This is a note to let you know that I've just added the patch titled
ext4: avoid updating the superblock on a r/o mount if not needed
to the 6.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
ext4-avoid-updating-the-superblock-on-a-r-o-mount-if-not-needed.patch
and it can be found in the queue-6.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 2ef6c32a914b85217b44a0a2418e830e520b085e Mon Sep 17 00:00:00 2001
From: Theodore Ts'o <tytso@xxxxxxx>
Date: Fri, 23 Jun 2023 10:18:51 -0400
Subject: ext4: avoid updating the superblock on a r/o mount if not needed
From: Theodore Ts'o <tytso@xxxxxxx>
commit 2ef6c32a914b85217b44a0a2418e830e520b085e upstream.
This was noticed by a user who noticied that the mtime of a file
backing a loopback device was getting bumped when the loopback device
is mounted read/only. Note: This doesn't show up when doing a
loopback mount of a file directly, via "mount -o ro /tmp/foo.img
/mnt", since the loop device is set read-only when mount automatically
creates loop device. However, this is noticeable for a LUKS loop
device like this:
% cryptsetup luksOpen /tmp/foo.img test
% mount -o ro /dev/loop0 /mnt ; umount /mnt
or, if LUKS is not in use, if the user manually creates the loop
device like this:
% losetup /dev/loop0 /tmp/foo.img
% mount -o ro /dev/loop0 /mnt ; umount /mnt
The modified mtime causes rsync to do a rolling checksum scan of the
file on the local and remote side, incrementally increasing the time
to rsync the not-modified-but-touched image file.
Fixes: eee00237fa5e ("ext4: commit super block if fs record error when journal record without error")
Cc: stable@xxxxxxxxxx
Link: https://lore.kernel.org/r/ZIauBR7YiV3rVAHL@glitch
Reported-by: Sean Greenslade <sean@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/ext4/super.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -5980,19 +5980,27 @@ static int ext4_load_journal(struct supe
err = jbd2_journal_wipe(journal, !really_read_only);
if (!err) {
char *save = kmalloc(EXT4_S_ERR_LEN, GFP_KERNEL);
+ __le16 orig_state;
+ bool changed = false;
if (save)
memcpy(save, ((char *) es) +
EXT4_S_ERR_START, EXT4_S_ERR_LEN);
err = jbd2_journal_load(journal);
- if (save)
+ if (save && memcmp(((char *) es) + EXT4_S_ERR_START,
+ save, EXT4_S_ERR_LEN)) {
memcpy(((char *) es) + EXT4_S_ERR_START,
save, EXT4_S_ERR_LEN);
+ changed = true;
+ }
kfree(save);
+ orig_state = es->s_state;
es->s_state |= cpu_to_le16(EXT4_SB(sb)->s_mount_state &
EXT4_ERROR_FS);
+ if (orig_state != es->s_state)
+ changed = true;
/* Write out restored error information to the superblock */
- if (!bdev_read_only(sb->s_bdev)) {
+ if (changed && !really_read_only) {
int err2;
err2 = ext4_commit_super(sb);
err = err ? : err2;
Patches currently in stable-queue which might be from tytso@xxxxxxx are
queue-6.4/ext4-turn-quotas-off-if-mount-failed-after-enabling-quotas.patch
queue-6.4/ext4-fix-wrong-unit-use-in-ext4_mb_new_blocks.patch
queue-6.4/ext4-fix-reusing-stale-buffer-heads-from-last-failed-mounting.patch
queue-6.4/ext4-avoid-updating-the-superblock-on-a-r-o-mount-if-not-needed.patch
queue-6.4/ext4-fix-wrong-unit-use-in-ext4_mb_clear_bb.patch
queue-6.4/ext4-get-block-from-bh-in-ext4_free_blocks-for-fast-commit-replay.patch
queue-6.4/ext4-only-update-i_reserved_data_blocks-on-successful-block-allocation.patch
queue-6.4/ext4-fix-to-check-return-value-of-freeze_bdev-in-ext4_shutdown.patch
