On Thu, Jul 03, 2014 at 06:22:13PM +0800, Miao Xie wrote:
> If we mounted a seed filesystem with degraded option, and then added a new
> device into the seed filesystem, then we found adding device failed because
> of the IO failure.
>
> Steps to reproduce:
> # mkfs.btrfs -d raid1 -m raid1 <dev0> <dev1>
> # btrfstune -S 1 <dev0>
> # mount <dev0> -o degraded <mnt>
> # btrfs device add -f <dev2> <mnt>
>
> It is because the original didn't set the chunk on the seed device to be
> read-only if the degraded flag was set. It was introduced by patch f48b90756,
> which fixed the problem the raid1 filesystem became read-only after one device
> of it was missing. But this fix method was not right, we should set the read-only
> flag according to the number of the missing devices, not the degraded mount
> option, if the number of the missing devices is less than the max error number
> that the profile of the chunk tolerates, we don't set it to be read-only.
Reviewed-by: Liu Bo <bo.li.liu@xxxxxxxxxx>
-liubo
>
> Cc: Josef Bacik <jbacik@xxxxxx>
> Signed-off-by: Miao Xie <miaox@xxxxxxxxxxxxxx>
> ---
> fs/btrfs/volumes.c | 52 ++++++++++++++++++++++++++++++++++++----------------
> 1 file changed, 36 insertions(+), 16 deletions(-)
>
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index 73a82e5..daecfa5 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -4584,12 +4584,31 @@ out:
> return ret;
> }
>
> +static inline int btrfs_chunk_max_errors(struct map_lookup *map)
> +{
> + int max_errors;
> +
> + if (map->type & (BTRFS_BLOCK_GROUP_RAID1 |
> + BTRFS_BLOCK_GROUP_RAID10 |
> + BTRFS_BLOCK_GROUP_RAID5 |
> + BTRFS_BLOCK_GROUP_DUP)) {
> + max_errors = 1;
> + } else if (map->type & BTRFS_BLOCK_GROUP_RAID6) {
> + max_errors = 2;
> + } else {
> + max_errors = 0;
> + }
> +
> + return max_errors;
> +}
> +
> int btrfs_chunk_readonly(struct btrfs_root *root, u64 chunk_offset)
> {
> struct extent_map *em;
> struct map_lookup *map;
> struct btrfs_mapping_tree *map_tree = &root->fs_info->mapping_tree;
> int readonly = 0;
> + int miss_ndevs = 0;
> int i;
>
> read_lock(&map_tree->map_tree.lock);
> @@ -4598,18 +4617,27 @@ int btrfs_chunk_readonly(struct btrfs_root *root, u64 chunk_offset)
> if (!em)
> return 1;
>
> - if (btrfs_test_opt(root, DEGRADED)) {
> - free_extent_map(em);
> - return 0;
> - }
> -
> map = (struct map_lookup *)em->bdev;
> for (i = 0; i < map->num_stripes; i++) {
> + if (map->stripes[i].dev->missing) {
> + miss_ndevs++;
> + continue;
> + }
> +
> if (!map->stripes[i].dev->writeable) {
> readonly = 1;
> - break;
> + goto end;
> }
> }
> +
> + /*
> + * If the number of missing devices is larger than max errors,
> + * we can not write the data into that chunk successfully, so
> + * set it readonly.
> + */
> + if (miss_ndevs > btrfs_chunk_max_errors(map))
> + readonly = 1;
> +end:
> free_extent_map(em);
> return readonly;
> }
> @@ -5220,16 +5248,8 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info, int rw,
> }
> }
>
> - if (rw & (REQ_WRITE | REQ_GET_READ_MIRRORS)) {
> - if (map->type & (BTRFS_BLOCK_GROUP_RAID1 |
> - BTRFS_BLOCK_GROUP_RAID10 |
> - BTRFS_BLOCK_GROUP_RAID5 |
> - BTRFS_BLOCK_GROUP_DUP)) {
> - max_errors = 1;
> - } else if (map->type & BTRFS_BLOCK_GROUP_RAID6) {
> - max_errors = 2;
> - }
> - }
> + if (rw & (REQ_WRITE | REQ_GET_READ_MIRRORS))
> + max_errors = btrfs_chunk_max_errors(map);
>
> if (dev_replace_is_ongoing && (rw & (REQ_WRITE | REQ_DISCARD)) &&
> dev_replace->tgtdev != NULL) {
> --
> 1.9.3
>
> --
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