| Message ID | 1311764491-5687-1-git-send-email-apw@canonical.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 07/27/2011 07:01 AM, Andy Whitcroft wrote: > When we mount a btrfs filesystem from read-only media there will be no > read/write devices; for example mounting an SD card with its lock enabled. > This triggers an immediate BUG during mount: > > kernel BUG at .../fs/btrfs/super.c:984! > > This is triggered by statfs when calculating the free space in the > filesytem. We bug if the number of read/write devices is 0. > > It seems more appropriate to indicate we have no writable space. Note > that this does make df return 0 free blocks on a read-only device. > Whether that is reasonable is debatable. No it's not, it's wrong. We should just look at the devices in general and not just the rw_devices. We can still get the right info out, if you mount a ext* fs ro you still get the right output from df. Thanks, Josef -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c index 15634d4..8d3f9b0 100644 --- a/fs/btrfs/super.c +++ b/fs/btrfs/super.c @@ -981,7 +981,10 @@ static int btrfs_calc_avail_data_space(struct btrfs_root *root, u64 *free_bytes) int ret; nr_devices = fs_info->fs_devices->rw_devices; - BUG_ON(!nr_devices); + if (!nr_devices) { + *free_bytes = 0; + return 0; + } devices_info = kmalloc(sizeof(*devices_info) * nr_devices, GFP_NOFS);
When we mount a btrfs filesystem from read-only media there will be no read/write devices; for example mounting an SD card with its lock enabled. This triggers an immediate BUG during mount: kernel BUG at .../fs/btrfs/super.c:984! This is triggered by statfs when calculating the free space in the filesytem. We bug if the number of read/write devices is 0. It seems more appropriate to indicate we have no writable space. Note that this does make df return 0 free blocks on a read-only device. Whether that is reasonable is debatable. BugLink: http://bugs.launchpad.net/bugs/816770 Signed-off-by: Andy Whitcroft <apw@canonical.com> --- fs/btrfs/super.c | 5 ++++- 1 files changed, 4 insertions(+), 1 deletions(-)