| Message ID | a26fae1d-a741-6eb1-b460-968a3b97e238@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [V2] fs: avoid softlockups in s_inodes iterators | expand |
On 10/14/19 4:30 PM, 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@redhat.com> Whoops, cc: Jan & Josef as on original, sorry.
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@redhat.com> Thanks Eric. The patch looks good to me. You can add: Reviewed-by: Jan Kara <jack@suse.cz> BTW, I suppose you need to add Al to pickup the patch? Honza > --- > > V2: Drop unrelated iput cleanups in fsnotify > > diff --git a/fs/drop_caches.c b/fs/drop_caches.c > index d31b6c72b476..dc1a1d5d825b 100644 > --- a/fs/drop_caches.c > +++ b/fs/drop_caches.c > @@ -35,11 +35,11 @@ static void drop_pagecache_sb(struct super_block *sb, void *unused) > spin_unlock(&inode->i_lock); > spin_unlock(&sb->s_inode_list_lock); > - cond_resched(); > invalidate_mapping_pages(inode->i_mapping, 0, -1); > iput(toput_inode); > toput_inode = inode; > + cond_resched(); > spin_lock(&sb->s_inode_list_lock); > } > spin_unlock(&sb->s_inode_list_lock); > diff --git a/fs/inode.c b/fs/inode.c > index fef457a42882..b0c789bb3dba 100644 > --- a/fs/inode.c > +++ b/fs/inode.c > @@ -676,6 +676,7 @@ int invalidate_inodes(struct super_block *sb, bool kill_dirty) > struct inode *inode, *next; > LIST_HEAD(dispose); > +again: > spin_lock(&sb->s_inode_list_lock); > list_for_each_entry_safe(inode, next, &sb->s_inodes, i_sb_list) { > spin_lock(&inode->i_lock); > @@ -698,6 +699,13 @@ int invalidate_inodes(struct super_block *sb, bool kill_dirty) > inode_lru_list_del(inode); > spin_unlock(&inode->i_lock); > list_add(&inode->i_lru, &dispose); > + > + if (need_resched()) { > + spin_unlock(&sb->s_inode_list_lock); > + cond_resched(); > + dispose_list(&dispose); > + goto again; > + } > } > spin_unlock(&sb->s_inode_list_lock); > diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c > index 2ecef6155fc0..ac9eb273e28c 100644 > --- a/fs/notify/fsnotify.c > +++ b/fs/notify/fsnotify.c > @@ -77,6 +77,7 @@ static void fsnotify_unmount_inodes(struct super_block *sb) > iput_inode = inode; > + cond_resched(); > spin_lock(&sb->s_inode_list_lock); > } > spin_unlock(&sb->s_inode_list_lock); > diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c > index 6e826b454082..4a085b3c7cac 100644 > --- a/fs/quota/dquot.c > +++ b/fs/quota/dquot.c > @@ -985,6 +985,7 @@ static int add_dquot_ref(struct super_block *sb, int type) > * later. > */ > old_inode = inode; > + cond_resched(); > spin_lock(&sb->s_inode_list_lock); > } > spin_unlock(&sb->s_inode_list_lock); >
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@redhat.com> > > Thanks Eric. The patch looks good to me. You can add: > > Reviewed-by: Jan Kara <jack@suse.cz> 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 ... -Eric
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@redhat.com> > > > > Thanks Eric. The patch looks good to me. You can add: > > > > Reviewed-by: Jan Kara <jack@suse.cz> > > 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). Honza
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@redhat.com> >>> >>> Thanks Eric. The patch looks good to me. You can add: >>> >>> Reviewed-by: Jan Kara <jack@suse.cz> >> >> 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
On Wed 16-10-19 08:23:51, Eric Sandeen wrote: > 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@redhat.com> > >>> > >>> Thanks Eric. The patch looks good to me. You can add: > >>> > >>> Reviewed-by: Jan Kara <jack@suse.cz> > >> > >> 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? Yes, it would but since this is just before calling evict_inodes(), I have currently hard time remembering why evicting inodes like that would be an issue. > 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. Merging the two would be possible (and faster!) as well but I agree it feels a bit dirty :) Honza
