linux-kernel - [PATCH] Propagate CRAMFS uncompression errors, v2.1

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Date:	Wed, 11 Feb 2009 14:46:14 -0800
From:	VomLehn <dvomlehn@...co.com>
To:	akpm@...ux-foundation.org
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] Propagate CRAMFS uncompression errors, v2.1

Decompression errors can arise due to corruption of compressed blocks
on flash or in memory. This patch propagates errors detected during
decompression back to the block layer.

Version v2.1:
Now checkpatch clean.

Version v2:
This version revised based on suggestions from Andrew Morton.

Signed-off-by: David VomLehn <dvomlehn@...co.com>
---
 fs/cramfs/inode.c      |   36 ++++++++++++++++++++++++++----------
 fs/cramfs/uncompress.c |    2 +-
 2 files changed, 27 insertions(+), 11 deletions(-)

diff --git a/fs/cramfs/inode.c b/fs/cramfs/inode.c
index f40423e..95f42dd 100644
--- a/fs/cramfs/inode.c
+++ b/fs/cramfs/inode.c
@@ -461,11 +461,14 @@ static struct dentry * cramfs_lookup(struct inode *dir, struct dentry *dentry, s
 static int cramfs_readpage(struct file *file, struct page * page)
 {
 	struct inode *inode = page->mapping->host;
-	u32 maxblock, bytes_filled;
+	u32 maxblock;
+	int bytes_filled;
 	void *pgdata;
 
 	maxblock = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 	bytes_filled = 0;
+	pgdata = kmap(page);
+
 	if (page->index < maxblock) {
 		struct super_block *sb = inode->i_sb;
 		u32 blkptr_offset = OFFSET(inode) + page->index*4;
@@ -474,30 +477,43 @@ static int cramfs_readpage(struct file *file, struct page * page)
 		start_offset = OFFSET(inode) + maxblock*4;
 		mutex_lock(&read_mutex);
 		if (page->index)
-			start_offset = *(u32 *) cramfs_read(sb, blkptr_offset-4, 4);
-		compr_len = (*(u32 *) cramfs_read(sb, blkptr_offset, 4) - start_offset);
+			start_offset = *(u32 *) cramfs_read(sb, blkptr_offset-4,
+				4);
+		compr_len = (*(u32 *) cramfs_read(sb, blkptr_offset, 4) -
+			start_offset);
 		mutex_unlock(&read_mutex);
-		pgdata = kmap(page);
+
 		if (compr_len == 0)
 			; /* hole */
-		else if (compr_len > (PAGE_CACHE_SIZE << 1))
-			printk(KERN_ERR "cramfs: bad compressed blocksize %u\n", compr_len);
-		else {
+		else if (unlikely(compr_len > (PAGE_CACHE_SIZE << 1))) {
+			pr_err("cramfs: bad compressed blocksize %u\n",
+				compr_len);
+			goto err;
+		} else {
 			mutex_lock(&read_mutex);
 			bytes_filled = cramfs_uncompress_block(pgdata,
 				 PAGE_CACHE_SIZE,
 				 cramfs_read(sb, start_offset, compr_len),
 				 compr_len);
 			mutex_unlock(&read_mutex);
+			if (unlikely(bytes_filled < 0))
+				goto err;
 		}
-	} else
-		pgdata = kmap(page);
+	}
+
 	memset(pgdata + bytes_filled, 0, PAGE_CACHE_SIZE - bytes_filled);
-	kunmap(page);
 	flush_dcache_page(page);
+	kunmap(page);
 	SetPageUptodate(page);
 	unlock_page(page);
 	return 0;
+
+err:
+	kunmap(page);
+	ClearPageUptodate(page);
+	SetPageError(page);
+	unlock_page(page);
+	return 0;
 }
 
 static const struct address_space_operations cramfs_aops = {
diff --git a/fs/cramfs/uncompress.c b/fs/cramfs/uncompress.c
index fc3ccb7..0233298 100644
--- a/fs/cramfs/uncompress.c
+++ b/fs/cramfs/uncompress.c
@@ -50,7 +50,7 @@ int cramfs_uncompress_block(void *dst, int dstlen, void *src, int srclen)
 err:
 	printk("Error %d while decompressing!\n", err);
 	printk("%p(%d)->%p(%d)\n", src, srclen, dst, dstlen);
-	return 0;
+	return -EIO;
 }
 
 int cramfs_uncompress_init(void)
--
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