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![Jason Gunthorpe](/assets/img/avatar_default.png)
The return code from the op callback is actually in _ret, while the
WARN_ON was checking ret which causes it to misfire.
Link: http://lkml.kernel.org/r/20191025175502.GA31127@ziepe.ca
Fixes: 8402ce61be
("mm/mmu_notifiers: check if mmu notifier callbacks are allowed to fail")
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
546 lines
16 KiB
C
546 lines
16 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* linux/mm/mmu_notifier.c
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*
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* Copyright (C) 2008 Qumranet, Inc.
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* Copyright (C) 2008 SGI
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* Christoph Lameter <cl@linux.com>
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*/
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#include <linux/rculist.h>
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#include <linux/mmu_notifier.h>
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#include <linux/export.h>
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#include <linux/mm.h>
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#include <linux/err.h>
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#include <linux/srcu.h>
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#include <linux/rcupdate.h>
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#include <linux/sched.h>
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#include <linux/sched/mm.h>
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#include <linux/slab.h>
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/* global SRCU for all MMs */
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DEFINE_STATIC_SRCU(srcu);
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#ifdef CONFIG_LOCKDEP
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struct lockdep_map __mmu_notifier_invalidate_range_start_map = {
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.name = "mmu_notifier_invalidate_range_start"
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};
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#endif
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/*
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* This function can't run concurrently against mmu_notifier_register
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* because mm->mm_users > 0 during mmu_notifier_register and exit_mmap
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* runs with mm_users == 0. Other tasks may still invoke mmu notifiers
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* in parallel despite there being no task using this mm any more,
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* through the vmas outside of the exit_mmap context, such as with
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* vmtruncate. This serializes against mmu_notifier_unregister with
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* the mmu_notifier_mm->lock in addition to SRCU and it serializes
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* against the other mmu notifiers with SRCU. struct mmu_notifier_mm
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* can't go away from under us as exit_mmap holds an mm_count pin
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* itself.
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*/
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void __mmu_notifier_release(struct mm_struct *mm)
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{
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struct mmu_notifier *mn;
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int id;
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/*
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* SRCU here will block mmu_notifier_unregister until
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* ->release returns.
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*/
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id = srcu_read_lock(&srcu);
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hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist)
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/*
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* If ->release runs before mmu_notifier_unregister it must be
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* handled, as it's the only way for the driver to flush all
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* existing sptes and stop the driver from establishing any more
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* sptes before all the pages in the mm are freed.
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*/
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if (mn->ops->release)
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mn->ops->release(mn, mm);
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spin_lock(&mm->mmu_notifier_mm->lock);
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while (unlikely(!hlist_empty(&mm->mmu_notifier_mm->list))) {
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mn = hlist_entry(mm->mmu_notifier_mm->list.first,
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struct mmu_notifier,
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hlist);
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/*
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* We arrived before mmu_notifier_unregister so
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* mmu_notifier_unregister will do nothing other than to wait
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* for ->release to finish and for mmu_notifier_unregister to
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* return.
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*/
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hlist_del_init_rcu(&mn->hlist);
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}
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spin_unlock(&mm->mmu_notifier_mm->lock);
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srcu_read_unlock(&srcu, id);
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/*
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* synchronize_srcu here prevents mmu_notifier_release from returning to
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* exit_mmap (which would proceed with freeing all pages in the mm)
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* until the ->release method returns, if it was invoked by
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* mmu_notifier_unregister.
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*
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* The mmu_notifier_mm can't go away from under us because one mm_count
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* is held by exit_mmap.
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*/
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synchronize_srcu(&srcu);
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}
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/*
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* If no young bitflag is supported by the hardware, ->clear_flush_young can
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* unmap the address and return 1 or 0 depending if the mapping previously
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* existed or not.
