[PATCH 1/6] jffs2: replace per-superblock verify buffer with per-write buffer

[zhouminqiang]

Subsequent patches will extend write verification to additional write
paths that may execute concurrently. A shared per-superblock buffer
would require a coarse lock to serialize all verification, hurting
concurrency.

To avoid this contention, remove the wbuf_verify field from
jffs2_sb_info, along with the scattered kmalloc/kfree of wbuf_verify
in jffs2_nand_flash_setup, jffs2_dataflash_setup,
jffs2_nor_wbuf_flash_setup and their corresponding cleanup functions.

Instead, allocate a temporary buffer inside jffs2_verify_write(),
giving each invocation its own buffer and eliminating the shared state.

Signed-off-by: zhouminqiang <zhouminqiang2 at huawei.com>
---
 fs/jffs2/jffs2_fs_sb.h |  3 ---
 fs/jffs2/wbuf.c        | 61 ++++++++++++++++--------------------------
 2 files changed, 23 insertions(+), 41 deletions(-)

diff --git a/fs/jffs2/jffs2_fs_sb.h b/fs/jffs2/jffs2_fs_sb.h
index 5a7091746f68..8a75870d3fc8 100644
--- a/fs/jffs2/jffs2_fs_sb.h
+++ b/fs/jffs2/jffs2_fs_sb.h
@@ -124,9 +124,6 @@ struct jffs2_sb_info {
 
 	uint32_t wbuf_pagesize; /* 0 for NOR and other flashes with no wbuf */
 
-#ifdef CONFIG_JFFS2_FS_WBUF_VERIFY
-	unsigned char *wbuf_verify; /* read-back buffer for verification */
-#endif
 #ifdef CONFIG_JFFS2_FS_WRITEBUFFER
 	unsigned char *wbuf; /* Write-behind buffer for NAND flash */
 	uint32_t wbuf_ofs;
diff --git a/fs/jffs2/wbuf.c b/fs/jffs2/wbuf.c
index 3b7803c75d58..7e4608b43a4e 100644
--- a/fs/jffs2/wbuf.c
+++ b/fs/jffs2/wbuf.c
@@ -15,6 +15,7 @@
 
 #include <linux/kernel.h>
 #include <linux/slab.h>
+#include <linux/vmalloc.h>
 #include <linux/mtd/mtd.h>
 #include <linux/crc32.h>
 #include <linux/mtd/rawnand.h>
@@ -233,19 +234,30 @@ static int jffs2_verify_write(struct jffs2_sb_info *c, unsigned char *buf,
 	int ret;
 	size_t retlen;
 	char *eccstr;
+	void *verify_buf;
 
-	ret = mtd_read(c->mtd, ofs, c->wbuf_pagesize, &retlen, c->wbuf_verify);
+	verify_buf = __vmalloc(c->wbuf_pagesize, GFP_NOFS);
+	if (!verify_buf) {
+		pr_warn("%s(): verify buffer allocation failed, skipping verification\n",
+			__func__);
+		return 0;
+	}
+
+	ret = mtd_read(c->mtd, ofs, c->wbuf_pagesize, &retlen, verify_buf);
 	if (ret && ret != -EUCLEAN && ret != -EBADMSG) {
 		pr_warn("%s(): Read back of page at %08x failed: %d\n",
 			__func__, c->wbuf_ofs, ret);
-		return ret;
+		goto out_free;
 	} else if (retlen != c->wbuf_pagesize) {
 		pr_warn("%s(): Read back of page at %08x gave short read: %zd not %d\n",
 			__func__, ofs, retlen, c->wbuf_pagesize);
-		return -EIO;
+		ret = -EIO;
+		goto out_free;
+	}
+	if (!memcmp(buf, verify_buf, c->wbuf_pagesize)) {
+		ret = 0;
+		goto out_free;
 	}
-	if (!memcmp(buf, c->wbuf_verify, c->wbuf_pagesize))
-		return 0;
 
 	if (ret == -EUCLEAN)
 		eccstr = "corrected";
@@ -261,9 +273,14 @@ static int jffs2_verify_write(struct jffs2_sb_info *c, unsigned char *buf,
 
 	pr_warn("Read back:\n");
 	print_hex_dump(KERN_WARNING, "", DUMP_PREFIX_OFFSET, 16, 1,
-		       c->wbuf_verify, c->wbuf_pagesize, 0);
+		       verify_buf, c->wbuf_pagesize, 0);
 
+	vfree(verify_buf);
 	return -EIO;
+
+out_free:
+	vfree(verify_buf);
+	return ret;
 }
 #else
 #define jffs2_verify_write(c,b,o) (0)
@@ -1214,22 +1231,11 @@ int jffs2_nand_flash_setup(struct jffs2_sb_info *c)
 		return -ENOMEM;
 	}
 
-#ifdef CONFIG_JFFS2_FS_WBUF_VERIFY
-	c->wbuf_verify = kmalloc(c->wbuf_pagesize, GFP_KERNEL);
-	if (!c->wbuf_verify) {
-		kfree(c->oobbuf);
-		kfree(c->wbuf);
-		return -ENOMEM;
-	}
-#endif
 	return 0;
 }
 
 void jffs2_nand_flash_cleanup(struct jffs2_sb_info *c)
 {
-#ifdef CONFIG_JFFS2_FS_WBUF_VERIFY
-	kfree(c->wbuf_verify);
-#endif
 	kfree(c->wbuf);
 	kfree(c->oobbuf);
 }
@@ -1269,14 +1275,6 @@ int jffs2_dataflash_setup(struct jffs2_sb_info *c) {
 	if (!c->wbuf)
 		return -ENOMEM;
 
-#ifdef CONFIG_JFFS2_FS_WBUF_VERIFY
-	c->wbuf_verify = kmalloc(c->wbuf_pagesize, GFP_KERNEL);
-	if (!c->wbuf_verify) {
-		kfree(c->wbuf);
-		return -ENOMEM;
-	}
-#endif
-
 	pr_info("write-buffering enabled buffer (%d) erasesize (%d)\n",
 		c->wbuf_pagesize, c->sector_size);
 
@@ -1284,9 +1282,6 @@ int jffs2_dataflash_setup(struct jffs2_sb_info *c) {
 }
 
 void jffs2_dataflash_cleanup(struct jffs2_sb_info *c) {
-#ifdef CONFIG_JFFS2_FS_WBUF_VERIFY
-	kfree(c->wbuf_verify);
-#endif
 	kfree(c->wbuf);
 }
 
@@ -1306,20 +1301,10 @@ int jffs2_nor_wbuf_flash_setup(struct jffs2_sb_info *c) {
 	if (!c->wbuf)
 		return -ENOMEM;
 
-#ifdef CONFIG_JFFS2_FS_WBUF_VERIFY
-	c->wbuf_verify = kmalloc(c->wbuf_pagesize, GFP_KERNEL);
-	if (!c->wbuf_verify) {
-		kfree(c->wbuf);
-		return -ENOMEM;
-	}
-#endif
 	return 0;
 }
 
 void jffs2_nor_wbuf_flash_cleanup(struct jffs2_sb_info *c) {
-#ifdef CONFIG_JFFS2_FS_WBUF_VERIFY
-	kfree(c->wbuf_verify);
-#endif
 	kfree(c->wbuf);
 }
 
-- 
2.52.0