| Message ID | 20210209174646.1310591-8-shy828301@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v7,01/12] mm: vmscan: use nid from shrink_control for tracepoint | expand |
On Tue, Feb 09, 2021 at 09:46:41AM -0800, Yang Shi wrote: > Currently registered shrinker is indicated by non-NULL shrinker->nr_deferred. > This approach is fine with nr_deferred at the shrinker level, but the following > patches will move MEMCG_AWARE shrinkers' nr_deferred to memcg level, so their > shrinker->nr_deferred would always be NULL. This would prevent the shrinkers > from unregistering correctly. > > Remove SHRINKER_REGISTERING since we could check if shrinker is registered > successfully by the new flag. > > Acked-by: Kirill Tkhai <ktkhai@virtuozzo.com> > Signed-off-by: Yang Shi <shy828301@gmail.com> > --- > include/linux/shrinker.h | 7 ++++--- > mm/vmscan.c | 31 +++++++++---------------------- > 2 files changed, 13 insertions(+), 25 deletions(-) > > diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h > index 0f80123650e2..1eac79ce57d4 100644 > --- a/include/linux/shrinker.h > +++ b/include/linux/shrinker.h > @@ -79,13 +79,14 @@ struct shrinker { > #define DEFAULT_SEEKS 2 /* A good number if you don't know better. */ > > /* Flags */ > -#define SHRINKER_NUMA_AWARE (1 << 0) > -#define SHRINKER_MEMCG_AWARE (1 << 1) > +#define SHRINKER_REGISTERED (1 << 0) > +#define SHRINKER_NUMA_AWARE (1 << 1) > +#define SHRINKER_MEMCG_AWARE (1 << 2) > /* > * It just makes sense when the shrinker is also MEMCG_AWARE for now, > * non-MEMCG_AWARE shrinker should not have this flag set. > */ > -#define SHRINKER_NONSLAB (1 << 2) > +#define SHRINKER_NONSLAB (1 << 3) > > extern int prealloc_shrinker(struct shrinker *shrinker); > extern void register_shrinker_prepared(struct shrinker *shrinker); > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 273efbf4d53c..a047980536cf 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -315,19 +315,6 @@ void set_shrinker_bit(struct mem_cgroup *memcg, int nid, int shrinker_id) > } > } > > -/* > - * We allow subsystems to populate their shrinker-related > - * LRU lists before register_shrinker_prepared() is called > - * for the shrinker, since we don't want to impose > - * restrictions on their internal registration order. > - * In this case shrink_slab_memcg() may find corresponding > - * bit is set in the shrinkers map. > - * > - * This value is used by the function to detect registering > - * shrinkers and to skip do_shrink_slab() calls for them. > - */ > -#define SHRINKER_REGISTERING ((struct shrinker *)~0UL) > - > static DEFINE_IDR(shrinker_idr); > > static int prealloc_memcg_shrinker(struct shrinker *shrinker) > @@ -336,7 +323,7 @@ static int prealloc_memcg_shrinker(struct shrinker *shrinker) > > down_write(&shrinker_rwsem); > /* This may call shrinker, so it must use down_read_trylock() */ > - id = idr_alloc(&shrinker_idr, SHRINKER_REGISTERING, 0, 0, GFP_KERNEL); > + id = idr_alloc(&shrinker_idr, shrinker, 0, 0, GFP_KERNEL); > if (id < 0) > goto unlock; > > @@ -499,10 +486,7 @@ void register_shrinker_prepared(struct shrinker *shrinker) > { > down_write(&shrinker_rwsem); > list_add_tail(&shrinker->list, &shrinker_list); > -#ifdef CONFIG_MEMCG > - if (shrinker->flags & SHRINKER_MEMCG_AWARE) > - idr_replace(&shrinker_idr, shrinker, shrinker->id); > -#endif > + shrinker->flags |= SHRINKER_REGISTERED; > up_write(&shrinker_rwsem); > } > > @@ -522,13 +506,16 @@ EXPORT_SYMBOL(register_shrinker); > */ > void unregister_shrinker(struct shrinker *shrinker) > { > - if (!shrinker->nr_deferred) > + if (!