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*/
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int __mmu_notifier_clear_flush_young(struct mm_struct *mm,
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unsigned long start,
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unsigned long end)
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{
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struct mmu_notifier *mn;
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int young = 0, id;
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id = srcu_read_lock(&srcu);
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hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
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if (mn->ops->clear_flush_young)
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young |= mn->ops->clear_flush_young(mn, mm, start, end);
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}
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srcu_read_unlock(&srcu, id);
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return young;
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}
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int __mmu_notifier_clear_young(struct mm_struct *mm,
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unsigned long start,
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unsigned long end)
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{
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struct mmu_notifier *mn;
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int young = 0, id;
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id = srcu_read_lock(&srcu);
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hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
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if (mn->ops->clear_young)
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young |= mn->ops->clear_young(mn, mm, start, end);
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}
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srcu_read_unlock(&srcu, id);
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return young;
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}
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int __mmu_notifier_test_young(struct mm_struct *mm,
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unsigned long address)
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{
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struct mmu_notifier *mn;
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int young = 0, id;
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id = srcu_read_lock(&srcu);
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hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
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if (mn->ops->test_young) {
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young = mn->ops->test_young(mn, mm, address);
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if (young)
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break;
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}
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}
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srcu_read_unlock(&srcu, id);
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return young;
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}
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void __mmu_notifier_change_pte(struct mm_struct *mm, unsigned long address,
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pte_t pte)
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{
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struct mmu_notifier *mn;
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int id;
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id = srcu_read_lock(&srcu);
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hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
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if (mn->ops->change_pte)
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mn->ops->change_pte(mn, mm, address, pte);
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}
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srcu_read_unlock(&srcu, id);
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}
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int __mmu_notifier_invalidate_range_start(struct mmu_notifier_range *range)
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{
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struct mmu_notifier *mn;
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int ret = 0;
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int id;
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id = srcu_read_lock(&srcu);
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hlist_for_each_entry_rcu(mn, &range->mm->mmu_notifier_mm->list, hlist) {
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if (mn->ops->invalidate_range_start) {
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int _ret;
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if (!mmu_notifier_range_blockable(range))
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non_block_start();
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_ret = mn->ops->invalidate_range_start(mn, range);
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if (!mmu_notifier_range_blockable(range))
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non_block_end();
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if (_ret) {
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pr_info("%pS callback failed with %d in %sblockable context.\n",
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mn->ops->invalidate_range_start, _ret,
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!mmu_notifier_range_blockable(range) ? "non-" : "");
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WARN_ON(mmu_notifier_range_blockable(range) ||
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_ret != -EAGAIN);
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ret = _ret;
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}
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}
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}
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srcu_read_unlock(&srcu, id);
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return ret;
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}
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void __mmu_notifier_invalidate_range_end(struct mmu_notifier_range *range,
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bool only_end)
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{
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struct mmu_notifier *mn;
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int id;
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lock_map_acquire(&__mmu_notifier_invalidate_range_start_map);
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id = srcu_read_lock(&srcu);
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hlist_for_each_entry_rcu(mn, &range->mm->mmu_notifier_mm->list, hlist) {
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/*
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* Call invalidate_range here too to avoid the need for the
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* subsystem of having to register an invalidate_range_end
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* call-back when there is invalidate_range already. Usually a
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* subsystem registers either invalidate_range_start()/end() or
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* invalidate_range(), so this will be no additional overhead
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* (besides the pointer check).
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*
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* We skip call to invalidate_range() if we know it is safe ie
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* call site use mmu_notifier_invalidate_range_only_end() which
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* is safe to do when we know that a call to invalidate_range()
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* already happen under page table lock.
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*/
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if (!only_end && mn->ops->invalidate_range)
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mn->ops->invalidate_range(mn, range->mm,
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range->start,
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range->end);
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if (mn->ops->invalidate_range_end) {
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if (!mmu_notifier_range_blockable(range))
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non_block_start();
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mn->ops->invalidate_range_end(mn, range);
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if (!mmu_notifier_range_blockable(range))
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non_block_end();
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}
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}
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srcu_read_unlock(&srcu, id);
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lock_map_release(&__mmu_notifier_invalidate_range_start_map);
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}
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void __mmu_notifier_invalidate_range(struct mm_struct *mm,
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unsigned long start, unsigned long end)
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{
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struct mmu_notifier *mn;
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int id;
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id = srcu_read_lock(&srcu);
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hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
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if (mn->ops->invalidate_range)
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mn->ops->invalidate_range(mn, mm, start, end);
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}
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srcu_read_unlock(&srcu, id);
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}
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/*
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* Same as mmu_notifier_register but here the caller must hold the
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* mmap_sem in write mode.
