[PATCH v5 5/6] drm/i915/gem: Read and shrink memory in a separate function

Continue unloading shmem_sg_alloc_table by placing reading
folios and shrink call into a new helper.
Make the code more reader-friendly by removing two iteration
loop over a structure and replacing it with instruction
sequence.

Signed-off-by: Krzysztof Karas <[email protected]>
---
 drivers/gpu/drm/i915/gem/i915_gem_shmem.c | 103 ++++++++++++----------
 1 file changed, 56 insertions(+), 47 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
index b63a9395306d..a8ffcfc0017b 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
@@ -79,6 +79,56 @@ static int set_page_count_from_size(size_t size, unsigned int *page_count,
 	return 0;
 }
 
+static struct folio *shmem_shrink_get_folio(struct address_space *mapping,
+					    unsigned long folio_index,
+					    gfp_t gfp, unsigned int page_count,
+					    struct drm_i915_private *i915)
+{
+	struct folio *folio = NULL;
+
+	cond_resched();
+	folio = shmem_read_folio_gfp(mapping, folio_index, gfp);
+	if (IS_ERR(folio)) {
+		i915_gem_shrink(NULL, i915, 2 * page_count, NULL,
+				I915_SHRINK_BOUND | I915_SHRINK_UNBOUND);
+
+		/*
+		 * We've tried hard to allocate the memory by reaping
+		 * our own buffer, now let the real VM do its job and
+		 * go down in flames if truly OOM.
+		 *
+		 * However, since graphics tend to be disposable,
+		 * defer the oom here by reporting the ENOMEM back
+		 * to userspace.
+		 *
+		 * Reclaim and warn, but no oom.
+		 */
+		gfp = mapping_gfp_mask(mapping);
+
+		/*
+		 * Our bo are always dirty and so we require
+		 * kswapd to reclaim our pages (direct reclaim
+		 * does not effectively begin pageout of our
+		 * buffers on its own). However, direct reclaim
+		 * only waits for kswapd when under allocation
+		 * congestion. So as a result __GFP_RECLAIM is
+		 * unreliable and fails to actually reclaim our
+		 * dirty pages -- unless you try over and over
+		 * again with !__GFP_NORETRY. However, we still
+		 * want to fail this allocation rather than
+		 * trigger the out-of-memory killer and for
+		 * this we want __GFP_RETRY_MAYFAIL.
+		 */
+		gfp |= __GFP_RETRY_MAYFAIL | __GFP_NOWARN;
+
+		/* Retry once after shrinking and gfp modification. */
+		cond_resched();
+		folio = shmem_read_folio_gfp(mapping, folio_index, gfp);
+	}
+
+	return folio;
+}
+
 int shmem_sg_alloc_table(struct drm_i915_private *i915, struct sg_table *st,
 			 size_t size, struct intel_memory_region *mr,
 			 struct address_space *mapping,
@@ -119,57 +169,16 @@ int shmem_sg_alloc_table(struct drm_i915_private *i915, struct sg_table *st,
 	for (i = 0; i < page_count; i++) {
 		unsigned long folio_page_index = 0;
 		unsigned long nr_pages;
-		const unsigned int shrink[] = {
-			I915_SHRINK_BOUND | I915_SHRINK_UNBOUND,
-			0,
-		}, *s = shrink;
 		gfp_t gfp = noreclaim;
 
 		/* Grab the next folio if we exhausted the current one. */
 		if (!i || i > folio_end) {
-			do {
-				cond_resched();
-				folio = shmem_read_folio_gfp(mapping, i, gfp);
-				if (!IS_ERR(folio))
-					break;
-
-				if (!*s) {
-					ret = PTR_ERR(folio);
-					goto err_sg;
-				}
-
-				i915_gem_shrink(NULL, i915, 2 * page_count, NULL, *s++);
-
-				/*
-				 * We've tried hard to allocate the memory by reaping
-				 * our own buffer, now let the real VM do its job and
-				 * go down in flames if truly OOM.
-				 *
-				 * However, since graphics tend to be disposable,
-				 * defer the oom here by reporting the ENOMEM back
-				 * to userspace.
-				 */
-				if (!*s) {
-					/* reclaim and warn, but no oom */
-					gfp = mapping_gfp_mask(mapping);
-
-					/*
-					 * Our bo are always dirty and so we require
-					 * kswapd to reclaim our pages (direct reclaim
-					 * does not effectively begin pageout of our
-					 * buffers on its own). However, direct reclaim
-					 * only waits for kswapd when under allocation
-					 * congestion. So as a result __GFP_RECLAIM is
-					 * unreliable and fails to actually reclaim our
-					 * dirty pages -- unless you try over and over
-					 * again with !__GFP_NORETRY. However, we still
-					 * want to fail this allocation rather than
-					 * trigger the out-of-memory killer and for
-					 * this we want __GFP_RETRY_MAYFAIL.
-					 */
-					gfp |= __GFP_RETRY_MAYFAIL | __GFP_NOWARN;
-				}
-			} while (1);
+			folio = shmem_shrink_get_folio(mapping, i, gfp,
+						       page_count, i915);
+			if (IS_ERR(folio)) {
+				ret = PTR_ERR(folio);
+				goto err_sg;
+			}
 
 			folio_start = folio_pgoff(folio);
 			folio_end = folio_start + folio_nr_pages(folio) - 1;
-- 
2.34.1