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>

diff --git a/btrfs-image.c b/btrfs-image.c
index 3684a05..b225325 100644 (file)
--- a/btrfs-image.c
+++ b/btrfs-image.c
@@ -894,7 +894,7 @@ static int read_data_extent(struct metadump_struct *md,
 
                device = multi->stripes[0].dev;
 
-               if (device->fd == 0) {
+               if (device->fd <= 0) {
                        fprintf(stderr,
                                "Device we need to read from is not open\n");
                        free(multi);

diff --git a/disk-io.c b/disk-io.c
index 46a5a46..1d48893 100644 (file)
--- 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;

diff --git a/extent_io.c b/extent_io.c
index 5d49710..07695ef 100644 (file)
--- a/extent_io.c
+++ b/extent_io.c
@@ -714,7 +714,7 @@ int read_data_from_disk(struct btrfs_fs_info *info, void *buf, u64 offset,
                device = multi->stripes[0].dev;
 
                read_len = min(bytes_left, read_len);
-               if (device->fd == 0) {
+               if (device->fd <= 0) {
                        kfree(multi);
                        return -EIO;
                }
@@ -790,7 +790,7 @@ int write_data_to_disk(struct btrfs_fs_info *info, void *buf, u64 offset,
                        raid_map = NULL;
                } else while (dev_nr < multi->num_stripes) {
                        device = multi->stripes[dev_nr].dev;
-                       if (device->fd == 0) {
+                       if (device->fd <= 0) {
                                kfree(multi);
                                return -EIO;
                        }