[PATCH 03/22] mm/hmm: clean up some coding style and comments

Christoph Hellwig
2019-07-01T06:20:33Z

From: Ralph Campbell <rcampbell@nvidia.com>

There are no functional changes, just some coding style clean ups and
minor comment changes.

Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Souptick Joarder <jrdr.linux@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ralph Campbell <rcampbell@nvidia.com>
Reviewed-by: Jérôme Glisse <jglisse@redhat.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
---
include/linux/hmm.h | 71 +++++++++++++++++++++++----------------------
mm/hmm.c | 62 ++++++++++++++++++++-------------------
2 files changed, 68 insertions(+), 65 deletions(-)

diff --git a/include/linux/hmm.h b/include/linux/hmm.h
index 740bb00853f5..7007123842ba 100644
--- a/include/linux/hmm.h
+++ b/include/linux/hmm.h
@@ -21,8 +21,8 @@
*
* HMM address space mirroring API:
*
- * Use HMM address space mirroring if you want to mirror range of the CPU page
- * table of a process into a device page table. Here, "mirror" means "keep
+ * Use HMM address space mirroring if you want to mirror a range of the CPU
+ * page tables of a process into a device page table. Here, "mirror" means "keep
* synchronized". Prerequisites: the device must provide the ability to write-
* protect its page tables (at PAGE_SIZE granularity), and must be able to
* recover from the resulting potential page faults.
@@ -105,10 +105,11 @@ struct hmm {
* HMM_PFN_WRITE: CPU page table has write permission set
* HMM_PFN_DEVICE_PRIVATE: private device memory (ZONE_DEVICE)
*
- * The driver provide a flags array, if driver valid bit for an entry is bit
- * 3 ie (entry & (1 << 3)) is true if entry is valid then driver must provide
+ * The driver provides a flags array for mapping page protections to device
+ * PTE bits. If the driver valid bit for an entry is bit 3,
+ * i.e., (entry & (1 << 3)), then the driver must provide
* an array in hmm_range.flags with hmm_range.flags[HMM_PFN_VALID] == 1 << 3.
- * Same logic apply to all flags. This is same idea as vm_page_prot in vma
+ * Same logic apply to all flags. This is the same idea as vm_page_prot in vma
* except that this is per device driver rather than per architecture.
*/
enum hmm_pfn_flag_e {
@@ -129,13 +130,13 @@ enum hmm_pfn_flag_e {
* be mirrored by a device, because the entry will never have HMM_PFN_VALID
* set and the pfn value is undefined.
*
- * Driver provide entry value for none entry, error entry and special entry,
- * driver can alias (ie use same value for error and special for instance). It
- * should not alias none and error or special.
+ * Driver provides values for none entry, error entry, and special entry.
+ * Driver can alias (i.e., use same value) error and special, but
+ * it should not alias none with error or special.
*
* HMM pfn value returned by hmm_vma_get_pfns() or hmm_vma_fault() will be:
* hmm_range.values[HMM_PFN_ERROR] if CPU page table entry is poisonous,
- * hmm_range.values[HMM_PFN_NONE] if there is no CPU page table
+ * hmm_range.values[HMM_PFN_NONE] if there is no CPU page table entry,
* hmm_range.values[HMM_PFN_SPECIAL] if CPU page table entry is a special one
*/
enum hmm_pfn_value_e {
@@ -158,6 +159,7 @@ enum hmm_pfn_value_e {
* @values: pfn value for some special case (none, special, error, ...)
* @default_flags: default flags for the range (write, read, ... see hmm doc)
* @pfn_flags_mask: allows to mask pfn flags so that only default_flags matter
+ * @page_shift: device virtual address shift value (should be >= PAGE_SHIFT)
* @pfn_shifts: pfn shift value (should be <= PAGE_SHIFT)
