Clean up error reporting in block.c, so that it gives honest error strings

for the sorts of errors we run into[1].  This also gives us room to put in a
vaguely appropriate casts to silence warnings since our compiler doesn't like
when we compare ssize_t to size_t[2].  Add a cast in sblock.c[3] to silence
a warning because of signed vs. size_t hell (again).  Clean up nearby
excessive parenthemutilation[4].

Reviewed by:	bde [2] [3]
Suggested by:	bde, many [1]
Submitted by:	bde [4]

An aside about [4], bde notes that we do not check for a negative value for
the fs bsize.  I'm nto going to do that in every situation we use it, one must
expect a reasonable program to pass down reasonable values.  Some foot shooting
protection I will tolerate, some I will not.  Also he suggests some possible
conditional improvements there, which I may take to heart.

PS: For me at least, this is now WARNS=5 clean...

2 files changed, 22 insertions, 13 deletions

diff --git a/lib/libufs/block.c b/lib/libufs/block.c
index efc39ef..5c019d4 100644
--- a/lib/libufs/block.c
+++ b/lib/libufs/block.c
@@ -59,16 +59,21 @@ bread(struct uufsd *disk, ufs2_daddr_t blockno, void *data, size_t size)
 	buf = data;
 
 	cnt = pread(disk->d_fd, data, size, (off_t)(blockno * disk->d_bsize));
-	/*
-	 * In case of failure, zero data, which must be fs_bsize.
-	 */
-	if (cnt != size) {
-		ERROR(disk, "short read from block device");
-		for (cnt = 0; cnt < MIN(size, disk->d_fs.fs_bsize); cnt++)
-			buf[cnt] = 0;
-		return -1;
+	if (cnt == -1) {
+		ERROR(disk, "read error from block device");
+		goto fail;
+	}
+	if (cnt == 0) {
+		ERROR(disk, "end of file from block device");
+		goto fail;
+	}
+	if ((size_t)cnt != size) {
+		ERROR(disk, "short read or read error from block device");
+		goto fail;
 	}
 	return cnt;
+fail:	memset(buf, 0, size);
+	return -1;
 }
 
 ssize_t
@@ -86,7 +91,11 @@ bwrite(struct uufsd *disk, ufs2_daddr_t blockno, const void *data, size_t size)
 	}
 
 	cnt = pwrite(disk->d_fd, data, size, (off_t)(blockno * disk->d_bsize));
-	if (cnt != size) {
+	if (cnt == -1) {
+		ERROR(disk, "read write to block device");
+		return -1;
+	}
+	if ((size_t)cnt != size) {
 		ERROR(disk, "short write to block device");
 		return -1;
 	}
diff --git a/lib/libufs/sblock.c b/lib/libufs/sblock.c
index 455fee0..7f87f65 100644
--- a/lib/libufs/sblock.c
+++ b/lib/libufs/sblock.c
@@ -64,11 +64,11 @@ sbread(struct uufsd *disk)
 		}
 		if (fs->fs_magic == FS_UFS1_MAGIC)
 			disk->d_ufs = 1;
-		if ((fs->fs_magic == FS_UFS2_MAGIC) &&
-		    (fs->fs_sblockloc == superblock))
+		if (fs->fs_magic == FS_UFS2_MAGIC &&
+		    fs->fs_sblockloc == superblock)
 			disk->d_ufs = 2;
-		if ((fs->fs_bsize <= MAXBSIZE) &&
-		    (fs->fs_bsize >= sizeof(*fs))) {
+		if (fs->fs_bsize <= MAXBSIZE &&
+		    (size_t)fs->fs_bsize >= sizeof(*fs)) {
 			if (disk->d_ufs)
 				break;
 		}