On Tue, Apr 12, 2016 at 10:15:51PM +0800, Anand Jain wrote:
> From: Qu Wenruo <quwenruo@xxxxxxxxxxxxxx>
>
> 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 <quwenruo@xxxxxxxxxxxxxx>
> ---
> fs/btrfs/volumes.c | 63 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
> fs/btrfs/volumes.h | 1 +
> 2 files changed, 64 insertions(+)
>
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index 9d72dabdddfc..a351c5dd9e9b 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -7039,3 +7039,66 @@ 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));
> + /* 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), writebale mount is not allowed",
> + missing, max_tolerated);
Typo: s/writebale/writeable/
--
Yauhen Kharuzhy
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