From e4c057d02c9ef0b39bb88544b0c3c0a0a4d55ed6 Mon Sep 17 00:00:00 2001 From: Jason Gunthorpe Date: Tue, 6 Aug 2019 20:15:41 -0300 Subject: [PATCH] misc/sgi-gru: use mmu_notifier_get/put for struct gru_mm_struct GRU is already using almost the same algorithm as get/put, it even helpfully has a 10 year old comment to make this algorithm common, which is finally happening. There are a few differences and fixes from this conversion: - GRU used rcu not srcu to read the hlist - Unclear how the locking worked to prevent gru_register_mmu_notifier() from running concurrently with gru_drop_mmu_notifier() - this version is safe - GRU had a release function which only set a variable without any locking that skiped the synchronize_srcu during unregister which looks racey, but this makes it reliable via the integrated call_srcu(). - It is unclear if the mmap_sem is actually held when __mmu_notifier_register() was called, lockdep will now warn if this is wrong Link: https://lore.kernel.org/r/20190806231548.25242-5-jgg@ziepe.ca Reviewed-by: Christoph Hellwig Reviewed-by: Dimitri Sivanich Signed-off-by: Jason Gunthorpe --- drivers/misc/sgi-gru/grufile.c | 1 + drivers/misc/sgi-gru/grutables.h | 2 - drivers/misc/sgi-gru/grutlbpurge.c | 82 +++++++++--------------------- 3 files changed, 24 insertions(+), 61 deletions(-) diff --git a/drivers/misc/sgi-gru/grufile.c b/drivers/misc/sgi-gru/grufile.c index a2a142ae087b..9d042310214f 100644 --- a/drivers/misc/sgi-gru/grufile.c +++ b/drivers/misc/sgi-gru/grufile.c @@ -573,6 +573,7 @@ static void __exit gru_exit(void) gru_free_tables(); misc_deregister(&gru_miscdev); gru_proc_exit(); + mmu_notifier_synchronize(); } static const struct file_operations gru_fops = { diff --git a/drivers/misc/sgi-gru/grutables.h b/drivers/misc/sgi-gru/grutables.h index 438191c22057..a7e44b2eb413 100644 --- a/drivers/misc/sgi-gru/grutables.h +++ b/drivers/misc/sgi-gru/grutables.h @@ -307,10 +307,8 @@ struct gru_mm_tracker { /* pack to reduce size */ struct gru_mm_struct { struct mmu_notifier ms_notifier; - atomic_t ms_refcnt; spinlock_t ms_asid_lock; /* protects ASID assignment */ atomic_t ms_range_active;/* num range_invals active */ - char ms_released; wait_queue_head_t ms_wait_queue; DECLARE_BITMAP(ms_asidmap, GRU_MAX_GRUS); struct gru_mm_tracker ms_asids[GRU_MAX_GRUS]; diff --git a/drivers/misc/sgi-gru/grutlbpurge.c b/drivers/misc/sgi-gru/grutlbpurge.c index 59ba0adf23ce..10921cd2608d 100644 --- a/drivers/misc/sgi-gru/grutlbpurge.c +++ b/drivers/misc/sgi-gru/grutlbpurge.c @@ -235,83 +235,47 @@ static void gru_invalidate_range_end(struct mmu_notifier *mn, gms, range->start, range->end); } -static void gru_release(struct mmu_notifier *mn, struct mm_struct *mm) +static struct mmu_notifier *gru_alloc_notifier(struct mm_struct *mm) { - struct gru_mm_struct *gms = container_of(mn, struct gru_mm_struct, - ms_notifier); + struct gru_mm_struct *gms; - gms->ms_released = 1; - gru_dbg(grudev, "gms %p\n", gms); + gms = kzalloc(sizeof(*gms), GFP_KERNEL); + if (!gms) + return ERR_PTR(-ENOMEM); + STAT(gms_alloc); + spin_lock_init(&gms->ms_asid_lock); + init_waitqueue_head(&gms->ms_wait_queue); + + return &gms->ms_notifier; } +static void gru_free_notifier(struct mmu_notifier *mn) +{ + kfree(container_of(mn, struct gru_mm_struct, ms_notifier)); + STAT(gms_free); +} static const struct mmu_notifier_ops gru_mmuops = { .invalidate_range_start = gru_invalidate_range_start, .invalidate_range_end = gru_invalidate_range_end, - .release = gru_release, + .alloc_notifier = gru_alloc_notifier, + .free_notifier = gru_free_notifier, }; -/* Move this to the basic mmu_notifier file. But for now... */ -static struct mmu_notifier *mmu_find_ops(struct mm_struct *mm, - const struct mmu_notifier_ops *ops) -{ - struct mmu_notifier *mn, *gru_mn = NULL; - - if (mm->mmu_notifier_mm) { - rcu_read_lock(); - hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, - hlist) - if (mn->ops == ops) { - gru_mn = mn; - break; - } - rcu_read_unlock(); - } - return gru_mn; -} - struct gru_mm_struct *gru_register_mmu_notifier(void) { - struct gru_mm_struct *gms; struct mmu_notifier *mn; - int err; - mn = mmu_find_ops(current->mm, &gru_mmuops); - if (mn) { - gms = container_of(mn, struct gru_mm_struct, ms_notifier); - atomic_inc(&gms->ms_refcnt); - } else { - gms = kzalloc(sizeof(*gms), GFP_KERNEL); - if (!gms) - return ERR_PTR(-ENOMEM); - STAT(gms_alloc); - spin_lock_init(&gms->ms_asid_lock); - gms->ms_notifier.ops = &gru_mmuops; - atomic_set(&gms->ms_refcnt, 1); - init_waitqueue_head(&gms->ms_wait_queue); - err = __mmu_notifier_register(&gms->ms_notifier, current->mm); - if (err) - goto error; - } - if (gms) - gru_dbg(grudev, "gms %p, refcnt %d\n", gms, - atomic_read(&gms->ms_refcnt)); - return gms; -error: - kfree(gms); - return ERR_PTR(err); + mn = mmu_notifier_get_locked(&gru_mmuops, current->mm); + if (IS_ERR(mn)) + return ERR_CAST(mn); + + return container_of(mn, struct gru_mm_struct, ms_notifier); } void gru_drop_mmu_notifier(struct gru_mm_struct *gms) { - gru_dbg(grudev, "gms %p, refcnt %d, released %d\n", gms, - atomic_read(&gms->ms_refcnt), gms->ms_released); - if (atomic_dec_return(&gms->ms_refcnt) == 0) { - if (!gms->ms_released) - mmu_notifier_unregister(&gms->ms_notifier, current->mm); - kfree(gms); - STAT(gms_free); - } + mmu_notifier_put(&gms->ms_notifier); } /*