* @valid: pfns array did not change since it has been fill by an HMM function
*/
@@ -180,7 +182,7 @@ struct hmm_range {
/*
* hmm_range_page_shift() - return the page shift for the range
* @range: range being queried
- * Returns: page shift (page size = 1 << page shift) for the range
+ * Return: page shift (page size = 1 << page shift) for the range
*/
static inline unsigned hmm_range_page_shift(const struct hmm_range *range)
{
@@ -190,7 +192,7 @@ static inline unsigned hmm_range_page_shift(const struct hmm_range *range)
/*
* hmm_range_page_size() - return the page size for the range
* @range: range being queried
- * Returns: page size for the range in bytes
+ * Return: page size for the range in bytes
*/
static inline unsigned long hmm_range_page_size(const struct hmm_range *range)
{
@@ -201,7 +203,7 @@ static inline unsigned long hmm_range_page_size(const struct hmm_range *range)
* hmm_range_wait_until_valid() - wait for range to be valid
* @range: range affected by invalidation to wait on
* @timeout: time out for wait in ms (ie abort wait after that period of time)
- * Returns: true if the range is valid, false otherwise.
+ * Return: true if the range is valid, false otherwise.
*/
static inline bool hmm_range_wait_until_valid(struct hmm_range *range,
unsigned long timeout)
@@ -222,7 +224,7 @@ static inline bool hmm_range_wait_until_valid(struct hmm_range *range,
/*
* hmm_range_valid() - test if a range is valid or not
* @range: range
- * Returns: true if the range is valid, false otherwise.
+ * Return: true if the range is valid, false otherwise.
*/
static inline bool hmm_range_valid(struct hmm_range *range)
{
@@ -233,7 +235,7 @@ static inline bool hmm_range_valid(struct hmm_range *range)
* hmm_device_entry_to_page() - return struct page pointed to by a device entry
* @range: range use to decode device entry value
* @entry: device entry value to get corresponding struct page from
- * Returns: struct page pointer if entry is a valid, NULL otherwise
+ * Return: struct page pointer if entry is a valid, NULL otherwise
*
* If the device entry is valid (ie valid flag set) then return the struct page
* matching the entry value. Otherwise return NULL.
@@ -256,7 +258,7 @@ static inline struct page *hmm_device_entry_to_page(const struct hmm_range *rang
* hmm_device_entry_to_pfn() - return pfn value store in a device entry
* @range: range use to decode device entry value
* @entry: device entry to extract pfn from
- * Returns: pfn value if device entry is valid, -1UL otherwise
+ * Return: pfn value if device entry is valid, -1UL otherwise
*/
static inline unsigned long
hmm_device_entry_to_pfn(const struct hmm_range *range, uint64_t pfn)
@@ -276,7 +278,7 @@ hmm_device_entry_to_pfn(const struct hmm_range *range, uint64_t pfn)
* hmm_device_entry_from_page() - create a valid device entry for a page
* @range: range use to encode HMM pfn value
* @page: page for which to create the device entry
- * Returns: valid device entry for the page
+ * Return: valid device entry for the page
*/
static inline uint64_t hmm_device_entry_from_page(const struct hmm_range *range,
struct page *page)
@@ -289,7 +291,7 @@ static inline uint64_t hmm_device_entry_from_page(const struct hmm_range *range,
* hmm_device_entry_from_pfn() - create a valid device entry value from pfn
* @range: range use to encode HMM pfn value
* @pfn: pfn value for which to create the device entry
- * Returns: valid device entry for the pfn
+ * Return: valid device entry for the pfn
*/
static inline uint64_t hmm_device_entry_from_pfn(const struct hmm_range *range,
unsigned long pfn)
@@ -394,7 +396,7 @@ enum hmm_update_event {
};