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*/
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int __mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm)
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{
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struct mmu_notifier_mm *mmu_notifier_mm = NULL;
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int ret;
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lockdep_assert_held_write(&mm->mmap_sem);
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BUG_ON(atomic_read(&mm->mm_users) <= 0);
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if (IS_ENABLED(CONFIG_LOCKDEP)) {
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fs_reclaim_acquire(GFP_KERNEL);
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lock_map_acquire(&__mmu_notifier_invalidate_range_start_map);
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lock_map_release(&__mmu_notifier_invalidate_range_start_map);
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fs_reclaim_release(GFP_KERNEL);
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}
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mn->mm = mm;
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mn->users = 1;
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if (!mm->mmu_notifier_mm) {
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/*
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* kmalloc cannot be called under mm_take_all_locks(), but we
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* know that mm->mmu_notifier_mm can't change while we hold
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* the write side of the mmap_sem.
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*/
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mmu_notifier_mm =
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kmalloc(sizeof(struct mmu_notifier_mm), GFP_KERNEL);
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if (!mmu_notifier_mm)
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return -ENOMEM;
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INIT_HLIST_HEAD(&mmu_notifier_mm->list);
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spin_lock_init(&mmu_notifier_mm->lock);
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}
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ret = mm_take_all_locks(mm);
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if (unlikely(ret))
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goto out_clean;
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/* Pairs with the mmdrop in mmu_notifier_unregister_* */
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mmgrab(mm);
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/*
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* Serialize the update against mmu_notifier_unregister. A
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* side note: mmu_notifier_release can't run concurrently with
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* us because we hold the mm_users pin (either implicitly as
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* current->mm or explicitly with get_task_mm() or similar).
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* We can't race against any other mmu notifier method either
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* thanks to mm_take_all_locks().
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*/
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if (mmu_notifier_mm)
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mm->mmu_notifier_mm = mmu_notifier_mm;
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spin_lock(&mm->mmu_notifier_mm->lock);
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hlist_add_head_rcu(&mn->hlist, &mm->mmu_notifier_mm->list);
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spin_unlock(&mm->mmu_notifier_mm->lock);
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mm_drop_all_locks(mm);
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BUG_ON(atomic_read(&mm->mm_users) <= 0);
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return 0;
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out_clean:
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kfree(mmu_notifier_mm);
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return ret;
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}
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EXPORT_SYMBOL_GPL(__mmu_notifier_register);
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/**
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* mmu_notifier_register - Register a notifier on a mm
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* @mn: The notifier to attach
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* @mm: The mm to attach the notifier to
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*
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* Must not hold mmap_sem nor any other VM related lock when calling
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* this registration function. Must also ensure mm_users can't go down
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* to zero while this runs to avoid races with mmu_notifier_release,
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* so mm has to be current->mm or the mm should be pinned safely such
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* as with get_task_mm(). If the mm is not current->mm, the mm_users
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* pin should be released by calling mmput after mmu_notifier_register
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* returns.
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*
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* mmu_notifier_unregister() or mmu_notifier_put() must be always called to
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* unregister the notifier.
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*
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* While the caller has a mmu_notifier get the mn->mm pointer will remain
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* valid, and can be converted to an active mm pointer via mmget_not_zero().
