From: Theodore Ts'o tytso@mit.edu
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@kernel.org Link: https://lore.kernel.org/r/ZIauBR7YiV3rVAHL@glitch Reported-by: Sean Greenslade sean@seangreenslade.com Signed-off-by: Theodore Ts'o tytso@mit.edu Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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;