drm/i915: Report -EFAULT before pwrite fast path into shmemfs

When pwriting into shmemfs, the fast path pagecache_write does not
notice when it is writing to beyond the end of the truncated shmemfs
inode. Report -EFAULT directly when we try to use pwrite into the
!I915_MADV_WILLNEED object.

Fixes: 7c55e2c5772d ("drm/i915: Use pagecache write to prepopulate shmemfs from pwrite-ioctl")
Testcase: igt/gem_madvise/dontneed-before-pwrite
Signed-off-by: Chris Wilson <[email protected]>
Cc: Matthew Auld <[email protected]>
Cc: Joonas Lahtinen <[email protected]>
Cc: Mika Kuoppala <[email protected]>
Reviewed-by: Joonas Lahtinen <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
(cherry picked from commit a6d65e451cc4e7127698384868a4447ee7be7d16)
Signed-off-by: Rodrigo Vivi <[email protected]>

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index af289d35b77a249c8fa9a7aab4a9672592399d51..32e857dc507cf9b1a9247f3bab497616d82e60a9 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2657,6 +2657,9 @@ i915_gem_object_pwrite_gtt(struct drm_i915_gem_object *obj,
        if (READ_ONCE(obj->mm.pages))
                return -ENODEV;
 
+       if (obj->mm.madv != I915_MADV_WILLNEED)
+               return -EFAULT;
+
        /* 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