Staging: zram: Refactor zram_read/write() functions

This patch refactor the code of zram_read/write() functions. It does
not removes a lot of duplicate code alone, but is mostly a helper for
the third patch of this series (Staging: zram: allow partial page
operations).
Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/zram/zram_drv.c

@@ -203,17 +203,9 @@ static void handle_uncompressed_page(struct zram *zram,
 	flush_dcache_page(page);
 }
 
-static void zram_read(struct zram *zram, struct bio *bio)
+static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
+			  u32 index, struct bio *bio)
 {
-
-	int i;
-	u32 index;
-	struct bio_vec *bvec;
-
-	zram_stat64_inc(zram, &zram->stats.num_reads);
-	index = bio->bi_sector >> SECTORS_PER_PAGE_SHIFT;
-
-	bio_for_each_segment(bvec, bio, i) {
 	int ret;
 	size_t clen;
 	struct page *page;
@@ -224,8 +216,7 @@ static void zram_read(struct zram *zram, struct bio *bio)
 
 	if (zram_test_flag(zram, index, ZRAM_ZERO)) {
 		handle_zero_page(page);
-			index++;
-			continue;
+		return 0;
 	}
 
 	/* Requested page is not present in compressed area */
@@ -233,15 +224,13 @@ static void zram_read(struct zram *zram, struct bio *bio)
 		pr_debug("Read before write: sector=%lu, size=%u",
 			 (ulong)(bio->bi_sector), bio->bi_size);
 		handle_zero_page(page);
-			index++;
-			continue;
+		return 0;
 	}
 
 	/* Page is stored uncompressed since it's incompressible */
 	if (unlikely(zram_test_flag(zram, index, ZRAM_UNCOMPRESSED))) {
 		handle_uncompressed_page(zram, page, index);
-			index++;
-			continue;
+		return 0;
 	}
 
 	user_mem = kmap_atomic(page, KM_USER0);
@@ -250,8 +239,7 @@ static void zram_read(struct zram *zram, struct bio *bio)
 	cmem = kmap_atomic(zram->table[index].page, KM_USER1) +
 		zram->table[index].offset;
 
-		ret = lzo1x_decompress_safe(
-			cmem + sizeof(*zheader),
+	ret = lzo1x_decompress_safe(cmem + sizeof(*zheader),
 				    xv_get_object_size(cmem) - sizeof(*zheader),
 				    user_mem, &clen);
 
@@ -260,34 +248,18 @@ static void zram_read(struct zram *zram, struct bio *bio)
 
 	/* Should NEVER happen. Return bio error if it does. */
 	if (unlikely(ret != LZO_E_OK)) {
-			pr_err("Decompression failed! err=%d, page=%u\n",
-				ret, index);
+		pr_err("Decompression failed! err=%d, page=%u\n", ret, index);
 		zram_stat64_inc(zram, &zram->stats.failed_reads);
-			goto out;
+		return ret;
 	}
 
 	flush_dcache_page(page);
-		index++;
-	}
-
-	set_bit(BIO_UPTODATE, &bio->bi_flags);
-	bio_endio(bio, 0);
-	return;
 
-out:
-	bio_io_error(bio);
+	return 0;
 }
 
-static void zram_write(struct zram *zram, struct bio *bio)
+static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index)
 {
-	int i;
-	u32 index;
-	struct bio_vec *bvec;
-
-	zram_stat64_inc(zram, &zram->stats.num_writes);
-	index = bio->bi_sector >> SECTORS_PER_PAGE_SHIFT;
-
-	bio_for_each_segment(bvec, bio, i) {
 	int ret;
 	u32 offset;
 	size_t clen;
@@ -314,8 +286,7 @@ static void zram_write(struct zram *zram, struct bio *bio)
 		mutex_unlock(&zram->lock);
 		zram_stat_inc(&zram->stats.pages_zero);
 		zram_set_flag(zram, index, ZRAM_ZERO);
-			index++;
-			continue;
+		return 0;
 	}
 
 	ret = lzo1x_1_compress(user_mem, PAGE_SIZE, src, &clen,
@@ -327,7 +298,7 @@ static void zram_write(struct zram *zram, struct bio *bio)
 		mutex_unlock(&zram->lock);
 		pr_err("Compression failed! err=%d\n", ret);
 		zram_stat64_inc(zram, &zram->stats.failed_writes);
-			goto out;
+		return ret;
 	}
 
 	/*
@@ -342,9 +313,8 @@ static void zram_write(struct zram *zram, struct bio *bio)
 			mutex_unlock(&zram->lock);
 			pr_info("Error allocating memory for "
 				"incompressible page: %u\n", index);
-				zram_stat64_inc(zram,
-					&zram->stats.failed_writes);
-				goto out;
+			zram_stat64_inc(zram, &zram->stats.failed_writes);
+				return -ENOMEM;
 			}
 
 		offset = 0;
@@ -362,7 +332,7 @@ static void zram_write(struct zram *zram, struct bio *bio)
 		pr_info("Error allocating memory for compressed "
 			"page: %u, size=%zu\n", index, clen);
 		zram_stat64_inc(zram, &zram->stats.failed_writes);
-			goto out;
+		return -ENOMEM;
 	}
 
 memstore:
@@ -393,6 +363,39 @@ static void zram_write(struct zram *zram, struct bio *bio)
 		zram_stat_inc(&zram->stats.good_compress);
 
 	mutex_unlock(&zram->lock);
+
+	return 0;
+}
+
+static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index,
+			struct bio *bio, int rw)
+{
+	if (rw == READ)
+		return zram_bvec_read(zram, bvec, index, bio);
+
+	return zram_bvec_write(zram, bvec, index);
+}
+
+static void __zram_make_request(struct zram *zram, struct bio *bio, int rw)
+{
+	int i;
+	u32 index;
+	struct bio_vec *bvec;
+
+	switch (rw) {
+	case READ:
+		zram_stat64_inc(zram, &zram->stats.num_reads);
+		break;
+	case WRITE:
+		zram_stat64_inc(zram, &zram->stats.num_writes);
+		break;
+	}
+
+	index = bio->bi_sector >> SECTORS_PER_PAGE_SHIFT;
+
+	bio_for_each_segment(bvec, bio, i) {
+		if (zram_bvec_rw(zram, bvec, index, bio, rw) < 0)
+			goto out;
 		index++;
 	}
 
@@ -439,15 +442,7 @@ static int zram_make_request(struct request_queue *queue, struct bio *bio)
 		return 0;
 	}
 
-	switch (bio_data_dir(bio)) {
-	case READ:
-		zram_read(zram, bio);
-		break;
-
-	case WRITE:
-		zram_write(zram, bio);
-		break;
-	}
+	__zram_make_request(zram, bio, bio_data_dir(bio));
 
 	return 0;
 }