(shrinker->flags & SHRINKER_REGISTERED)) > return; > - if (shrinker->flags & SHRINKER_MEMCG_AWARE) > - unregister_memcg_shrinker(shrinker); > + > down_write(&shrinker_rwsem); > list_del(&shrinker->list); > + shrinker->flags &= ~SHRINKER_REGISTERED; > up_write(&shrinker_rwsem); > + > + if (shrinker->flags & SHRINKER_MEMCG_AWARE) > + unregister_memcg_shrinker(shrinker); Because unregister_memcg_shrinker() will take and release shrinker_rwsem once again, I wonder if it's better to move it into the locked section and change the calling convention to require the caller to take the semaphore? > kfree(shrinkrem->nr_deferred); > shrinker->nr_deferred = NULL; > } > @@ -693,7 +680,7 @@ static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid, > struct shrinker *shrinker; > > shrinker = idr_find(&shrinker_idr, i); > - if (unlikely(!shrinker || shrinker == SHRINKER_REGISTERING)) { > + if (unlikely(!shrinker || !(shrinker->flags & SHRINKER_REGISTERED))) { > if (!shrinker) > clear_bit(i, info->map); > continue; > -- > 2.26.2 >
On Tue, Feb 9, 2021 at 4:39 PM Roman Gushchin <guro@fb.com> wrote: > > On Tue, Feb 09, 2021 at 09:46:41AM -0800, Yang Shi wrote: > > Currently registered shrinker is indicated by non-NULL shrinker->nr_deferred. > > This approach is fine with nr_deferred at the shrinker level, but the following > > patches will move MEMCG_AWARE shrinkers' nr_deferred to memcg level, so their > > shrinker->nr_deferred would always be NULL. This would prevent the shrinkers > > from unregistering correctly. > > > > Remove SHRINKER_REGISTERING since we could check if shrinker is registered > > successfully by the new flag. > > > > Acked-by: Kirill Tkhai <ktkhai@virtuozzo.com> > > Signed-off-by: Yang Shi <shy828301@gmail.com> > > --- > > include/linux/shrinker.h | 7 ++++--- > > mm/vmscan.c | 31 +++++++++---------------------- > > 2 files changed, 13 insertions(+), 25 deletions(-) > > > > diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h > > index 0f80123650e2..1eac79ce57d4 100644 > > --- a/include/linux/shrinker.h > > +++ b/include/linux/shrinker.h > > @@ -79,13 +79,14 @@ struct shrinker { > > #define DEFAULT_SEEKS 2 /* A good number if you don't know better. */ > > > > /* Flags */ > > -#define SHRINKER_NUMA_AWARE (1 << 0) > > -#define SHRINKER_MEMCG_AWARE (1 << 1) > > +#define SHRINKER_REGISTERED (1 << 0) > > +#define SHRINKER_NUMA_AWARE (1 << 1) > > +#define SHRINKER_MEMCG_AWARE (1 << 2) > > /* > > * It just makes sense when the shrinker is also MEMCG_AWARE for now, > > * non-MEMCG_AWARE shrinker should not have this flag set. > > */ > > -#define SHRINKER_NONSLAB (1 << 2) > > +#define SHRINKER_NONSLAB (1 << 3) > > > > extern int prealloc_shrinker(struct shrinker *shrinker); > > extern void register_shrinker_prepared(struct shrinker *shrinker); > > diff --git a/mm/vmscan.c b/mm/vmscan.c > > index 273efbf4d53c..a047980536cf 100644 > > --- a/mm/vmscan.c > > +++ b/mm/vmscan.c > > @@ -315,19 +315,6 @@ void set_shrinker_bit(struct mem_cgroup *memcg, int nid, int shrinker_id) > > } > > } > > > > -/* > > - * We allow subsystems to populate their shrinker-related > > - * LRU lists before register_shrinker_prepared() is called > > - * for the shrinker, since we don't want to impose > > - * restrictions on their internal registration order. > > - * In this case shrink_slab_memcg() may find corresponding > > - * bit is set in the shrinkers map. > > - * > > - * This value is used by the function to detect registering > > - * shrinkers and to skip do_shrink_slab() calls for them. > > - */ > > -#define SHRINKER_REGISTERING ((struct shrinker *)~0UL) > > - > > static DEFINE_IDR(shrinker_idr); > > > > static int prealloc_memcg_shrinker(struct shrinker *shrinker) > > @@ -336,7 +323,7 @@ static int