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*/
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int mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm)
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{
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int ret;
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down_write(&mm->mmap_sem);
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ret = __mmu_notifier_register(mn, mm);
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up_write(&mm->mmap_sem);
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return ret;
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}
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EXPORT_SYMBOL_GPL(mmu_notifier_register);
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static struct mmu_notifier *
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find_get_mmu_notifier(struct mm_struct *mm, const struct mmu_notifier_ops *ops)
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{
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struct mmu_notifier *mn;
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spin_lock(&mm->mmu_notifier_mm->lock);
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hlist_for_each_entry_rcu (mn, &mm->mmu_notifier_mm->list, hlist) {
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if (mn->ops != ops)
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continue;
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if (likely(mn->users != UINT_MAX))
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mn->users++;
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else
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mn = ERR_PTR(-EOVERFLOW);
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spin_unlock(&mm->mmu_notifier_mm->lock);
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return mn;
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}
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spin_unlock(&mm->mmu_notifier_mm->lock);
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return NULL;
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}
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/**
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* mmu_notifier_get_locked - Return the single struct mmu_notifier for
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* the mm & ops
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* @ops: The operations struct being subscribe with
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* @mm : The mm to attach notifiers too
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*
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* This function either allocates a new mmu_notifier via
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* ops->alloc_notifier(), or returns an already existing notifier on the
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* list. The value of the ops pointer is used to determine when two notifiers
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* are the same.
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*
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* Each call to mmu_notifier_get() must be paired with a call to
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* mmu_notifier_put(). The caller must hold the write side of mm->mmap_sem.
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*
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* While the caller has a mmu_notifier get the mm pointer will remain valid,
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* and can be converted to an active mm pointer via mmget_not_zero().
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*/
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struct mmu_notifier *mmu_notifier_get_locked(const struct mmu_notifier_ops *ops,
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struct mm_struct *mm)
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{
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struct mmu_notifier *mn;
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int ret;
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lockdep_assert_held_write(&mm->mmap_sem);
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if (mm->mmu_notifier_mm) {
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mn = find_get_mmu_notifier(mm, ops);
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if (mn)
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return mn;
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}
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mn = ops->alloc_notifier(mm);
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if (IS_ERR(mn))
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return mn;
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mn->ops = ops;
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ret = __mmu_notifier_register(mn, mm);
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if (ret)
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goto out_free;
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return mn;
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out_free:
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mn->ops->free_notifier(mn);
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return ERR_PTR(ret);
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}
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EXPORT_SYMBOL_GPL(mmu_notifier_get_locked);
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/* this is called after the last mmu_notifier_unregister() returned */
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void __mmu_notifier_mm_destroy(struct mm_struct *mm)
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{
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BUG_ON(!hlist_empty(&mm->mmu_notifier_mm->list));
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kfree(mm->mmu_notifier_mm);
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mm->mmu_notifier_mm = LIST_POISON1; /* debug */
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}
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/*
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* This releases the mm_count pin automatically and frees the mm
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* structure if it was the last user of it. It serializes against
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* running mmu notifiers with SRCU and against mmu_notifier_unregister
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* with the unregister lock + SRCU. All sptes must be dropped before
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* calling mmu_notifier_unregister. ->release or any other notifier
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* method may be invoked concurrently with mmu_notifier_unregister,
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* and only after mmu_notifier_unregister returned we're guaranteed
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* that ->release or any other method can't run anymore.
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*/
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void mmu_notifier_unregister(struct mmu_notifier *mn, struct mm_struct *mm)
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{
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BUG_ON(atomic_read(&mm->mm_count) <= 0);
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if (!hlist_unhashed(&mn->hlist)) {
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/*
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* SRCU here will force exit_mmap to wait for ->release to
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* finish before freeing the pages.
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*/
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int id;
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id = srcu_read_lock(&srcu);
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/*
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* exit_mmap will block in mmu_notifier_release to guarantee
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* that ->release is called before freeing the pages.
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*/
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if (mn->ops->release)
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mn->ops->release(mn, mm);
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srcu_read_unlock(&srcu, id);
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spin_lock(&mm->mmu_notifier_mm->lock);
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/*
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* Can not use list_del_rcu() since __mmu_notifier_release
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* can delete it before we hold the lock.
