From: Qu Wenruo <quwen...@cn.fujitsu.com> Introduce a new function, btrfs_check_degradable(), to judge if all chunks in btrfs is OK for degraded mount.
It provides the new basis for accurate btrfs mount/remount and even runtime degraded mount check other than old one-size-fit-all method. Signed-off-by: Qu Wenruo <quwen...@cn.fujitsu.com> --- fs/btrfs/volumes.c | 67 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ fs/btrfs/volumes.h | 1 + 2 files changed, 68 insertions(+) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 4ff716d9b16c..f5fa5f88263c 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -7065,3 +7065,70 @@ static void btrfs_close_one_device(struct btrfs_device *device) call_rcu(&device->rcu, free_device); } + +/* + * Check if all chunks in the fs is OK for degraded mount + * Caller itself should do extra check if DEGRADED mount option is given + * for >0 return value. + * + * Return 0 if all chunks are OK. + * Return >0 if all chunks are degradable but not all OK. + * Return <0 if any chunk is not degradable or other bug. + */ +int btrfs_check_degradable(struct btrfs_fs_info *fs_info, unsigned flags) +{ + struct btrfs_mapping_tree *map_tree = &fs_info->mapping_tree; + struct extent_map *em; + u64 next_start = 0; + int ret = 0; + + if (flags & MS_RDONLY) + return 0; + + read_lock(&map_tree->map_tree.lock); + em = lookup_extent_mapping(&map_tree->map_tree, 0, (u64)(-1)); + read_unlock(&map_tree->map_tree.lock); + /* No any chunk? Should be a huge bug */ + if (!em) { + ret = -ENOENT; + goto out; + } + + while (em) { + struct map_lookup *map; + int missing = 0; + int max_tolerated; + int i; + + map = (struct map_lookup *) em->bdev; + max_tolerated = + btrfs_get_num_tolerated_disk_barrier_failures( + map->type); + for (i = 0; i < map->num_stripes; i++) { + if (map->stripes[i].dev->missing) + missing++; + } + if (missing > max_tolerated) { + ret = -EIO; + btrfs_warn(fs_info, + "missing devices(%d) exceeds the limit(%d), writeable mount is not allowed", + missing, max_tolerated); + goto out; + } else if (missing) + ret = 1; + next_start = extent_map_end(em); + + /* + * Alwasy search range [next_start, (u64)-1) to find the next + * chunk map + */ + free_extent_map(em); + read_lock(&map_tree->map_tree.lock); + em = lookup_extent_mapping(&map_tree->map_tree, next_start, + (u64)(-1) - next_start); + read_unlock(&map_tree->map_tree.lock); + } +out: + free_extent_map(em); + return ret; +} diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h index 93e0a2560366..ae9d552c93bf 100644 --- a/fs/btrfs/volumes.h +++ b/fs/btrfs/volumes.h @@ -568,5 +568,6 @@ static inline void unlock_chunks(struct btrfs_root *root) struct list_head *btrfs_get_fs_uuids(void); void btrfs_set_fs_info_ptr(struct btrfs_fs_info *fs_info); void btrfs_reset_fs_info_ptr(struct btrfs_fs_info *fs_info); +int btrfs_check_degradable(struct btrfs_fs_info *fs_info, unsigned flags); #endif -- 2.7.0 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html