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hmm: use mmu_notifier_get/put for 'struct hmm'

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This is a significant simplification, it eliminates all the remaining
'hmm' stuff in mm_struct, eliminates krefing along the critical notifier
paths, and takes away all the ugly locking and abuse of page_table_lock.

mmu_notifier_get() provides the single struct hmm per struct mm which
eliminates mm->hmm.

It also directly guarantees that no mmu_notifier op callback is callable
while concurrent free is possible, this eliminates all the krefs inside
the mmu_notifier callbacks.

The remaining krefs in the range code were overly cautious, drivers are
already not permitted to free the mirror while a range exists.

Link: https://lore.kernel.org/r/20190806231548.25242-6-jgg@ziepe.ca
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ralph Campbell <rcampbell@nvidia.com>
Tested-by: Ralph Campbell <rcampbell@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
This commit is contained in:
Jason Gunthorpe
2019-08-06 20:15:42 -03:00
parent e4c057d02c
commit c7d8b7824f
6 changed files with 34 additions and 111 deletions
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12
include/linux/hmm.h
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@@ -84,15 +84,12 @@
* @notifiers: count of active mmu notifiers
*/
struct hmm {
struct mm_struct *mm;
struct kref kref;
struct mmu_notifier mmu_notifier;
spinlock_t ranges_lock;
struct list_head ranges;
struct list_head mirrors;
struct mmu_notifier mmu_notifier;
struct rw_semaphore mirrors_sem;
wait_queue_head_t wq;
struct rcu_head rcu;
long notifiers;
};
@@ -409,13 +406,6 @@ long hmm_range_dma_unmap(struct hmm_range *range,
*/
#define HMM_RANGE_DEFAULT_TIMEOUT 1000
/* Below are for HMM internal use only! Not to be used by device driver! */
static inline void hmm_mm_init(struct mm_struct *mm)
{
mm->hmm = NULL;
}
#else /* IS_ENABLED(CONFIG_HMM_MIRROR) */
static inline void hmm_mm_init(struct mm_struct *mm) {}
#endif /* IS_ENABLED(CONFIG_HMM_MIRROR) */
#endif /* LINUX_HMM_H */