drm/i915/gem: Drop relocation slowpath
Since the relocations are no longer performed under a global struct_mutex, or any other lock, that is also held by pagefault handlers, we can relax and allow our fast path to take a fault. As we no longer need to abort the fast path for lock avoidance, we no longer need the slow path handling at all. Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Reviewed-by: Matthew Auld <matthew.auld@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20200311160310.26711-1-chris@chris-wilson.co.uk
This commit is contained in:
Chris Wilson
parent
07bcfd1291
commit
7dc8f11437
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@ -1440,9 +1440,7 @@ static int eb_relocate_vma(struct i915_execbuffer *eb, struct eb_vma *ev)
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* we would try to acquire the struct mutex again. Obviously
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* this is bad and so lockdep complains vehemently.
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*/
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pagefault_disable();
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copied = __copy_from_user_inatomic(r, urelocs, count * sizeof(r[0]));
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pagefault_enable();
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copied = __copy_from_user(r, urelocs, count * sizeof(r[0]));
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if (unlikely(copied)) {
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remain = -EFAULT;
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goto out;
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@ -1492,236 +1490,6 @@ out:
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return remain;
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}
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static int
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eb_relocate_vma_slow(struct i915_execbuffer *eb, struct eb_vma *ev)
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{
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const struct drm_i915_gem_exec_object2 *entry = ev->exec;
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struct drm_i915_gem_relocation_entry *relocs =
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u64_to_ptr(typeof(*relocs), entry->relocs_ptr);
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unsigned int i;
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int err;
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for (i = 0; i < entry->relocation_count; i++) {
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u64 offset = eb_relocate_entry(eb, ev, &relocs[i]);
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if ((s64)offset < 0) {
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err = (int)offset;
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goto err;
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}
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}
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err = 0;
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err:
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reloc_cache_reset(&eb->reloc_cache);
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return err;
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}
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static int check_relocations(const struct drm_i915_gem_exec_object2 *entry)
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{
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const char __user *addr, *end;
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unsigned long size;
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char __maybe_unused c;
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size = entry->relocation_count;
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if (size == 0)
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return 0;
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if (size > N_RELOC(ULONG_MAX))
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return -EINVAL;
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addr = u64_to_user_ptr(entry->relocs_ptr);
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size *= sizeof(struct drm_i915_gem_relocation_entry);
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if (!access_ok(addr, size))
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return -EFAULT;
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end = addr + size;
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for (; addr < end; addr += PAGE_SIZE) {
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int err = __get_user(c, addr);
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if (err)
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return err;
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}
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return __get_user(c, end - 1);
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}
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static int eb_copy_relocations(const struct i915_execbuffer *eb)
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{
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struct drm_i915_gem_relocation_entry *relocs;
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const unsigned int count = eb->buffer_count;
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unsigned int i;
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int err;
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for (i = 0; i < count; i++) {
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const unsigned int nreloc = eb->exec[i].relocation_count;
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struct drm_i915_gem_relocation_entry __user *urelocs;
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unsigned long size;
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unsigned long copied;
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if (nreloc == 0)
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continue;
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err = check_relocations(&eb->exec[i]);
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if (err)
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goto err;
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urelocs = u64_to_user_ptr(eb->exec[i].relocs_ptr);
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size = nreloc * sizeof(*relocs);
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relocs = kvmalloc_array(size, 1, GFP_KERNEL);
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if (!relocs) {
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err = -ENOMEM;
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goto err;
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}
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/* copy_from_user is limited to < 4GiB */
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copied = 0;
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do {
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unsigned int len =
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min_t(u64, BIT_ULL(31), size - copied);
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if (__copy_from_user((char *)relocs + copied,
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(char __user *)urelocs + copied,
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len))
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goto end;
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copied += len;
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} while (copied < size);
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/*
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* As we do not update the known relocation offsets after
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* relocating (due to the complexities in lock handling),
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* we need to mark them as invalid now so that we force the
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* relocation processing next time. Just in case the target
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* object is evicted and then rebound into its old
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* presumed_offset before the next execbuffer - if that
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* happened we would make the mistake of assuming that the
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* relocations were valid.
