[PATCH] gpu: drm: omapdrm: Adding new typedef vm_fault_t

[PATCH] gpu: drm: omapdrm: Adding new typedef vm_fault_t

[Souptick Joarder]

Use new return type vm_fault_t for fault handler. For
now, this is just documenting that the function returns
a VM_FAULT value rather than an errno. Once all instances
are converted, vm_fault_t will become a distinct type.

Ref-> commit 1c8f422059ae ("mm: change return type to vm_fault_t")

Previously vm_insert_mixed() returns err which driver
mapped into VM_FAULT_* type. Also return value of
vm_insert_mixed() not handled correctly and 0 was
returned inside fault_2d() as default. The new function
vmf_insert_mixed() will replace this inefficiency by
returning correct VM_FAULT_* type.

vmf_error() is the newly introduce inline function
in 4.17-rc6.

Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
Reviewed-by: Matthew Wilcox <mawilcox@microsoft.com>
---
 drivers/gpu/drm/omapdrm/omap_gem.c | 51 +++++++++++++++++---------------------
 drivers/gpu/drm/omapdrm/omap_gem.h |  3 ++-
 2 files changed, 25 insertions(+), 29 deletions(-)

diff --git a/drivers/gpu/drm/omapdrm/omap_gem.c b/drivers/gpu/drm/omapdrm/omap_gem.c
index 0faf042..f9fe755 100644
--- a/drivers/gpu/drm/omapdrm/omap_gem.c
+++ b/drivers/gpu/drm/omapdrm/omap_gem.c
@@ -371,7 +371,7 @@ size_t omap_gem_mmap_size(struct drm_gem_object *obj)
  */
 
 /* Normal handling for the case of faulting in non-tiled buffers */
-static int fault_1d(struct drm_gem_object *obj,
+static vm_fault_t fault_1d(struct drm_gem_object *obj,
 		struct vm_area_struct *vma, struct vm_fault *vmf)
 {
 	struct omap_gem_object *omap_obj = to_omap_bo(obj);
@@ -392,11 +392,12 @@ static int fault_1d(struct drm_gem_object *obj,
 	VERB("Inserting %p pfn %lx, pa %lx", (void *)vmf->address,
 			pfn, pfn << PAGE_SHIFT);
 
-	return vm_insert_mixed(vma, vmf->address, __pfn_to_pfn_t(pfn, PFN_DEV));
+	return vmf_insert_mixed(vma, vmf->address,
+			__pfn_to_pfn_t(pfn, PFN_DEV));
 }
 
 /* Special handling for the case of faulting in 2d tiled buffers */
-static int fault_2d(struct drm_gem_object *obj,
+static vm_fault_t fault_2d(struct drm_gem_object *obj,
 		struct vm_area_struct *vma, struct vm_fault *vmf)
 {
 	struct omap_gem_object *omap_obj = to_omap_bo(obj);
@@ -407,7 +408,8 @@ static int fault_2d(struct drm_gem_object *obj,
 	unsigned long pfn;
 	pgoff_t pgoff, base_pgoff;
 	unsigned long vaddr;
-	int i, ret, slots;
+	int i, err, slots;
+	vm_fault_t ret;
 
 	/*
 	 * Note the height of the slot is also equal to the number of pages
@@ -473,9 +475,10 @@ static int fault_2d(struct drm_gem_object *obj,
 	memset(pages + slots, 0,
 			sizeof(struct page *) * (n - slots));
 
-	ret = tiler_pin(entry->block, pages, ARRAY_SIZE(pages), 0, true);
-	if (ret) {
-		dev_err(obj->dev->dev, "failed to pin: %d\n", ret);
+	err = tiler_pin(entry->block, pages, ARRAY_SIZE(pages), 0, true);
+	if (err) {
+		ret = vmf_error(err);
+		dev_err(obj->dev->dev, "failed to pin: %d\n", err);
 		return ret;
 	}
 
@@ -485,7 +488,10 @@ static int fault_2d(struct drm_gem_object *obj,
 			pfn, pfn << PAGE_SHIFT);
 
 	for (i = n; i > 0; i--) {
-		vm_insert_mixed(vma, vaddr, __pfn_to_pfn_t(pfn, PFN_DEV));
+		ret = vmf_insert_mixed(vma,
+			vaddr, __pfn_to_pfn_t(pfn, PFN_DEV));
+		if (ret & VM_FAULT_ERROR)
+			break;
 		pfn += priv->usergart[fmt].stride_pfn;
 		vaddr += PAGE_SIZE * m;
 	}
@@ -494,7 +500,7 @@ static int fault_2d(struct drm_gem_object *obj,
 	priv->usergart[fmt].last = (priv->usergart[fmt].last + 1)
 				 % NUM_USERGART_ENTRIES;
 
