On Thu 25-07-24 10:39:58, Haifeng Xu wrote: > When deactivating any type of superblock, it had to wait for the in-flight > wb switches to be completed. wb switches are executed in inode_switch_wbs_work_fn() > which needs to acquire the wb_switch_rwsem and races against sync_inodes_sb(). > If there are too much dirty data in the superblock, the waiting time may increase > significantly. > > For superblocks without cgroup writeback such as tmpfs, they have nothing to > do with the wb swithes, so the flushing can be avoided. > > Signed-off-by: Haifeng Xu <haifeng.xu@xxxxxxxxxx> > --- > fs/super.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/fs/super.c b/fs/super.c > index 095ba793e10c..f846f853e957 100644 > --- a/fs/super.c > +++ b/fs/super.c > @@ -621,7 +621,8 @@ void generic_shutdown_super(struct super_block *sb) > sync_filesystem(sb); > sb->s_flags &= ~SB_ACTIVE; > > - cgroup_writeback_umount(); > + if (sb->s_bdi != &noop_backing_dev_info) > + cgroup_writeback_umount(); So a more obvious check would be: if (sb->s_bdi->capabilities & BDI_CAP_WRITEBACK) even better would be if we'd pass 'sb' into cgroup_writeback_umount() and that function would do this check inside so that callers don't have to bother... I know there is only one caller so this is not a huge deal but still I'd find it cleaner that way. Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
