On 10/16/19 4:42 AM, Jan Kara wrote: > On Tue 15-10-19 21:36:08, Eric Sandeen wrote: >> On 10/15/19 2:37 AM, Jan Kara wrote: >>> On Mon 14-10-19 16:30:24, Eric Sandeen wrote: >>>> Anything that walks all inodes on sb->s_inodes list without rescheduling >>>> risks softlockups. >>>> >>>> Previous efforts were made in 2 functions, see: >>>> >>>> c27d82f fs/drop_caches.c: avoid softlockups in drop_pagecache_sb() >>>> ac05fbb inode: don't softlockup when evicting inodes >>>> >>>> but there hasn't been an audit of all walkers, so do that now. This >>>> also consistently moves the cond_resched() calls to the bottom of each >>>> loop in cases where it already exists. >>>> >>>> One loop remains: remove_dquot_ref(), because I'm not quite sure how >>>> to deal with that one w/o taking the i_lock. >>>> >>>> Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx> >>> >>> Thanks Eric. The patch looks good to me. You can add: >>> >>> Reviewed-by: Jan Kara <jack@xxxxxxx> >> >> thanks >> >>> BTW, I suppose you need to add Al to pickup the patch? >> >> Yeah (cc'd now) >> >> But it was just pointed out to me that if/when the majority of inodes >> at umount time have i_count == 0, we'll never hit the resched in >> fsnotify_unmount_inodes() and may still have an issue ... > > Yeah, that's a good point. So that loop will need some further tweaking > (like doing iget-iput dance in need_resched() case like in some other > places). Well, it's already got an iget/iput for anything with i_count > 0. But as the comment says (and I think it's right...) doing an iget/iput on i_count == 0 inodes at this point would be without SB_ACTIVE and the final iput here would actually start evicting inodes in /this/ loop, right? I think we could (ab)use the lru list to construct a "dispose" list for fsnotify processing as was done in evict_inodes... or maybe the two should be merged, and fsnotify watches could be handled directly in evict_inodes. But that doesn't feel quite right. -Eric