prealloc_memcg_shrinker(struct shrinker *shrinker) > > > > down_write(&shrinker_rwsem); > > /* This may call shrinker, so it must use down_read_trylock() */ > > - id = idr_alloc(&shrinker_idr, SHRINKER_REGISTERING, 0, 0, GFP_KERNEL); > > + id = idr_alloc(&shrinker_idr, shrinker, 0, 0, GFP_KERNEL); > > if (id < 0) > > goto unlock; > > > > @@ -499,10 +486,7 @@ void register_shrinker_prepared(struct shrinker *shrinker) > > { > > down_write(&shrinker_rwsem); > > list_add_tail(&shrinker->list, &shrinker_list); > > -#ifdef CONFIG_MEMCG > > - if (shrinker->flags & SHRINKER_MEMCG_AWARE) > > - idr_replace(&shrinker_idr, shrinker, shrinker->id); > > -#endif > > + shrinker->flags |= SHRINKER_REGISTERED; > > up_write(&shrinker_rwsem); > > } > > > > @@ -522,13 +506,16 @@ EXPORT_SYMBOL(register_shrinker); > > */ > > void unregister_shrinker(struct shrinker *shrinker) > > { > > - if (!shrinker->nr_deferred) > > + if (!(shrinker->flags & SHRINKER_REGISTERED)) > > return; > > - if (shrinker->flags & SHRINKER_MEMCG_AWARE) > > - unregister_memcg_shrinker(shrinker); > > + > > down_write(&shrinker_rwsem); > > list_del(&shrinker->list); > > + shrinker->flags &= ~SHRINKER_REGISTERED; > > up_write(&shrinker_rwsem); > > + > > + if (shrinker->flags & SHRINKER_MEMCG_AWARE) > > + unregister_memcg_shrinker(shrinker); > > Because unregister_memcg_shrinker() will take and release shrinker_rwsem once again, > I wonder if it's better to move it into the locked section and change the calling > convention to require the caller to take the semaphore? I don't think we could do that since unregister_memcg_shrinker() is called by free_prealloced_shrinker() which is called without holding the shrinker_rwsem by fs and workingset code. We could add a bool parameter to indicate if the rwsem was acquired or not, but IMHO it seems not worth it. > > > kfree(shrinkrem->nr_deferred); > > shrinker->nr_deferred = NULL; > > } > > @@ -693,7 +680,7 @@ static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid, > > struct shrinker *shrinker; > > > > shrinker = idr_find(&shrinker_idr, i); > > - if (unlikely(!shrinker || shrinker == SHRINKER_REGISTERING)) { > > + if (unlikely(!shrinker || !(shrinker->flags & SHRINKER_REGISTERED))) { > > if (!shrinker) > > clear_bit(i, info->map); > > continue; > > -- > > 2.26.2 > >
On Tue, Feb 09, 2021 at 05:12:51PM -0800, Yang Shi wrote: > On Tue, Feb 9, 2021 at 4:39 PM Roman Gushchin <guro@fb.com> wrote: > > > > On Tue, Feb 09, 2021 at 09:46:41AM -0800, Yang Shi wrote: > > > Currently registered shrinker is indicated by non-NULL shrinker->nr_deferred. > > > This approach is fine with nr_deferred at the shrinker level, but the following > > > patches will move MEMCG_AWARE shrinkers' nr_deferred to memcg level, so their > > > shrinker->nr_deferred would always be NULL. This would prevent the shrinkers > > > from unregistering correctly. > > > > > > Remove SHRINKER_REGISTERING since we could check if shrinker is registered > > > successfully by the new flag. > > > > > > Acked-by: Kirill Tkhai <ktkhai@virtuozzo.com> > > > Signed-off-by: Yang Shi <shy828301@gmail.com> > > > --- > > > include/linux/shrinker.h | 7 ++++--- > > > mm/vmscan.c | 31 +++++++++---------------------- > > > 2 files changed, 13 insertions(+), 25 deletions(-) > > > > > > diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h > > > index 0f80123650e2..1eac79ce57d4 100644 > > > --- a/include/linux/shrinker.h > > > +++ b/include/linux/shrinker.h > > > @@ -79,13 +79,14 @@ struct shrinker { > > > #define DEFAULT_SEEKS 2 /* A good number if you don't know better. */ > > > > > > /* Flags */ > > > -#define SHRINKER_NUMA_AWARE (1 << 0) > > > -#define