On 03/09/2017 09:34 AM, 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 <quwen...@cn.fujitsu.com>
Signed-off-by: Anand Jain <anand.j...@oracle.com>
Tested-by: Austin S. Hemmelgarn <ahferro...@gmail.com>
Tested-by: Adam Borowski <kilob...@angband.pl>
Tested-by: Dmitrii Tcvetkov <demfl...@demfloro.ru>
---
fs/btrfs/volumes.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
fs/btrfs/volumes.h | 1 +
2 files changed, 56 insertions(+)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 73d56eef5e60..83613955e3c2 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -6765,6 +6765,61 @@ 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 the fs is OK to be mounted degraded read-write
+ * Return false if the fs is not OK to be mounted degraded
+ */
+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 = (struct map_lookup *) em->bdev;
any idea why not map = em->map_lookup; here?
Thanks, Anand
+ 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 = 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;
+}
+
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 59be81206dd7..db1b5ef479cf 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -538,4 +538,5 @@ 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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