/*
- * struct hmm_update - HMM update informations for callback
+ * struct hmm_update - HMM update information for callback
*
* @start: virtual start address of the range to update
* @end: virtual end address of the range to update
@@ -428,8 +430,8 @@ struct hmm_mirror_ops {
/* sync_cpu_device_pagetables() - synchronize page tables
*
* @mirror: pointer to struct hmm_mirror
- * @update: update informations (see struct hmm_update)
- * Returns: -EAGAIN if update.blockable false and callback need to
+ * @update: update information (see struct hmm_update)
+ * Return: -EAGAIN if update.blockable false and callback need to
* block, 0 otherwise.
*
* This callback ultimately originates from mmu_notifiers when the CPU
@@ -468,13 +470,13 @@ void hmm_mirror_unregister(struct hmm_mirror *mirror);
/*
* hmm_mirror_mm_is_alive() - test if mm is still alive
* @mirror: the HMM mm mirror for which we want to lock the mmap_sem
- * Returns: false if the mm is dead, true otherwise
+ * Return: false if the mm is dead, true otherwise
*
- * This is an optimization it will not accurately always return -EINVAL if the
- * mm is dead ie there can be false negative (process is being kill but HMM is
- * not yet inform of that). It is only intented to be use to optimize out case
- * where driver is about to do something time consuming and it would be better
- * to skip it if the mm is dead.
+ * This is an optimization, it will not always accurately return false if the
+ * mm is dead; i.e., there can be false negatives (process is being killed but
+ * HMM is not yet informed of that). It is only intended to be used to optimize
+ * out cases where the driver is about to do something time consuming and it
+ * would be better to skip it if the mm is dead.
*/
static inline bool hmm_mirror_mm_is_alive(struct hmm_mirror *mirror)
{
@@ -489,7 +491,6 @@ static inline bool hmm_mirror_mm_is_alive(struct hmm_mirror *mirror)
return true;
}

-
/*
* Please see Documentation/vm/hmm.rst for how to use the range API.
*/
@@ -562,7 +563,7 @@ static inline int hmm_vma_fault(struct hmm_range *range, bool block)
ret = hmm_range_fault(range, block);
if (ret <= 0) {
if (ret == -EBUSY || !ret) {
- /* Same as above drop mmap_sem to match old API. */
+ /* Same as above, drop mmap_sem to match old API. */
up_read(&range->vma->vm_mm->mmap_sem);
ret = -EBUSY;
} else if (ret == -EAGAIN)
@@ -629,7 +630,7 @@ struct hmm_devmem_ops {
* @page: pointer to struct page backing virtual address (unreliable)
* @flags: FAULT_FLAG_* (see include/linux/mm.h)
* @pmdp: page middle directory
- * Returns: VM_FAULT_MINOR/MAJOR on success or one of VM_FAULT_ERROR
+ * Return: VM_FAULT_MINOR/MAJOR on success or one of VM_FAULT_ERROR
* on error
*
* The callback occurs whenever there is a CPU page fault or GUP on a
@@ -637,14 +638,14 @@ struct hmm_devmem_ops {
* page back to regular memory (CPU accessible).
*
* The device driver is free to migrate more than one page from the
- * fault() callback as an optimization. However if device decide to
- * migrate more than one page it must always priotirize the faulting
+ * fault() callback as an optimization. However if the device decides
+ * to migrate more than one page it must always priotirize the faulting
* address over the others.
*
- * The struct page pointer is only given as an hint to allow quick
+ * The struct page pointer is only given as a hint to allow quick
* lookup of internal device driver data. A concurrent migration
- * might have already free that page and the virtual address might
- * not longer be back by it. So it should not be modified by the
+ * might have already freed that page and the virtual address might
+ * no longer be backed by it. So it should not be modified by the
* callback.
*
* Note that mmap semaphore is held in read mode at least when this
@@ -671,7 +672,7 @@ struct hmm_devmem_ops {
* @ref: per CPU refcount
* @page_fault: callback when CPU fault on an unaddressable device page
*
- * This an helper structure for device drivers that do not wish to implement
+ * This is a helper structure for device drivers that do not wish to implement
* the gory details related to hotplugging new memoy and allocating struct
* pages.
*
diff --git a/mm/hmm.c b/mm/hmm.c
index c62ae414a3a2..4db5dcf110ba 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -153,9 +153,8 @@ static void hmm_release(struct mmu_notifier *mn, struct mm_struct *mm)

