File 1005-drm-i915-Use-pagecache-write-to-prepopulate-shmemfs-.patch of Package drm
From 4e6fdafa7ac395ad47a80a0e7b4fd1e11550f862 Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Tue, 7 Mar 2017 12:03:38 +0000
Subject: [PATCH] drm/i915: Use pagecache write to prepopulate shmemfs from pwrite-ioctl
Git-commit: 4e6fdafa7ac395ad47a80a0e7b4fd1e11550f862
Patch-mainline: 4.11-rc3
References: bsc#1040463
Before we instantiate/pin the backing store for our use, we
can prepopulate the shmemfs filp efficiently using a write into the
pagecache. We avoid the penalty of instantiating all the pages, important
if the user is just writing to a few and never uses the object on the GPU,
and using a direct write into shmemfs allows it to avoid the cost of
retrieving a page (mostly the clear-before-use, but in theory we could
curtail swapin) before it is overwritten.
This can be extended later to provide additional specialisation for
other backends (other than shmemfs). For now it provides a defense
against very large write-only allocations from exhausting all of system
memory.
V2: Smelling fixes.
Fixes: fe115628d567 ("drm/i915: Implement pwrite without struct-mutex")
References: https://bugs.freedesktop.org/show_bug.cgi?id=99107
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.william.auld@gmail.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: <stable@vger.kernel.org> # v4.10+
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170307120338.7277-2-chris@chris-wilson.co.uk
(cherry picked from commit 7c55e2c5772dcf3cbacd0fa2bcfeefae416b73f7)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
drivers/gpu/drm/i915/i915_drv.h | 2 +
drivers/gpu/drm/i915/i915_gem.c | 79 ++++++++++++++++++++++++++++++++++++++++
2 files changed, 81 insertions(+)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1460,6 +1460,12 @@ i915_gem_pwrite_ioctl(struct drm_device
if (ret)
goto err_rpm;
+ ret = -ENODEV;
+ if (obj->ops->pwrite)
+ ret = obj->ops->pwrite(obj, args);
+ if (ret != -ENODEV)
+ goto err_unlock;
+
ret = -EFAULT;
/* We can only do the GTT pwrite on untiled buffers, as otherwise
* it would end up going through the fenced access, and we'll get
@@ -1488,6 +1494,8 @@ i915_gem_pwrite_ioctl(struct drm_device
return ret;
+err_unlock:
+ mutex_unlock(&dev->struct_mutex);
err_rpm:
intel_runtime_pm_put(dev_priv);
err:
@@ -2369,6 +2377,75 @@ i915_gem_object_get_pages(struct drm_i91
return 0;
}
+static int
+i915_gem_object_pwrite_gtt(struct drm_i915_gem_object *obj,
+ const struct drm_i915_gem_pwrite *arg)
+{
+ struct address_space *mapping = obj->base.filp->f_mapping;
+ char __user *user_data = (char __user *)(uintptr_t)arg->data_ptr;
+ u64 remain, offset;
+ unsigned int pg;
+
+ /* Before we instantiate/pin the backing store for our use, we
+ * can prepopulate the shmemfs filp efficiently using a write into
+ * the pagecache. We avoid the penalty of instantiating all the
+ * pages, important if the user is just writing to a few and never
+ * uses the object on the GPU, and using a direct write into shmemfs
+ * allows it to avoid the cost of retrieving a page (either swapin
+ * or clearing-before-use) before it is overwritten.
+ */
+ if (READ_ONCE(obj->pages))
+ return -ENODEV;
+
+ /* Before the pages are instantiated the object is treated as being
+ * in the CPU domain. The pages will be clflushed as required before
+ * use, and we can freely write into the pages directly. If userspace
+ * races pwrite with any other operation; corruption will ensue -
+ * that is userspace's prerogative!
+ */
+
+ remain = arg->size;
+ offset = arg->offset;
+ pg = offset_in_page(offset);
+
+ do {
+ unsigned int len, unwritten;
+ struct page *page;
+ void *data, *vaddr;
+ int err;
+
+ len = PAGE_SIZE - pg;
+ if (len > remain)
+ len = remain;
+
+ err = pagecache_write_begin(obj->base.filp, mapping,
+ offset, len, 0,
+ &page, &data);
+ if (err < 0)
+ return err;
+
+ vaddr = kmap(page);
+ unwritten = copy_from_user(vaddr + pg, user_data, len);
+ kunmap(page);
+
+ err = pagecache_write_end(obj->base.filp, mapping,
+ offset, len, len - unwritten,
+ page, data);
+ if (err < 0)
+ return err;
+
+ if (unwritten)
+ return -EFAULT;
+
+ remain -= len;
+ user_data += len;
+ offset += len;
+ pg = 0;
+ } while (remain);
+
+ return 0;
+}
+
/* The 'mapping' part of i915_gem_object_pin_map() below */
static void *i915_gem_object_map(const struct drm_i915_gem_object *obj,
enum i915_map_type type)
@@ -4099,6 +4176,8 @@ static const struct drm_i915_gem_object_
.flags = I915_GEM_OBJECT_HAS_STRUCT_PAGE,
.get_pages = i915_gem_object_get_pages_gtt,
.put_pages = i915_gem_object_put_pages_gtt,
+
+ .pwrite = i915_gem_object_pwrite_gtt,
};
struct drm_i915_gem_object *i915_gem_object_create(struct drm_device *dev,
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2161,6 +2161,8 @@ struct drm_i915_gem_object_ops {
int (*get_pages)(struct drm_i915_gem_object *);
void (*put_pages)(struct drm_i915_gem_object *);
+ int (*pwrite)(struct drm_i915_gem_object *,
+ const struct drm_i915_gem_pwrite *);
int (*dmabuf_export)(struct drm_i915_gem_object *);
void (*release)(struct drm_i915_gem_object *);
};
