On 28.06.2017 08:43, Qu Wenruo wrote:
> Introduce a new function, btrfs_check_rw_degradable(), to check if all
> chunks in btrfs is OK for degraded rw 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 <quwenruo@xxxxxxxxxxxxxx>
> Signed-off-by: Anand Jain <anand.jain@xxxxxxxxxx>
> ---
> fs/btrfs/volumes.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
> fs/btrfs/volumes.h | 1 +
> 2 files changed, 59 insertions(+)
>
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index c95f018d4a1e..7a72fbdb8262 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -6817,6 +6817,64 @@ int btrfs_read_sys_array(struct btrfs_fs_info *fs_info)
> return -EIO;
> }
>
> +/*
> + * Check if all chunks in the fs is OK for read-write degraded mount
> + *
> + * Return true if all chunks meet the minimal RW mount requirement.
> + * Return false if any chunk doesn't meet the minimal RW mount requirement.
> + */
> +bool btrfs_check_rw_degradable(struct btrfs_fs_info *fs_info)
> +{
> + struct btrfs_mapping_tree *map_tree = &fs_info->mapping_tree;
> + struct extent_map *em;
> + u64 next_start = 0;
> + bool ret = true;
> +
> + 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 chunk at all? Return false anyway */
> + if (!em) {
> + ret = false;
> + goto out;
> + }
> + while (em) {
> + struct map_lookup *map;
> + int missing = 0;
> + int max_tolerated;
> + int i;
> +
> + map = em->map_lookup;
> + max_tolerated =
> + btrfs_get_num_tolerated_disk_barrier_failures(
> + map->type);
> + for (i = 0; i < map->num_stripes; i++) {
> + struct btrfs_device *dev = map->stripes[i].dev;
> +
> + if (!dev || !dev->bdev || dev->missing ||
> + dev->last_flush_error)
> + missing++;
> + }
> + if (missing > max_tolerated) {
> + ret = false;
> + btrfs_warn(fs_info,
> + "chunk %llu missing %d devices, max tolerance is %d for writeble mount",
> + em->start, missing, max_tolerated);
> + free_extent_map(em);
> + goto out;
> + }
> + next_start = extent_map_end(em);
> + 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:
> + return ret;
> +}
> +
Nit but I think in this function it would be best to directly return
true/false based on context rather than having the superfluous goto.
> int btrfs_read_chunk_tree(struct btrfs_fs_info *fs_info)
> {
> struct btrfs_root *root = fs_info->chunk_root;
> diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
> index 6f45fd60d15a..a5897c7a7e86 100644
> --- a/fs/btrfs/volumes.h
> +++ b/fs/btrfs/volumes.h
> @@ -543,4 +543,5 @@ 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);
>
> +bool btrfs_check_rw_degradable(struct btrfs_fs_info *fs_info);
> #endif
>
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