/* Wake-up everyone waiting on any range. */
mutex_lock(&hmm->lock);
- list_for_each_entry(range, &hmm->ranges, list) {
+ list_for_each_entry(range, &hmm->ranges, list)
range->valid = false;
- }
wake_up_all(&hmm->wq);
mutex_unlock(&hmm->lock);

@@ -166,9 +165,10 @@ static void hmm_release(struct mmu_notifier *mn, struct mm_struct *mm)
list_del_init(&mirror->list);
if (mirror->ops->release) {
/*
- * Drop mirrors_sem so callback can wait on any pending
- * work that might itself trigger mmu_notifier callback
- * and thus would deadlock with us.
+ * Drop mirrors_sem so the release callback can wait
+ * on any pending work that might itself trigger a
+ * mmu_notifier callback and thus would deadlock with
+ * us.
*/
up_write(&hmm->mirrors_sem);
mirror->ops->release(mirror);
@@ -223,11 +223,8 @@ static int hmm_invalidate_range_start(struct mmu_notifier *mn,
int ret;

ret = mirror->ops->sync_cpu_device_pagetables(mirror, &update);
- if (!update.blockable && ret == -EAGAIN) {
- up_read(&hmm->mirrors_sem);
- ret = -EAGAIN;
- goto out;
- }
+ if (!update.blockable && ret == -EAGAIN)
+ break;
}
up_read(&hmm->mirrors_sem);

@@ -271,6 +268,7 @@ static const struct mmu_notifier_ops hmm_mmu_notifier_ops = {
*
* @mirror: new mirror struct to register
* @mm: mm to register against
+ * Return: 0 on success, -ENOMEM if no memory, -EINVAL if invalid arguments
*
* To start mirroring a process address space, the device driver must register
* an HMM mirror struct.
@@ -298,7 +296,7 @@ EXPORT_SYMBOL(hmm_mirror_register);
/*
* hmm_mirror_unregister() - unregister a mirror
*
- * @mirror: new mirror struct to register
+ * @mirror: mirror struct to unregister
*
* Stop mirroring a process address space, and cleanup.
*/
@@ -372,7 +370,7 @@ static int hmm_pfns_bad(unsigned long addr,
* @fault: should we fault or not ?
* @write_fault: write fault ?
* @walk: mm_walk structure
- * Returns: 0 on success, -EBUSY after page fault, or page fault error
+ * Return: 0 on success, -EBUSY after page fault, or page fault error
*
* This function will be called whenever pmd_none() or pte_none() returns true,
* or whenever there is no page directory covering the virtual address range.
@@ -911,6 +909,7 @@ int hmm_range_register(struct hmm_range *range,
unsigned page_shift)
{
unsigned long mask = ((1UL << page_shift) - 1UL);
+ struct hmm *hmm;

range->valid = false;
range->hmm = NULL;
@@ -924,28 +923,29 @@ int hmm_range_register(struct hmm_range *range,
range->start = start;
range->end = end;

- range->hmm = hmm_get_or_create(mm);
- if (!range->hmm)
+ hmm = hmm_get_or_create(mm);
+ if (!hmm)
return -EFAULT;

/* Check if hmm_mm_destroy() was call. */
- if (range->hmm->mm == NULL || range->hmm->dead) {
- hmm_put(range->hmm);
+ if (hmm->mm == NULL || hmm->dead) {
+ hmm_put(hmm);
return -EFAULT;
}

- /* Initialize range to track CPU page table update */
- mutex_lock(&range->hmm->lock);
+ /* Initialize range to track CPU page table updates. */
+ mutex_lock(&hmm->lock);

- list_add_rcu(&range->list, &range->hmm->ranges);
+ range->hmm = hmm;
+ list_add_rcu(&range->list, &hmm->ranges);