SHRINKER_MEMCG_AWARE (1 << 1) > > > +#define SHRINKER_REGISTERED (1 << 0) > > > +#define SHRINKER_NUMA_AWARE (1 << 1) > > > +#define SHRINKER_MEMCG_AWARE (1 << 2) > > > /* > > > * It just makes sense when the shrinker is also MEMCG_AWARE for now, > > > * non-MEMCG_AWARE shrinker should not have this flag set. > > > */ > > > -#define SHRINKER_NONSLAB (1 << 2) > > > +#define SHRINKER_NONSLAB (1 << 3) > > > > > > extern int prealloc_shrinker(struct shrinker *shrinker); > > > extern void register_shrinker_prepared(struct shrinker *shrinker); > > > diff --git a/mm/vmscan.c b/mm/vmscan.c > > > index 273efbf4d53c..a047980536cf 100644 > > > --- a/mm/vmscan.c > > > +++ b/mm/vmscan.c > > > @@ -315,19 +315,6 @@ void set_shrinker_bit(struct mem_cgroup *memcg, int nid, int shrinker_id) > > > } > > > } > > > > > > -/* > > > - * We allow subsystems to populate their shrinker-related > > > - * LRU lists before register_shrinker_prepared() is called > > > - * for the shrinker, since we don't want to impose > > > - * restrictions on their internal registration order. > > > - * In this case shrink_slab_memcg() may find corresponding > > > - * bit is set in the shrinkers map. > > > - * > > > - * This value is used by the function to detect registering > > > - * shrinkers and to skip do_shrink_slab() calls for them. > > > - */ > > > -#define SHRINKER_REGISTERING ((struct shrinker *)~0UL) > > > - > > > static DEFINE_IDR(shrinker_idr); > > > > > > static int prealloc_memcg_shrinker(struct shrinker *shrinker) > > > @@ -336,7 +323,7 @@ static int prealloc_memcg_shrinker(struct shrinker *shrinker) > > > > > > down_write(&shrinker_rwsem); > > > /* This may call shrinker, so it must use down_read_trylock() */ > > > - id = idr_alloc(&shrinker_idr, SHRINKER_REGISTERING, 0, 0, GFP_KERNEL); > > > + id = idr_alloc(&shrinker_idr, shrinker, 0, 0, GFP_KERNEL); > > > if (id < 0) > > > goto unlock; > > > > > > @@ -499,10 +486,7 @@ void register_shrinker_prepared(struct shrinker *shrinker) > > > { > > > down_write(&shrinker_rwsem); > > > list_add_tail(&shrinker->list, &shrinker_list); > > > -#ifdef CONFIG_MEMCG > > > - if (shrinker->flags & SHRINKER_MEMCG_AWARE) > > > - idr_replace(&shrinker_idr, shrinker, shrinker->id); > > > -#endif > > > + shrinker->flags |= SHRINKER_REGISTERED; > > > up_write(&shrinker_rwsem); > > > } > > > > > > @@ -522,13 +506,16 @@ EXPORT_SYMBOL(register_shrinker); > > > */ > > > void unregister_shrinker(struct shrinker *shrinker) > > > { > > > - if (!shrinker->nr_deferred) > > > + if (!(shrinker->flags & SHRINKER_REGISTERED)) > > > return; > > > - if (shrinker->flags & SHRINKER_MEMCG_AWARE) > > > - unregister_memcg_shrinker(shrinker); > > > + > > > down_write(&shrinker_rwsem); > > > list_del(&shrinker->list); > > > + shrinker->flags &= ~SHRINKER_REGISTERED; > > > up_write(&shrinker_rwsem); > > > + > > > + if (shrinker->flags & SHRINKER_MEMCG_AWARE) > > > + unregister_memcg_shrinker(shrinker); > > > > Because unregister_memcg_shrinker() will take and release shrinker_rwsem once again, > > I wonder if it's better to move it into the locked section and change the calling > > convention to require the caller to take the semaphore? > > I don't think we could do that since unregister_memcg_shrinker() is > called by free_prealloced_shrinker() which is called without holding > the shrinker_rwsem by fs and workingset code. > > We could add a bool parameter to indicate if the rwsem was acquired or > not, but IMHO it seems not worth it. Can free_preallocated_shrinker() just do if (shrinker->flags & SHRINKER_MEMCG_AWARE) { down_write(&shrinker_rwsem); unregister_memcg_shrinker(shrinker); up_write(&shrinker_rwsem); } ?
