Re: [PATCH v2 1/2] iomap: provide more useful errors for invalid swap files

[Omar Sandoval <osandov@osandov.com>]

On Wed, May 16, 2018 at 10:25:31AM -0700, Christoph Hellwig wrote:
> On Wed, May 16, 2018 at 09:45:50AM -0700, Omar Sandoval wrote:
> > +	if ((iomap->type != IOMAP_MAPPED && iomap->type != IOMAP_UNWRITTEN) ||
> > +	    iomap->addr == IOMAP_NULL_ADDR) {
> > +		pr_err("swapon: file has unallocated extents\n");
> > +		return -EINVAL;
> > +	}
> 
> The two are really different cases - IOMAP_NULL_ADDR shouldn't really
> happen for any of the above.  Although we might have to move the
> inline check before the type check above for the message to make sense.
> 
> I have a patch in the local queue that makes inline a type instead of
> a flag, btw as it really isn't a flag.

So something like this, moving the inline check and removing the hole
check since that doesn't make sense for mapped or unwritten? Then the
inline flag check can be converted to a type check.

diff --git a/fs/iomap.c b/fs/iomap.c
index d193390a1c20..89517442e296 100644
--- a/fs/iomap.c
+++ b/fs/iomap.c
@@ -1214,26 +1214,37 @@ static loff_t iomap_swapfile_activate_actor(struct inode *inode, loff_t pos,
 	struct iomap_swapfile_info *isi = data;
 	int error;
 
+	/* No inline data. */
+	if (iomap->flags & IOMAP_F_DATA_INLINE) {
+		pr_err("swapon: file is inline\n");
+		return -EINVAL;
+	}
+
 	/* Skip holes. */
 	if (iomap->type == IOMAP_HOLE)
 		goto out;
 
-	/* Only one bdev per swap file. */
-	if (iomap->bdev != isi->sis->bdev)
-		goto err;
-
 	/* Only real or unwritten extents. */
-	if (iomap->type != IOMAP_MAPPED && iomap->type != IOMAP_UNWRITTEN)
-		goto err;
+	if (iomap->type != IOMAP_MAPPED && iomap->type != IOMAP_UNWRITTEN) {
+		pr_err("swapon: file has unallocated extents\n");
+		return -EINVAL;
+	}
 
-	/* No uncommitted metadata or shared blocks or inline data. */
-	if (iomap->flags & (IOMAP_F_DIRTY | IOMAP_F_SHARED |
-			    IOMAP_F_DATA_INLINE))
-		goto err;
+	/* No uncommitted metadata or shared blocks. */
+	if (iomap->flags & IOMAP_F_DIRTY) {
+		pr_err("swapon: file is not committed\n");
+		return -EINVAL;
+	}
+	if (iomap->flags & IOMAP_F_SHARED) {
+		pr_err("swapon: file has shared extents\n");
+		return -EINVAL;
+	}
 
-	/* No null physical addresses. */
-	if (iomap->addr == IOMAP_NULL_ADDR)
-		goto err;
+	/* Only one bdev per swap file. */
+	if (iomap->bdev != isi->sis->bdev) {
+		pr_err("swapon: file is on multiple devices\n");
+		return -EINVAL;
+	}
 
 	if (isi->iomap.length == 0) {
 		/* No accumulated extent, so just store it. */
@@ -1250,9 +1261,6 @@ static loff_t iomap_swapfile_activate_actor(struct inode *inode, loff_t pos,
 	}
 out:
 	return count;
-err:
-	pr_err("swapon: file cannot be used for swap\n");
-	return -EINVAL;
 }
 
 /*