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/803815 Signed-off-by: Andy Whitcroft <[email protected]> --- fs/btrfs/super.c | 5 ++++- 1 files changed, 4 insertions(+), 1 deletions(-) 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); -- 1.7.4.1 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