On Tue, Feb 9, 2021 at 5:34 PM Roman Gushchin <guro@fb.com> wrote: > > On Tue, Feb 09, 2021 at 05:12:51PM -0800, Yang Shi wrote: > > On Tue, Feb 9, 2021 at 4:39 PM Roman Gushchin <guro@fb.com> wrote: > > > > > > On Tue, Feb 09, 2021 at 09:46:41AM -0800, Yang Shi wrote: > > > > Currently registered shrinker is indicated by non-NULL shrinker->nr_deferred. > > > > This approach is fine with nr_deferred at the shrinker level, but the following > > > > patches will move MEMCG_AWARE shrinkers' nr_deferred to memcg level, so their > > > > shrinker->nr_deferred would always be NULL. This would prevent the shrinkers > > > > from unregistering correctly. > > > > > > > > Remove SHRINKER_REGISTERING since we could check if shrinker is registered > > > > successfully by the new flag. > > > > > > > > Acked-by: Kirill Tkhai <ktkhai@virtuozzo.com> > > > > Signed-off-by: Yang Shi <shy828301@gmail.com> > > > > --- > > > > include/linux/shrinker.h | 7 ++++--- > > > > mm/vmscan.c | 31 +++++++++---------------------- > > > > 2 files changed, 13 insertions(+), 25 deletions(-) > > > > > > > > diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h > > > > index 0f80123650e2..1eac79ce57d4 100644 > > > > --- a/include/linux/shrinker.h > > > > +++ b/include/linux/shrinker.h > > > > @@ -79,13 +79,14 @@ struct shrinker { > > > > #define DEFAULT_SEEKS 2 /* A good number if you don't know better. */ > > > > > > > > /* Flags */ > > > > -#define SHRINKER_NUMA_AWARE (1 << 0) > > > > -#define SHRINKER_MEMCG_AWARE (1 << 1) > > > > +#define SHRINKER_REGISTERED (1 << 0) > > > > +#define SHRINKER_NUMA_AWARE (1 << 1) > > > > +#define SHRINKER_MEMCG_AWARE (1 << 2) > > > > /* > > > > * It just makes sense when the shrinker is also MEMCG_AWARE for now, > > > > * non-MEMCG_AWARE shrinker should not have this flag set. > > > > */ > > > > -#define SHRINKER_NONSLAB (1 << 2) > > > > +#define SHRINKER_NONSLAB (1 << 3) > > > > > > > > extern int prealloc_shrinker(struct shrinker *shrinker); > > > > extern void register_shrinker_prepared(struct shrinker *shrinker); > > > > diff --git a/mm/vmscan.c b/mm/vmscan.c > > > > index 273efbf4d53c..a047980536cf 100644 > > > > --- a/mm/vmscan.c > > > > +++ b/mm/vmscan.c > > > > @@ -315,19 +315,6 @@ void set_shrinker_bit(struct mem_cgroup *memcg, int nid, int shrinker_id) > > > > } > > > > } > > > > > > > > -/* > > > > - * We allow subsystems to populate their shrinker-related > > > > - * LRU lists before register_shrinker_prepared() is called > > > > - * for the shrinker, since we don't want to impose > > > > - * restrictions on their internal registration order. > > > > - * In this case shrink_slab_memcg() may find corresponding > > > > - * bit is set in the shrinkers map. > > > > - * > > > > - * This value is used by the function to detect registering > > > > - * shrinkers and to skip do_shrink_slab() calls for them. > > > > - */ > > > > -#define SHRINKER_REGISTERING ((struct shrinker *)~0UL) > > > > - > > > > static DEFINE_IDR(shrinker_idr); > > > > > > > > static int