btrfs: make sure SB_I_VERSION doesn't get unset by remount
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Message ID 20200730151809.4889-1-josef@toxicpanda.com
State New
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Series
  • btrfs: make sure SB_I_VERSION doesn't get unset by remount
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Commit Message

Josef Bacik July 30, 2020, 3:18 p.m. UTC
There's some inconsistency around SB_I_VERSION handling with mount and
remount.  Since we don't really want it to be off ever just work around
this by making sure we don't get the flag cleared on remount.

Reported-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/super.c | 6 ++++++
 1 file changed, 6 insertions(+)

Comments

David Sterba July 30, 2020, 4:32 p.m. UTC | #1
On Thu, Jul 30, 2020 at 11:18:09AM -0400, Josef Bacik wrote:
> There's some inconsistency around SB_I_VERSION handling with mount and
> remount.  Since we don't really want it to be off ever just work around
> this by making sure we don't get the flag cleared on remount.

Agreed. There's a tiny cpu cost of setting the bit, otherwise all
changes to i_version also change some of the times (ctime/mtime) so the
inode needs to be synced. We wouldn't save anything by disabling it.

Patch
diff mbox series

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 5bcdad3ee258..0a9d8b7664f7 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1960,6 +1960,12 @@  static int btrfs_remount(struct super_block *sb, int *flags, char *data)
 		set_bit(BTRFS_FS_OPEN, &fs_info->flags);
 	}
 out:
+	/*
+	 * We need to set S_I_VERSION here otherwise it'll get cleared by VFS,
+	 * since the absence of the flag means it can be toggled off by remount.
+	 */
+	*flags |= SB_I_VERSION;
+
 	wake_up_process(fs_info->transaction_kthread);
 	btrfs_remount_cleanup(fs_info, old_opts);
 	clear_bit(BTRFS_FS_STATE_REMOUNTING, &fs_info->fs_state);