On 10/16/19 8:49 AM, Jan Kara wrote: > On Wed 16-10-19 08:23:51, Eric Sandeen wrote: >> 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@redhat.com> >>>>> >>>>> Thanks Eric. The patch looks good to me. You can add: >>>>> >>>>> Reviewed-by: Jan Kara <jack@suse.cz> >>>> >>>> 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? > > Yes, it would but since this is just before calling evict_inodes(), I have > currently hard time remembering why evicting inodes like that would be an > issue. Probably just weird to effectively evict all inodes prior to evict_inodes() ;) >> I think we could (ab)use the lru list to construct a "dispose" list for >> fsnotify processing as was done in evict_inodes... [narrator: Eric's idea here is dumb and it won't work] >> or maybe the two should be merged, and fsnotify watches could be handled >> directly in evict_inodes. But that doesn't feel quite right. > > Merging the two would be possible (and faster!) as well but I agree it > feels a bit dirty :) It's starting to look like maybe the only option... I'll see if Al is willing to merge this patch as is for the simple "schedule the big loops" and see about a 2nd patch on top to do more surgery for this case. Thanks, -Eric > Honza >
On 10/16/19 9:39 AM, Eric Sandeen wrote: > On 10/16/19 8:49 AM, Jan Kara wrote: >> On Wed 16-10-19 08:23:51, Eric Sandeen wrote: >>> 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@redhat.com> >>>>>> >>>>>> Thanks Eric. The patch looks good to me. You can add: >>>>>> >>>>>> Reviewed-by: Jan Kara <jack@suse.cz> >>>>> >>>>> 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? >> >> Yes, it would but since this is just before calling evict_inodes(), I have >> currently hard time remembering why evicting inodes like that would be an >> issue. > > Probably just weird to effectively evict all inodes prior to evict_inodes() ;) > >>> I think we could (ab)use the lru list to construct a "dispose" list for >>> fsnotify processing as was done in evict_inodes... > > [narrator: Eric's idea here is dumb and it won't work] > >>> or maybe the two should be merged, and fsnotify watches could be handled >>> directly in evict_inodes. But that doesn't feel quite right. >> >> Merging the two would be possible (and faster!) as well but I agree it >> feels a bit dirty :) > > It's starting to look like maybe the only option... > > I'll see if Al is willing to merge this patch as is for the simple "schedule > the big loops" and see about a 2nd patch on top to do more surgery for this > case. Sorry for thinking out loud in public but I'm not too familiar with fsnotify, so I'm being timid. However, since fsnotify_sb_delete() and evict_inodes() are working on orthogonal sets of inodes (fsnotify_sb_delete only cares about nonzero refcount, and evict_inodes only cares about zero refcount), I think we can just swap the order of the calls. The fsnotify call will then have a much smaller list to walk (any refcounted inodes) as well. I'll try to give this a test. diff --git a/fs/super.c b/fs/super.c index cfadab2cbf35..cd352530eca9 100644 --- a/fs/super.c +++ b/fs/super.c @@ -448,10 +448,12 @@ void generic_shutdown_super(struct super_block *sb) sync_filesystem(sb); sb->s_flags &= ~SB_ACTIVE; - fsnotify_sb_delete(sb); cgroup_writeback_umount(); + /* evict all inodes with zero refcount */ evict_inodes(sb); + /* only nonzero refcount inodes can have marks */ + fsnotify_sb_delete(sb); if (sb->s_dio_done_wq) { destroy_workqueue(sb->s_dio_done_wq);
