> I discovered one minor bug in BTRFS filesystem. You sure did. > ERROR: ioctl(BTRFS_IOC_GET_DEV_STATS) on /dev/sde failed: No such device > > But this is not true ... all specified devices exist and are members > of btrfs filesystem. In dmesg I see this: > ... > [973077.099118] btrfs: get dev_stats failed, not yet valid > .... > > What makes device statistics valid ? I tried doing full filesystem > scrub ... but it did not fix that issue. The stats are only initialized (considered valid) for devices that are known at mount. You could unmount and mount after adding (or replacing) new devices and they'd start returning stats. The following (bad) patch illustrates the problem, but the code should be restructured so stats are reliably read as devices are added. - z From: Zach Brown <zab@xxxxxxxxxx> Date: Mon, 30 Sep 2013 17:48:05 -0400 Subject: [PATCH] btrfs: init device stats for new devices Device stats are only initialized (read from tree items) on mount. Trying to read device stats after adding or replacing new devices will return errors. This cheesy patch demonstrates the problem, but this should really be a natural side-effect of adding devices to the fs_devices list. We have evidence that trying to do it by hand doesn't work. Any preferences for how to restructure this? --- fs/btrfs/dev-replace.c | 4 +++- fs/btrfs/volumes.c | 6 ++++++ 2 files changed, 9 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c index 5d84443..7309096 100644 --- a/fs/btrfs/dev-replace.c +++ b/fs/btrfs/dev-replace.c @@ -556,7 +556,9 @@ static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info, mutex_unlock(&dev_replace->lock_finishing_cancel_unmount); - return 0; + ret = btrfs_init_dev_stats(root->fs_info); + + return ret; } static void btrfs_dev_replace_update_device_in_mapping_tree( diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 0431147..e4ccc9b 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -2126,6 +2126,9 @@ int btrfs_init_new_device(struct btrfs_root *root, char *device_path) ret = btrfs_commit_transaction(trans, root); } + if (!ret) + ret = btrfs_init_dev_stats(root->fs_info); + return ret; error_trans: @@ -6060,6 +6063,9 @@ int btrfs_init_dev_stats(struct btrfs_fs_info *fs_info) int item_size; struct btrfs_dev_stats_item *ptr; + if (device->dev_stats_valid) + continue; + key.objectid = 0; key.type = BTRFS_DEV_STATS_KEY; key.offset = device->devid; -- 1.7.11.7 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
