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 | 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
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