diff options
author | Theodore Ts'o <tytso@mit.edu> | 2023-06-23 17:18:51 +0300 |
---|---|---|
committer | Theodore Ts'o <tytso@mit.edu> | 2023-06-27 02:36:45 +0300 |
commit | 2ef6c32a914b85217b44a0a2418e830e520b085e (patch) | |
tree | 3edb2ad5060e8f3f760b6e15b2188148b685dbf8 /fs | |
parent | 31464ab01fff910cb88376384e2b6824f7bf713f (diff) | |
download | linux-2ef6c32a914b85217b44a0a2418e830e520b085e.tar.xz |
ext4: avoid updating the superblock on a r/o mount if not needed
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>
Diffstat (limited to 'fs')
-rw-r--r-- | fs/ext4/super.c | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/fs/ext4/super.c b/fs/ext4/super.c index b3819e70093e..c638b0db3b2b 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -5997,19 +5997,27 @@ static int ext4_load_journal(struct super_block *sb, 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; |