zram: factor out ZRAM_SAME write

Handling of ZRAM_SAME now uses a goto to the final stages of
zram_write_page() plus it introduces a branch and flags variable, which is
not making the code any simpler.  In reality, we can handle ZRAM_SAME
immediately when we detect such pages and remove a goto and a branch.

Factor out ZRAM_SAME handling into a separate routine to simplify
zram_write_page().

Link: https://lkml.kernel.org/r/20241218063513.297475-4-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

drivers/block/zram/zram_drv.c

@@ -1625,6 +1625,20 @@ static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
 	return zram_read_page(zram, bvec->bv_page, index, bio);
 }
 
+static int write_same_filled_page(struct zram *zram, unsigned long fill,
+				  u32 index)
+{
+	zram_slot_lock(zram, index);
+	zram_set_flag(zram, index, ZRAM_SAME);
+	zram_set_handle(zram, index, fill);
+	zram_slot_unlock(zram, index);
+
+	atomic64_inc(&zram->stats.same_pages);
+	atomic64_inc(&zram->stats.pages_stored);
+
+	return 0;
+}
+
 static int zram_write_page(struct zram *zram, struct page *page, u32 index)
 {
 	int ret = 0;
@@ -1634,22 +1648,18 @@ static int zram_write_page(struct zram *zram, struct page *page, u32 index)
 	void *src, *dst, *mem;
 	struct zcomp_strm *zstrm;
 	unsigned long element = 0;
-	enum zram_pageflags flags = 0;
+	bool same_filled;
 
 	/* First, free memory allocated to this slot (if any) */
 	zram_slot_lock(zram, index);
 	zram_free_page(zram, index);
 	zram_slot_unlock(zram, index);
 
 	mem = kmap_local_page(page);
-	if (page_same_filled(mem, &element)) {
-		kunmap_local(mem);
-		/* Free memory associated with this sector now. */
-		flags = ZRAM_SAME;
-		atomic64_inc(&zram->stats.same_pages);
-		goto out;
-	}
+	same_filled = page_same_filled(mem, &element);
 	kunmap_local(mem);
+	if (same_filled)
+		return write_same_filled_page(zram, element, index);
 
 compress_again:
 	zstrm = zcomp_stream_get(zram->comps[ZRAM_PRIMARY_COMP]);
@@ -1728,21 +1738,16 @@ static int zram_write_page(struct zram *zram, struct page *page, u32 index)
 	zcomp_stream_put(zram->comps[ZRAM_PRIMARY_COMP]);
 	zs_unmap_object(zram->mem_pool, handle);
 	atomic64_add(comp_len, &zram->stats.compr_data_size);
-out:
+
 	zram_slot_lock(zram, index);
 	if (comp_len == PAGE_SIZE) {
 		zram_set_flag(zram, index, ZRAM_HUGE);
 		atomic64_inc(&zram->stats.huge_pages);
 		atomic64_inc(&zram->stats.huge_pages_since);
 	}
 
-	if (flags) {
-		zram_set_flag(zram, index, flags);
-		zram_set_handle(zram, index, element);
-	}  else {
-		zram_set_handle(zram, index, handle);
-		zram_set_obj_size(zram, index, comp_len);
-	}
+	zram_set_handle(zram, index, handle);
+	zram_set_obj_size(zram, index, comp_len);
 	zram_slot_unlock(zram, index);
 
 	/* Update stats */