-b6f0-47c69db05231
Superblock backups stored on blocks:
32768, 98304, 163840, 229376
Allocating group tables: done
Writing inode tables: done
Creating journal (8192 blocks): done
Writing superblocks and filesystem accounting information: done
+ tune2fs -Q usrquota,grpquota,prjquota /tmp/img
tune2fs 1.47.0 (5-Feb-2023)
+ losetup /dev/loop0 /tmp/img
[ 6.766763] loop0: detected capacity change from 0 to 2097152
+ mount -o ro /dev/loop0 /mnt
[ 6.791561] EXT4-fs (loop0): mounted filesystem
b96a3da2-043f-11ee-b6f0-47c69db05231 ro with ordered data mode. Quota mode:
journalled.
+ mount -o remount,rw /mnt
[ 6.805546] EXT4-fs warning (device loop0): ext4_enable_quotas:7028: Failed
to enable quota tracking (type=0, err=-30, ino=3). Please run e2fsck to fix.
mount: /mnt: cannot remount /dev/loop0 read-write, is write-protected.
dmesg(1) may have more information after failed mount system call.
```
--
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