-	return 0;
+	return ret;
 }
 
 /**
@@ -509,14 +515,15 @@ static int fault_2d(struct drm_gem_object *obj,
  * vma->vm_private_data points to the GEM object that is backing this
  * mapping.
  */
-int omap_gem_fault(struct vm_fault *vmf)
+vm_fault_t omap_gem_fault(struct vm_fault *vmf)
 {
 	struct vm_area_struct *vma = vmf->vma;
 	struct drm_gem_object *obj = vma->vm_private_data;
 	struct omap_gem_object *omap_obj = to_omap_bo(obj);
 	struct drm_device *dev = obj->dev;
 	struct page **pages;
-	int ret;
+	int err;
+	vm_fault_t ret;
 
 	/* Make sure we don't parallel update on a fault, nor move or remove
 	 * something from beneath our feet
@@ -524,9 +531,11 @@ int omap_gem_fault(struct vm_fault *vmf)
 	mutex_lock(&dev->struct_mutex);
 
 	/* if a shmem backed object, make sure we have pages attached now */
-	ret = get_pages(obj, &pages);
-	if (ret)
+	err = get_pages(obj, &pages);
+	if (err) {
+		ret = vmf_error(err);
 		goto fail;
+	}
 
 	/* where should we do corresponding put_pages().. we are mapping
 	 * the original page, rather than thru a GART, so we can't rely
@@ -542,21 +551,7 @@ int omap_gem_fault(struct vm_fault *vmf)
 
 fail:
 	mutex_unlock(&dev->struct_mutex);
-	switch (ret) {
-	case 0:
-	case -ERESTARTSYS:
-	case -EINTR:
-	case -EBUSY:
-		/*
-		 * EBUSY is ok: this just means that another thread
-		 * already did the job.
-		 */
-		return VM_FAULT_NOPAGE;
-	case -ENOMEM:
-		return VM_FAULT_OOM;
-	default:
-		return VM_FAULT_SIGBUS;
-	}
+	return ret;
 }
 
 /** We override mainly to fix up some of the vm mapping flags.. */
diff --git a/drivers/gpu/drm/omapdrm/omap_gem.h b/drivers/gpu/drm/omapdrm/omap_gem.h
index a78bde0..c1c45fb 100644
--- a/drivers/gpu/drm/omapdrm/omap_gem.h
+++ b/drivers/gpu/drm/omapdrm/omap_gem.h
@@ -21,6 +21,7 @@
 #define __OMAPDRM_GEM_H__
 
 #include <linux/types.h>
+#include <linux/mm_types.h>
 
 enum dma_data_direction;
 
@@ -80,7 +81,7 @@ struct dma_buf *omap_gem_prime_export(struct drm_device *dev,
 struct drm_gem_object *omap_gem_prime_import(struct drm_device *dev,
 		struct dma_buf *buffer);
 
-int omap_gem_fault(struct vm_fault *vmf);
+vm_fault_t omap_gem_fault(struct vm_fault *vmf);
 int omap_gem_roll(struct drm_gem_object *obj, u32 roll);
 void omap_gem_cpu_sync_page(struct drm_gem_object *obj, int pgoff);
 void omap_gem_dma_sync_buffer(struct drm_gem_object *obj,
-- 
1.9.1

Re: [PATCH] gpu: drm: omapdrm: Adding new typedef vm_fault_t

[kbuild test robot]

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Hi Souptick,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on drm/drm-next]
[also build test WARNING on v4.17-rc6 next-20180517]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Souptick-Joarder/gpu-drm-omapdrm-Adding-new-typedef-vm_fault_t/20180522-135920
base:   git://people.freedesktop.org/~airlied/linux.git drm-next
config: arm-omap2plus_defconfig (attached as .config)
compiler: arm-linux-gnueabi-gcc (Debian 7.2.0-11) 7.2.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        make.cross ARCH=arm 

Note: it may well be a FALSE warning. FWIW you are at least aware of it now.
http://gcc.gnu.org/wiki/Better_Uninitialized_Warnings

All warnings (new ones prefixed by >>):

   drivers/gpu//drm/omapdrm/omap_gem.c: In function 'fault_2d':
   drivers/gpu//drm/omapdrm/omap_gem.c:480:9: error: implicit declaration of function 'vmf_error'; did you mean '__pmd_error'? [-Werror=implicit-function-declaration]
      ret = vmf_error(err);
            ^~~~~~~~~
            __pmd_error
>> drivers/gpu//drm/omapdrm/omap_gem.c:503:9: warning: 'ret' may be used uninitialized in this function [-Wmaybe-uninitialized]
     return ret;
            ^~~
   cc1: some warnings being treated as errors

