Merge branch 'for-linus-4.10' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs

Pull btrfs fixes from Chris Mason:
 "This has two last minute fixes. The highest priority here is a
  regression fix for the decompression code, but we also fixed up a
  problem with the 32-bit compat ioctls.

  The decompression bug could hand back the wrong data on big reads when
  zlib was used. I have a larger cleanup to make the math here less
  error prone, but at this stage in the release Omar's patch is the best
  choice"

* 'for-linus-4.10' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs:
  btrfs: fix btrfs_decompress_buf2page()
  btrfs: fix btrfs_compat_ioctl failures on non-compat ioctls

fs/btrfs/compression.c

@@ -1024,6 +1024,7 @@ int btrfs_decompress_buf2page(char *buf, unsigned long buf_start,
 	unsigned long buf_offset;
 	unsigned long current_buf_start;
 	unsigned long start_byte;
+	unsigned long prev_start_byte;
 	unsigned long working_bytes = total_out - buf_start;
 	unsigned long bytes;
 	char *kaddr;
@@ -1071,9 +1072,16 @@ int btrfs_decompress_buf2page(char *buf, unsigned long buf_start,
 		if (!bio->bi_iter.bi_size)
 			return 0;
 		bvec = bio_iter_iovec(bio, bio->bi_iter);
-
+		prev_start_byte = start_byte;
 		start_byte = page_offset(bvec.bv_page) - disk_start;
 
+		/*
+		 * We need to make sure we're only adjusting
+		 * our offset into compression working buffer when
+		 * we're switching pages.  Otherwise we can incorrectly
+		 * keep copying when we were actually done.
+		 */
+		if (start_byte != prev_start_byte) {
 			/*
 			 * make sure our new page is covered by this
 			 * working buffer
@@ -1093,6 +1101,7 @@ int btrfs_decompress_buf2page(char *buf, unsigned long buf_start,
 				current_buf_start = buf_start + buf_offset;
 			}
 		}
+	}
 
 	return 1;
 }

fs/btrfs/ioctl.c

@@ -5653,6 +5653,10 @@ long btrfs_ioctl(struct file *file, unsigned int
 #ifdef CONFIG_COMPAT
 long btrfs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 {
+	/*
+	 * These all access 32-bit values anyway so no further
+	 * handling is necessary.
+	 */
 	switch (cmd) {
 	case FS_IOC32_GETFLAGS:
 		cmd = FS_IOC_GETFLAGS;
@@ -5663,8 +5667,6 @@ long btrfs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 	case FS_IOC32_GETVERSION:
 		cmd = FS_IOC_GETVERSION;
 		break;
-	default:
-		return -ENOIOCTLCMD;
 	}
 
 	return btrfs_ioctl(file, cmd, (unsigned long) compat_ptr(arg));