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*/
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hlist_del_init_rcu(&mn->hlist);
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spin_unlock(&mm->mmu_notifier_mm->lock);
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}
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/*
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* Wait for any running method to finish, of course including
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* ->release if it was run by mmu_notifier_release instead of us.
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*/
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synchronize_srcu(&srcu);
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BUG_ON(atomic_read(&mm->mm_count) <= 0);
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mmdrop(mm);
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}
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EXPORT_SYMBOL_GPL(mmu_notifier_unregister);
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|
static void mmu_notifier_free_rcu(struct rcu_head *rcu)
|
|
{
|
|
struct mmu_notifier *mn = container_of(rcu, struct mmu_notifier, rcu);
|
|
struct mm_struct *mm = mn->mm;
|
|
|
|
mn->ops->free_notifier(mn);
|
|
/* Pairs with the get in __mmu_notifier_register() */
|
|
mmdrop(mm);
|
|
}
|
|
|
|
/**
|
|
* mmu_notifier_put - Release the reference on the notifier
|
|
* @mn: The notifier to act on
|
|
*
|
|
* This function must be paired with each mmu_notifier_get(), it releases the
|
|
* reference obtained by the get. If this is the last reference then process
|
|
* to free the notifier will be run asynchronously.
|
|
*
|
|
* Unlike mmu_notifier_unregister() the get/put flow only calls ops->release
|
|
* when the mm_struct is destroyed. Instead free_notifier is always called to
|
|
* release any resources held by the user.
|
|
*
|
|
* As ops->release is not guaranteed to be called, the user must ensure that
|
|
* all sptes are dropped, and no new sptes can be established before
|
|
* mmu_notifier_put() is called.
|
|
*
|
|
* This function can be called from the ops->release callback, however the
|
|
* caller must still ensure it is called pairwise with mmu_notifier_get().
|
|
*
|
|
* Modules calling this function must call mmu_notifier_synchronize() in
|
|
* their __exit functions to ensure the async work is completed.
|
|
*/
|
|
void mmu_notifier_put(struct mmu_notifier *mn)
|
|
{
|
|
struct mm_struct *mm = mn->mm;
|
|
|
|
spin_lock(&mm->mmu_notifier_mm->lock);
|
|
if (WARN_ON(!mn->users) || --mn->users)
|
|
goto out_unlock;
|
|
hlist_del_init_rcu(&mn->hlist);
|
|
spin_unlock(&mm->mmu_notifier_mm->lock);
|
|
|
|
call_srcu(&srcu, &mn->rcu, mmu_notifier_free_rcu);
|
|
return;
|
|
|
|
out_unlock:
|
|
spin_unlock(&mm->mmu_notifier_mm->lock);
|
|
}
|
|
EXPORT_SYMBOL_GPL(mmu_notifier_put);
|
|
|
|
/**
|
|
* mmu_notifier_synchronize - Ensure all mmu_notifiers are freed
|
|
*
|
|
* This function ensures that all outstanding async SRU work from
|
|
* mmu_notifier_put() is completed. After it returns any mmu_notifier_ops
|
|
* associated with an unused mmu_notifier will no longer be called.
|
|
*
|
|
* Before using the caller must ensure that all of its mmu_notifiers have been
|
|
* fully released via mmu_notifier_put().
|
|
*
|
|
* Modules using the mmu_notifier_put() API should call this in their __exit
|
|
* function to avoid module unloading races.
|
|
*/
|
|
void mmu_notifier_synchronize(void)
|
|
{
|
|
synchronize_srcu(&srcu);
|
|
}
|
|
EXPORT_SYMBOL_GPL(mmu_notifier_synchronize);
|
|
|
|
bool
|
|
mmu_notifier_range_update_to_read_only(const struct mmu_notifier_range *range)
|
|
{
|
|
if (!range->vma || range->event != MMU_NOTIFY_PROTECTION_VMA)
|
|
return false;
|
|
/* Return true if the vma still have the read flag set. */
|
|
return range->vma->vm_flags & VM_READ;
|
|
}
|
|
EXPORT_SYMBOL_GPL(mmu_notifier_range_update_to_read_only);
|