vim +/ret +503 drivers/gpu//drm/omapdrm/omap_gem.c

   398	
   399	/* Special handling for the case of faulting in 2d tiled buffers */
   400	static vm_fault_t fault_2d(struct drm_gem_object *obj,
   401			struct vm_area_struct *vma, struct vm_fault *vmf)
   402	{
   403		struct omap_gem_object *omap_obj = to_omap_bo(obj);
   404		struct omap_drm_private *priv = obj->dev->dev_private;
   405		struct omap_drm_usergart_entry *entry;
   406		enum tiler_fmt fmt = gem2fmt(omap_obj->flags);
   407		struct page *pages[64];  /* XXX is this too much to have on stack? */
   408		unsigned long pfn;
   409		pgoff_t pgoff, base_pgoff;
   410		unsigned long vaddr;
   411		int i, err, slots;
   412		vm_fault_t ret;
   413	
   414		/*
   415		 * Note the height of the slot is also equal to the number of pages
   416		 * that need to be mapped in to fill 4kb wide CPU page.  If the slot
   417		 * height is 64, then 64 pages fill a 4kb wide by 64 row region.
   418		 */
   419		const int n = priv->usergart[fmt].height;
   420		const int n_shift = priv->usergart[fmt].height_shift;
   421	
   422		/*
   423		 * If buffer width in bytes > PAGE_SIZE then the virtual stride is
   424		 * rounded up to next multiple of PAGE_SIZE.. this need to be taken
   425		 * into account in some of the math, so figure out virtual stride
   426		 * in pages
   427		 */
   428		const int m = DIV_ROUND_UP(omap_obj->width << fmt, PAGE_SIZE);
   429	
   430		/* We don't use vmf->pgoff since that has the fake offset: */
   431		pgoff = (vmf->address - vma->vm_start) >> PAGE_SHIFT;
   432	
   433		/*
   434		 * Actual address we start mapping at is rounded down to previous slot
   435		 * boundary in the y direction:
   436		 */
   437		base_pgoff = round_down(pgoff, m << n_shift);
   438	
   439		/* figure out buffer width in slots */
   440		slots = omap_obj->width >> priv->usergart[fmt].slot_shift;
   441	
   442		vaddr = vmf->address - ((pgoff - base_pgoff) << PAGE_SHIFT);
   443	
   444		entry = &priv->usergart[fmt].entry[priv->usergart[fmt].last];
   445	
   446		/* evict previous buffer using this usergart entry, if any: */
   447		if (entry->obj)
   448			evict_entry(entry->obj, fmt, entry);
   449	
   450		entry->obj = obj;
   451		entry->obj_pgoff = base_pgoff;
   452	
   453		/* now convert base_pgoff to phys offset from virt offset: */
   454		base_pgoff = (base_pgoff >> n_shift) * slots;
   455	
   456		/* for wider-than 4k.. figure out which part of the slot-row we want: */
   457		if (m > 1) {
   458			int off = pgoff % m;
   459			entry->obj_pgoff += off;
   460			base_pgoff /= m;
   461			slots = min(slots - (off << n_shift), n);
   462			base_pgoff += off << n_shift;
   463			vaddr += off << PAGE_SHIFT;
   464		}
   465	
   466		/*
   467		 * Map in pages. Beyond the valid pixel part of the buffer, we set
   468		 * pages[i] to NULL to get a dummy page mapped in.. if someone
   469		 * reads/writes it they will get random/undefined content, but at
   470		 * least it won't be corrupting whatever other random page used to
   471		 * be mapped in, or other undefined behavior.
   472		 */
   473		memcpy(pages, &omap_obj->pages[base_pgoff],
   474				sizeof(struct page *) * slots);
   475		memset(pages + slots, 0,
   476				sizeof(struct page *) * (n - slots));
   477	
   478		err = tiler_pin(entry->block, pages, ARRAY_SIZE(pages), 0, true);
   479		if (err) {
 > 480			ret = vmf_error(err);
   481			dev_err(obj->dev->dev, "failed to pin: %d\n", err);
   482			return ret;
   483		}
   484	
   485		pfn = entry->dma_addr >> PAGE_SHIFT;
   486	
   487		VERB("Inserting %p pfn %lx, pa %lx", (void *)vmf->address,
   488				pfn, pfn << PAGE_SHIFT);
   489	
   490		for (i = n; i > 0; i--) {
   491			ret = vmf_insert_mixed(vma,
   492				vaddr, __pfn_to_pfn_t(pfn, PFN_DEV));
   493			if (ret & VM_FAULT_ERROR)
   494				break;
   495			pfn += priv->usergart[fmt].stride_pfn;
   496			vaddr += PAGE_SIZE * m;
   497		}
   498	
   499		/* simple round-robin: */
   500		priv->usergart[fmt].last = (priv->usergart[fmt].last + 1)
   501					 % NUM_USERGART_ENTRIES;
   502	
 > 503		return ret;
   504	}
   505	

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

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Re: [PATCH] gpu: drm: omapdrm: Adding new typedef vm_fault_t

[Souptick Joarder]

>    drivers/gpu//drm/omapdrm/omap_gem.c: In function 'fault_2d':
>    drivers/gpu//drm/omapdrm/omap_gem.c:480:9: error: implicit declaration of function 'vmf_error'; did you mean '__pmd_error'? [-Werror=implicit-function-declaration]
>       ret = vmf_error(err);

I think, drm-next and next-20180517 tree doesn't have vmf_error() included.
As of now it's only available in 4.17-rc6.

>             ^~~~~~~~~
>             __pmd_error
>>> drivers/gpu//drm/omapdrm/omap_gem.c:503:9: warning: 'ret' may be used uninitialized in this function [-Wmaybe-uninitialized]
>      return ret;
>             ^~~
>    cc1: some warnings being treated as errors
>

I will fix this in v2.