prealloc_memcg_shrinker(struct shrinker *shrinker) > > > > @@ -336,7 +323,7 @@ static int prealloc_memcg_shrinker(struct shrinker *shrinker) > > > > > > > > down_write(&shrinker_rwsem); > > > > /* This may call shrinker, so it must use down_read_trylock() */ > > > > - id = idr_alloc(&shrinker_idr, SHRINKER_REGISTERING, 0, 0, GFP_KERNEL); > > > > + id = idr_alloc(&shrinker_idr, shrinker, 0, 0, GFP_KERNEL); > > > > if (id < 0) > > > > goto unlock; > > > > > > > > @@ -499,10 +486,7 @@ void register_shrinker_prepared(struct shrinker *shrinker) > > > > { > > > > down_write(&shrinker_rwsem); > > > > list_add_tail(&shrinker->list, &shrinker_list); > > > > -#ifdef CONFIG_MEMCG > > > > - if (shrinker->flags & SHRINKER_MEMCG_AWARE) > > > > - idr_replace(&shrinker_idr, shrinker, shrinker->id); > > > > -#endif > > > > + shrinker->flags |= SHRINKER_REGISTERED; > > > > up_write(&shrinker_rwsem); > > > > } > > > > > > > > @@ -522,13 +506,16 @@ EXPORT_SYMBOL(register_shrinker); > > > > */ > > > > void unregister_shrinker(struct shrinker *shrinker) > > > > { > > > > - if (!shrinker->nr_deferred) > > > > + if (!(shrinker->flags & SHRINKER_REGISTERED)) > > > > return; > > > > - if (shrinker->flags & SHRINKER_MEMCG_AWARE) > > > > - unregister_memcg_shrinker(shrinker); > > > > + > > > > down_write(&shrinker_rwsem); > > > > list_del(&shrinker->list); > > > > + shrinker->flags &= ~SHRINKER_REGISTERED; > > > > up_write(&shrinker_rwsem); > > > > + > > > > + if (shrinker->flags & SHRINKER_MEMCG_AWARE) > > > > + unregister_memcg_shrinker(shrinker); > > > > > > Because unregister_memcg_shrinker() will take and release shrinker_rwsem once again, > > > I wonder if it's better to move it into the locked section and change the calling > > > convention to require the caller to take the semaphore? > > > > I don't think we could do that since unregister_memcg_shrinker() is > > called by free_prealloced_shrinker() which is called without holding > > the shrinker_rwsem by fs and workingset code. > > > > We could add a bool parameter to indicate if the rwsem was acquired or > > not, but IMHO it seems not worth it. > > Can free_preallocated_shrinker() just do > > if (shrinker->flags & SHRINKER_MEMCG_AWARE) { > down_write(&shrinker_rwsem); > unregister_memcg_shrinker(shrinker); > up_write(&shrinker_rwsem); > } > > ? Aha, yes. I didn't think of that way.
On 2/9/21 6:46 PM, Yang Shi wrote: > Currently registered shrinker is indicated by non-NULL shrinker->nr_deferred. > This approach is fine with nr_deferred at the shrinker level, but the following > patches will move MEMCG_AWARE shrinkers' nr_deferred to memcg level, so their > shrinker->nr_deferred would always be NULL. This would prevent the shrinkers > from unregistering correctly. > > Remove SHRINKER_REGISTERING since we could check if shrinker is registered > successfully by the new flag. > > Acked-by: Kirill Tkhai <ktkhai@virtuozzo.com> > Signed-off-by: Yang Shi <shy828301@gmail.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> With Roman's suggestion it's fine by me too.
