quota: cleanup dquota sync functions (version 4)

Currently the VFS calls vfs_dq_sync to sync out disk quotas for a given
superblock.  This is a small wrapper around sync_dquots which for the
case of a non-NULL superblock is a small wrapper around quota_sync_sb.

Just make quota_sync_sb global (rename it to sync_quota_sb) and call it
directly.  Also call it directly for those cases in quota.c that have a
superblock and leave sync_dquots purely an iterator over sync_quota_sb and
remove it's superblock argument.

To make this nicer move the check for the lack of a quota_sync method
from the callers into sync_quota_sb.

[folded build fix from Alexander Beregalov <[email protected]>]

Signed-off-by: Christoph Hellwig <[email protected]>
Signed-off-by: Jan Kara <[email protected]>
Signed-off-by: Al Viro <[email protected]>
3 files changed