iomap: swapfile tweaks

From: Omar Sandoval <[email protected]>

Currently, for an invalid swap file, we print the same error message regardless of the reason. This isn't very useful for an admin, who will likely want to know why exactly they can't use their swap file. So, let's add specific error messages for each reason, and also move the bdev check after the flags checks, since the latter are more fundamental.

Reviewed-by Darrick J. Wong <[email protected]>

Signed-off-by Omar Sandoval <[email protected]>

---
 fs/iomap.c | 40 ++++++++++++++++++++++++----------------
 1 file changed, 24 insertions(+), 16 deletions(-)

fs/iomap.c +24 -16

index d193390a1c20..89517442e296 100644
@@ -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;
 }
 
 /*

Signature · 1 line

2.17.0

From: Omar Sandoval <[email protected]>

generic_swapfile_activate() doesn't allow holes, so we should be consistent here. This is also a bit safer: if the user creates a swapfile with, say, truncate -s $SIZE followed by mkswap, they should really get an error and not much less swap space than they expected. swapon(8) will error out before calling swapon(2) if the file has holes, anyways.

Fixes 9d93388b0afe ("iomap: add a swapfile activation function")

Reviewed-by Darrick J. Wong <[email protected]>

Signed-off-by Omar Sandoval <[email protected]>

---
 fs/iomap.c | 5 -----
 1 file changed, 5 deletions(-)

fs/iomap.c +0 -5

index 89517442e296..f2456d0d8ddd 100644
@@ -1220,10 +1220,6 @@ static loff_t iomap_swapfile_activate_actor(struct inode *inode, loff_t pos,
 		return -EINVAL;
 	}
 
-	/* Skip holes. */
-	if (iomap->type == IOMAP_HOLE)
-		goto out;
-
 	/* Only real or unwritten extents. */
 	if (iomap->type != IOMAP_MAPPED && iomap->type != IOMAP_UNWRITTEN) {
 		pr_err("swapon: file has unallocated extents\n");

@@ -1259,7 +1255,6 @@ static loff_t iomap_swapfile_activate_actor(struct inode *inode, loff_t pos,
 			return error;
 		memcpy(&isi->iomap, iomap, sizeof(isi->iomap));
 	}
-out:
 	return count;
 }
 

Signature · 1 line

2.17.0

From: Omar Sandoval <[email protected]>

Changes from v2:

- Move up inline flag check, which Christoph is going to turn into a type at some point
- Remove null address check, since it doesn't make sense for IOMAP_MAPPED or IOMAP_UNWRITTEN

Omar Sandoval (2):
iomap: provide more useful errors for invalid swap files
iomap: don't allow holes in swapfiles

 fs/iomap.c | 43 +++++++++++++++++++++++--------------------

 1 file changed, 23 insertions(+), 20 deletions(-)

Signature · 6 lines

2.17.0

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