On Wed 16-10-19 10:26:16, Eric Sandeen wrote: > On 10/16/19 9:39 AM, Eric Sandeen wrote: > > On 10/16/19 8:49 AM, Jan Kara wrote: > >> On Wed 16-10-19 08:23:51, Eric Sandeen wrote: > >>> 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@redhat.com> > >>>>>> > >>>>>> Thanks Eric. The patch looks good to me. You can add: > >>>>>> > >>>>>> Reviewed-by: Jan Kara <jack@suse.cz> > >>>>> > >>>>> 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? > >> > >> Yes, it would but since this is just before calling evict_inodes(), I have > >> currently hard time remembering why evicting inodes like that would be an > >> issue. > > > > Probably just weird to effectively evict all inodes prior to evict_inodes() ;) > > > >>> I think we could (ab)use the lru list to construct a "dispose" list for > >>> fsnotify processing as was done in evict_inodes... > > > > [narrator: Eric's idea here is dumb and it won't work] > > > >>> or maybe the two should be merged, and fsnotify watches could be handled > >>> directly in evict_inodes. But that doesn't feel quite right. > >> > >> Merging the two would be possible (and faster!) as well but I agree it > >> feels a bit dirty :) > > > > It's starting to look like maybe the only option... > > > > I'll see if Al is willing to merge this patch as is for the simple "schedule > > the big loops" and see about a 2nd patch on top to do more surgery for this > > case. > > Sorry for thinking out loud in public but I'm not too familiar with fsnotify, so > I'm being timid. However, since fsnotify_sb_delete() and evict_inodes() are working > on orthogonal sets of inodes (fsnotify_sb_delete only cares about nonzero refcount, > and evict_inodes only cares about zero refcount), I think we can just swap the order > of the calls. The fsnotify call will then have a much smaller list to walk > (any refcounted inodes) as well. > > I'll try to give this a test. Yes, this should make the softlockup impossible to trigger in practice. So agreed. Honza > > diff --git a/fs/super.c b/fs/super.c > index cfadab2cbf35..cd352530eca9 100644 > --- a/fs/super.c > +++ b/fs/super.c > @@ -448,10 +448,12 @@ void generic_shutdown_super(struct super_block *sb) > sync_filesystem(sb); > sb->s_flags &= ~SB_ACTIVE; > > - fsnotify_sb_delete(sb); > cgroup_writeback_umount(); > > + /* evict all inodes with zero refcount */ > evict_inodes(sb); > + /* only nonzero refcount inodes can have marks */ > + fsnotify_sb_delete(sb); > > if (sb->s_dio_done_wq) { > destroy_workqueue(sb->s_dio_done_wq); > >
diff --git a/fs/drop_caches.c b/fs/drop_caches.c index d31b6c72b476..dc1a1d5d825b 100644 --- a/fs/drop_caches.c +++ b/fs/drop_caches.c @@ -35,11 +35,11 @@ static void drop_pagecache_sb(struct super_block *sb, void *unused) spin_unlock(&inode->i_lock); spin_unlock(&sb->s_inode_list_lock); - cond_resched(); invalidate_mapping_pages(inode->i_mapping, 0, -1); iput(toput_inode); toput_inode = inode; + cond_resched(); spin_lock(&sb->s_inode_list_lock); } spin_unlock(&sb->s_inode_list_lock); diff --git a/fs/inode.c b/fs/inode.c index fef457a42882..b0c789bb3dba 100644 --- a/fs/inode.c +++ b/fs/inode.c @@ -676,6 +676,7 @@ int invalidate_inodes(struct super_block *sb, bool kill_dirty) struct inode *inode, *next; LIST_HEAD(dispose); +again: spin_lock(&sb->s_inode_list_lock); list_for_each_entry_safe(inode, next, &sb->s_inodes, i_sb_list) { spin_lock(&inode->i_lock); @@ -698,6 +699,13 @@ int invalidate_inodes(struct super_block *sb, bool kill_dirty) inode_lru_list_del(inode); spin_unlock(&inode->i_lock); list_add(&inode->i_lru, &dispose); + + if (need_resched()) { + spin_unlock(&sb->s_inode_list_lock); + cond_resched(); + dispose_list(&dispose); + goto again; + } } spin_unlock(&sb->s_inode_list_lock); diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c index 2ecef6155fc0..ac9eb273e28c 100644 --- a/fs/notify/fsnotify.c +++ b/fs/notify/fsnotify.c @@ -77,6 +77,7 @@ static void fsnotify_unmount_inodes(struct super_block *sb) iput_inode = inode; + cond_resched(); spin_lock(&sb->s_inode_list_lock); } spin_unlock(&sb->s_inode_list_lock); diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c index 6e826b454082..4a085b3c7cac 100644 --- a/fs/quota/dquot.c +++ b/fs/quota/dquot.c @@ -985,6 +985,7 @@ static int add_dquot_ref(struct super_block *sb, int type) * later. */ old_inode = inode; + cond_resched(); spin_lock(&sb->s_inode_list_lock); } spin_unlock(&sb->s_inode_list_lock);
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@redhat.com> --- V2: Drop unrelated iput cleanups in fsnotify