btrfs-progs: Avoid reading bad fd in case of missing device.

Offline btrfs tools, like btrfs-image, will infinitely loop when there
is missing device.

The reason is, for missing device, it's fd will be set to -1, but before
we reading, we only check the fd validation by checking if it's 0.
So in that case, -1 will pass the validation check, and cause pread to
return 0, and loop to read.

Just change the validation check from "== 0" to "<= 0" to avoid such
problem.

Reported-by: Timothy Normand Miller <theosib@gmail.com>
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/disk-io.c b/disk-io.c
index 46a5a46d..1d488932 100644
--- a/disk-io.c
+++ b/disk-io.c
@@ -266,7 +266,7 @@ int read_whole_eb(struct btrfs_fs_info *info, struct extent_buffer *eb, int mirr
 			}
 			device = multi->stripes[0].dev;
 
-			if (device->fd == 0) {
+			if (device->fd <= 0) {
 				kfree(multi);
 				return -EIO;
 			}
@@ -385,7 +385,7 @@ int read_extent_data(struct btrfs_root *root, char *data,
 	}
 	device = multi->stripes[0].dev;
 
-	if (device->fd == 0)
+	if (device->fd <= 0)
 		goto err;
 	if (*len > max_len)
 		*len = max_len;