linux-kernel - [PATCH 1/2] zram: Less checks in zram_bvec

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Date:	Fri, 11 Dec 2015 19:24:26 +0100
From:	SF Markus Elfring <elfring@...rs.sourceforge.net>
To:	LKML <linux-kernel@...r.kernel.org>,
	Minchan Kim <minchan@...nel.org>,
	Nitin Gupta <ngupta@...are.org>,
	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Cc:	kernel-janitors@...r.kernel.org,
	Julia Lawall <julia.lawall@...6.fr>
Subject: [PATCH 1/2] zram: Less checks in zram_bvec_write() after error
 detection

From: Markus Elfring <elfring@...rs.sourceforge.net>
Date: Fri, 11 Dec 2015 18:20:59 +0100

This issue was detected by using the Coccinelle software.

A few checks could be repeated by the zram_bvec_write() function
at two places even if the passed variables contained a null pointer.

* This implementation detail could be improved by adjustments
  for jump targets according to the Linux coding style convention.

* Let us return directly if a memory allocation failed.

* Drop unnecessary initialisations for the variables "uncmem"
  and "zstrm" then.

Signed-off-by: Markus Elfring <elfring@...rs.sourceforge.net>
---
 drivers/block/zram/zram_drv.c | 26 +++++++++++++-------------
 1 file changed, 13 insertions(+), 13 deletions(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 47915d7..69d7fcd 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -652,9 +652,9 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
 	size_t clen;
 	unsigned long handle;
 	struct page *page;
-	unsigned char *user_mem, *cmem, *src, *uncmem = NULL;
+	unsigned char *user_mem, *cmem, *src, *uncmem;
 	struct zram_meta *meta = zram->meta;
-	struct zcomp_strm *zstrm = NULL;
+	struct zcomp_strm *zstrm;
 	unsigned long alloced_pages;
 
 	page = bvec->bv_page;
@@ -664,13 +664,11 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
 		 * before to write the changes.
 		 */
 		uncmem = kmalloc(PAGE_SIZE, GFP_NOIO);
-		if (!uncmem) {
-			ret = -ENOMEM;
-			goto out;
-		}
+		if (!uncmem)
+			return -ENOMEM;
 		ret = zram_decompress_page(zram, uncmem, index);
 		if (ret)
-			goto out;
+			goto free_uncmem;
 	}
 
 	zstrm = zcomp_strm_find(zram->comp);
@@ -696,7 +694,7 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
 
 		atomic64_inc(&zram->stats.zero_pages);
 		ret = 0;
-		goto out;
+		goto check_strm;
 	}
 
 	ret = zcomp_compress(zram->comp, zstrm, uncmem, &clen);
@@ -708,7 +706,7 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
 
 	if (unlikely(ret)) {
 		pr_err("Compression failed! err=%d\n", ret);
-		goto out;
+		goto check_strm;
 	}
 	src = zstrm->buffer;
 	if (unlikely(clen > max_zpage_size)) {
@@ -722,7 +720,7 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
 		pr_err("Error allocating memory for compressed page: %u, size=%zu\n",
 			index, clen);
 		ret = -ENOMEM;
-		goto out;
+		goto check_strm;
 	}
 
 	alloced_pages = zs_get_total_pages(meta->mem_pool);
@@ -731,7 +729,7 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
 	if (zram->limit_pages && alloced_pages > zram->limit_pages) {
 		zs_free(meta->mem_pool, handle);
 		ret = -ENOMEM;
-		goto out;
+		goto check_strm;
 	}
 
 	cmem = zs_map_object(meta->mem_pool, handle, ZS_MM_WO);
@@ -762,11 +760,13 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
 	/* Update stats */
 	atomic64_add(clen, &zram->stats.compr_data_size);
 	atomic64_inc(&zram->stats.pages_stored);
-out:
+check_strm:
 	if (zstrm)
 		zcomp_strm_release(zram->comp, zstrm);
-	if (is_partial_io(bvec))
+	if (is_partial_io(bvec)) {
+free_uncmem:
 		kfree(uncmem);
+	}
 	return ret;
 }
 
-- 
2.6.3

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