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*/
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if (!user_access_begin(urelocs, size))
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goto end;
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for (copied = 0; copied < nreloc; copied++)
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unsafe_put_user(-1,
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&urelocs[copied].presumed_offset,
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end_user);
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user_access_end();
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eb->exec[i].relocs_ptr = (uintptr_t)relocs;
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}
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return 0;
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end_user:
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user_access_end();
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end:
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kvfree(relocs);
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err = -EFAULT;
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err:
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while (i--) {
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relocs = u64_to_ptr(typeof(*relocs), eb->exec[i].relocs_ptr);
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if (eb->exec[i].relocation_count)
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kvfree(relocs);
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}
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return err;
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}
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static int eb_prefault_relocations(const struct i915_execbuffer *eb)
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{
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const unsigned int count = eb->buffer_count;
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unsigned int i;
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for (i = 0; i < count; i++) {
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int err;
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err = check_relocations(&eb->exec[i]);
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if (err)
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return err;
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}
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return 0;
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}
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static noinline int eb_relocate_slow(struct i915_execbuffer *eb)
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{
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bool have_copy = false;
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struct eb_vma *ev;
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int err = 0;
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repeat:
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if (signal_pending(current)) {
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err = -ERESTARTSYS;
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goto out;
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}
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/*
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* We take 3 passes through the slowpatch.
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*
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* 1 - we try to just prefault all the user relocation entries and
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* then attempt to reuse the atomic pagefault disabled fast path again.
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*
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* 2 - we copy the user entries to a local buffer here outside of the
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* local and allow ourselves to wait upon any rendering before
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* relocations
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*
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* 3 - we already have a local copy of the relocation entries, but
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* were interrupted (EAGAIN) whilst waiting for the objects, try again.
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*/
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if (!err) {
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err = eb_prefault_relocations(eb);
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} else if (!have_copy) {
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err = eb_copy_relocations(eb);
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have_copy = err == 0;
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} else {
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cond_resched();
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err = 0;
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}
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if (err)
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goto out;
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list_for_each_entry(ev, &eb->relocs, reloc_link) {
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if (!have_copy) {
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pagefault_disable();
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err = eb_relocate_vma(eb, ev);
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pagefault_enable();
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if (err)
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goto repeat;
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} else {
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err = eb_relocate_vma_slow(eb, ev);
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if (err)
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goto err;
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}
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}
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/*
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* Leave the user relocations as are, this is the painfully slow path,
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* and we want to avoid the complication of dropping the lock whilst
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* having buffers reserved in the aperture and so causing spurious
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* ENOSPC for random operations.
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*/
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err:
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if (err == -EAGAIN)
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goto repeat;
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out:
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if (have_copy) {
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const unsigned int count = eb->buffer_count;
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unsigned int i;
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for (i = 0; i < count; i++) {
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const struct drm_i915_gem_exec_object2 *entry =
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&eb->exec[i];
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struct drm_i915_gem_relocation_entry *relocs;
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if (!entry->relocation_count)
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continue;
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relocs = u64_to_ptr(typeof(*relocs), entry->relocs_ptr);
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kvfree(relocs);
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}
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}
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return err;
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}
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static int eb_relocate(struct i915_execbuffer *eb)
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{
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int err;
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@ -1743,8 +1511,9 @@ static int eb_relocate(struct i915_execbuffer *eb)
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struct eb_vma *ev;
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list_for_each_entry(ev, &eb->relocs, reloc_link) {
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if (eb_relocate_vma(eb, ev))
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return eb_relocate_slow(eb);
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err = eb_relocate_vma(eb, ev);
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if (err)
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return err;
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}
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}
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