On Tue, Feb 9, 2021 at 4:39 PM Roman Gushchin <guro@fb.com> wrote: > > On Tue, Feb 09, 2021 at 09:46:41AM -0800, Yang Shi wrote: > > Currently registered shrinker is indicated by non-NULL shrinker->nr_deferred. > > This approach is fine with nr_deferred at the shrinker level, but the following > > patches will move MEMCG_AWARE shrinkers' nr_deferred to memcg level, so their > > shrinker->nr_deferred would always be NULL. This would prevent the shrinkers > > from unregistering correctly. > > > > Remove SHRINKER_REGISTERING since we could check if shrinker is registered > > successfully by the new flag. > > > > Acked-by: Kirill Tkhai <ktkhai@virtuozzo.com> > > Signed-off-by: Yang Shi <shy828301@gmail.com> > > --- > > include/linux/shrinker.h | 7 ++++--- > > mm/vmscan.c | 31 +++++++++---------------------- > > 2 files changed, 13 insertions(+), 25 deletions(-) > > > > diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h > > index 0f80123650e2..1eac79ce57d4 100644 > > --- a/include/linux/shrinker.h > > +++ b/include/linux/shrinker.h > > @@ -79,13 +79,14 @@ struct shrinker { > > #define DEFAULT_SEEKS 2 /* A good number if you don't know better. */ > > > > /* Flags */ > > -#define SHRINKER_NUMA_AWARE (1 << 0) > > -#define SHRINKER_MEMCG_AWARE (1 << 1) > > +#define SHRINKER_REGISTERED (1 << 0) > > +#define SHRINKER_NUMA_AWARE (1 << 1) > > +#define SHRINKER_MEMCG_AWARE (1 << 2) > > /* > > * It just makes sense when the shrinker is also MEMCG_AWARE for now, > > * non-MEMCG_AWARE shrinker should not have this flag set. > > */ > > -#define SHRINKER_NONSLAB (1 << 2) > > +#define SHRINKER_NONSLAB (1 << 3) > > > > extern int prealloc_shrinker(struct shrinker *shrinker); > > extern void register_shrinker_prepared(struct shrinker *shrinker); > > diff --git a/mm/vmscan.c b/mm/vmscan.c > > index 273efbf4d53c..a047980536cf 100644 > > --- a/mm/vmscan.c > > +++ b/mm/vmscan.c > > @@ -315,19 +315,6 @@ void set_shrinker_bit(struct mem_cgroup *memcg, int nid, int shrinker_id) > > } > > } > > > > -/* > > - * We allow subsystems to populate their shrinker-related > > - * LRU lists before register_shrinker_prepared() is called > > - * for the shrinker, since we don't want to impose > > - * restrictions on their internal registration order. > > - * In this case shrink_slab_memcg() may find corresponding > > - * bit is set in the shrinkers map. > > - * > > - * This value is used by the function to detect registering > > - * shrinkers and to skip do_shrink_slab() calls for them. > > - */ > > -#define SHRINKER_REGISTERING ((struct shrinker *)~0UL) > > - > > static DEFINE_IDR(shrinker_idr); > > > > static int prealloc_memcg_shrinker(struct shrinker *shrinker) > > @@ -336,7 +323,7 @@ static int prealloc_memcg_shrinker(struct shrinker *shrinker) > > > > down_write(&shrinker_rwsem); > > /* This may call shrinker, so it must use down_read_trylock() */ > > - id = idr_alloc(&shrinker_idr, SHRINKER_REGISTERING, 0, 0, GFP_KERNEL); > > + id = idr_alloc(&shrinker_idr, shrinker, 0, 0, GFP_KERNEL); > > if (id < 0) > > goto unlock; > > > > @@ -499,10 +486,7 @@ void register_shrinker_prepared(struct shrinker *shrinker) > > { > > down_write(&shrinker_rwsem); > > list_add_tail(&shrinker->list, &shrinker_list); > > -#ifdef CONFIG_MEMCG > > - if (shrinker->flags & SHRINKER_MEMCG_AWARE) > > - idr_replace(&shrinker_idr, shrinker, shrinker->id); > > -#endif > > + shrinker->flags |= SHRINKER_REGISTERED; > > up_write(&shrinker_rwsem); > > } > > > > @@ -522,13 +506,16 @@ EXPORT_SYMBOL(register_shrinker); > > */ > > void unregister_shrinker(struct shrinker *shrinker) > > { > > - if (!shrinker->nr_deferred) > > + if (!