/*
* If there are any concurrent notifiers we have to wait for them for
* the range to be valid (see hmm_range_wait_until_valid()).
*/
- if (!range->hmm->notifiers)
+ if (!hmm->notifiers)
range->valid = true;
- mutex_unlock(&range->hmm->lock);
+ mutex_unlock(&hmm->lock);

return 0;
}
@@ -960,17 +960,19 @@ EXPORT_SYMBOL(hmm_range_register);
*/
void hmm_range_unregister(struct hmm_range *range)
{
+ struct hmm *hmm = range->hmm;
+
/* Sanity check this really should not happen. */
- if (range->hmm == NULL || range->end <= range->start)
+ if (hmm == NULL || range->end <= range->start)
return;

- mutex_lock(&range->hmm->lock);
+ mutex_lock(&hmm->lock);
list_del_rcu(&range->list);
- mutex_unlock(&range->hmm->lock);
+ mutex_unlock(&hmm->lock);

/* Drop reference taken by hmm_range_register() */
range->valid = false;
- hmm_put(range->hmm);
+ hmm_put(hmm);
range->hmm = NULL;
}
EXPORT_SYMBOL(hmm_range_unregister);
@@ -978,7 +980,7 @@ EXPORT_SYMBOL(hmm_range_unregister);
/*
* hmm_range_snapshot() - snapshot CPU page table for a range
* @range: range
- * Returns: -EINVAL if invalid argument, -ENOMEM out of memory, -EPERM invalid
+ * Return: -EINVAL if invalid argument, -ENOMEM out of memory, -EPERM invalid
* permission (for instance asking for write and range is read only),
* -EAGAIN if you need to retry, -EFAULT invalid (ie either no valid
* vma or it is illegal to access that range), number of valid pages
@@ -1061,7 +1063,7 @@ EXPORT_SYMBOL(hmm_range_snapshot);
* hmm_range_fault() - try to fault some address in a virtual address range
* @range: range being faulted
* @block: allow blocking on fault (if true it sleeps and do not drop mmap_sem)
- * Returns: number of valid pages in range->pfns[] (from range start
+ * Return: number of valid pages in range->pfns[] (from range start
* address). This may be zero. If the return value is negative,
* then one of the following values may be returned:
*
@@ -1179,7 +1181,7 @@ EXPORT_SYMBOL(hmm_range_fault);
* @device: device against to dma map page to
* @daddrs: dma address of mapped pages
* @block: allow blocking on fault (if true it sleeps and do not drop mmap_sem)
- * Returns: number of pages mapped on success, -EAGAIN if mmap_sem have been
+ * Return: number of pages mapped on success, -EAGAIN if mmap_sem have been
* drop and you need to try again, some other error value otherwise
*
* Note same usage pattern as hmm_range_fault().
@@ -1267,7 +1269,7 @@ EXPORT_SYMBOL(hmm_range_dma_map);
* @device: device against which dma map was done
* @daddrs: dma address of mapped pages
* @dirty: dirty page if it had the write flag set
- * Returns: number of page unmapped on success, -EINVAL otherwise
+ * Return: number of page unmapped on success, -EINVAL otherwise
*
* Note that caller MUST abide by mmu notifier or use HMM mirror and abide
* to the sync_cpu_device_pagetables() callback so that it is safe here to
@@ -1390,7 +1392,7 @@ static void hmm_devmem_free(struct page *page, void *data)
* @ops: memory event device driver callback (see struct hmm_devmem_ops)
* @device: device struct to bind the resource too
* @size: size in bytes of the device memory to add
- * Returns: pointer to new hmm_devmem struct ERR_PTR otherwise
+ * Return: pointer to new hmm_devmem struct ERR_PTR otherwise
*
* This function first finds an empty range of physical address big enough to
* contain the new resource, and then hotplugs it as ZONE_DEVICE memory, which