(shrinker->flags & SHRINKER_REGISTERED)) > > return; > > - if (shrinker->flags & SHRINKER_MEMCG_AWARE) > > - unregister_memcg_shrinker(shrinker); > > + > > down_write(&shrinker_rwsem); > > list_del(&shrinker->list); > > + shrinker->flags &= ~SHRINKER_REGISTERED; > > up_write(&shrinker_rwsem); > > + > > + if (shrinker->flags & SHRINKER_MEMCG_AWARE) > > + unregister_memcg_shrinker(shrinker); > > Because unregister_memcg_shrinker() will take and release shrinker_rwsem once again, > I wonder if it's better to move it into the locked section and change the calling > convention to require the caller to take the semaphore? BTW, I think lockdep_assert_held() in unregister_memcg_shrinker() seems good enough. > > > kfree(shrinkrem->nr_deferred); > > shrinker->nr_deferred = NULL; > > } > > @@ -693,7 +680,7 @@ static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid, > > struct shrinker *shrinker; > > > > shrinker = idr_find(&shrinker_idr, i); > > - if (unlikely(!shrinker || shrinker == SHRINKER_REGISTERING)) { > > + if (unlikely(!shrinker || !(shrinker->flags & SHRINKER_REGISTERED))) { > > if (!shrinker) > > clear_bit(i, info->map); > > continue; > > -- > > 2.26.2 > >
diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h index 0f80123650e2..1eac79ce57d4 100644 --- a/include/linux/shrinker.h +++ b/include/linux/shrinker.h @@ -79,13 +79,14 @@ struct shrinker { #define DEFAULT_SEEKS 2 /* A good number if you don't know better. */ /* Flags */ -#define SHRINKER_NUMA_AWARE (1 << 0) -#define SHRINKER_MEMCG_AWARE (1 << 1) +#define SHRINKER_REGISTERED (1 << 0) +#define SHRINKER_NUMA_AWARE (1 << 1) +#define SHRINKER_MEMCG_AWARE (1 << 2) /* * It just makes sense when the shrinker is also MEMCG_AWARE for now, * non-MEMCG_AWARE shrinker should not have this flag set. */ -#define SHRINKER_NONSLAB (1 << 2) +#define SHRINKER_NONSLAB (1 << 3) extern int prealloc_shrinker(struct shrinker *shrinker); extern void register_shrinker_prepared(struct shrinker *shrinker); diff --git a/mm/vmscan.c b/mm/vmscan.c index 273efbf4d53c..a047980536cf 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -315,19 +315,6 @@ void set_shrinker_bit(struct mem_cgroup *memcg, int nid, int shrinker_id) } } -/* - * We allow subsystems to populate their shrinker-related - * LRU lists before register_shrinker_prepared() is called - * for the shrinker, since we don't want to impose - * restrictions on their internal registration order. - * In this case shrink_slab_memcg() may find corresponding - * bit is set in the shrinkers map. - * - * This value is used by the function to detect registering - * shrinkers and to skip do_shrink_slab() calls for them. - */ -#define SHRINKER_REGISTERING ((struct shrinker *)~0UL) - static DEFINE_IDR(shrinker_idr); static int prealloc_memcg_shrinker(struct shrinker *shrinker) @@ -336,7 +323,7 @@ static int prealloc_memcg_shrinker(struct shrinker *shrinker) down_write(&shrinker_rwsem); /* This may call shrinker, so it must use down_read_trylock() */ - id = idr_alloc(&shrinker_idr, SHRINKER_REGISTERING, 0, 0, GFP_KERNEL); + id = idr_alloc(&shrinker_idr, shrinker, 0, 0, GFP_KERNEL); if (id < 0) goto unlock; @@ -499,10 +486,7 @@ void register_shrinker_prepared(struct shrinker *shrinker) { down_write(&shrinker_rwsem); list_add_tail(&shrinker->list, &shrinker_list); -#ifdef CONFIG_MEMCG - if (shrinker->flags & SHRINKER_MEMCG_AWARE) - idr_replace(&shrinker_idr, shrinker, shrinker->id); -#endif + shrinker->flags |= SHRINKER_REGISTERED; up_write(&shrinker_rwsem); } @@ -522,13 +506,16 @@ EXPORT_SYMBOL(register_shrinker); */ void unregister_shrinker(struct shrinker *shrinker) { - if (!shrinker->nr_deferred) + if (!(shrinker->flags & SHRINKER_REGISTERED)) return; - if (shrinker->flags & SHRINKER_MEMCG_AWARE) - unregister_memcg_shrinker(shrinker); + down_write(&shrinker_rwsem); list_del(&shrinker->list); + shrinker->flags &= ~SHRINKER_REGISTERED; up_write(&shrinker_rwsem); + + if (shrinker->flags & SHRINKER_MEMCG_AWARE) + unregister_memcg_shrinker(shrinker); kfree(shrinker->nr_deferred); shrinker->nr_deferred = NULL; } @@ -693,7 +680,7 @@ static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid, struct shrinker *shrinker; shrinker = idr_find(&shrinker_idr, i); - if (unlikely(!shrinker || shrinker == SHRINKER_REGISTERING)) { + if (unlikely(!shrinker || !(shrinker->flags & SHRINKER_REGISTERED))) { if (!shrinker) clear_bit(i, info->map); continue;