btrfs-progs: Introduce function to get correct stripe length

Introduce a new function, btrfs_get_chunk_stripe_len() to get correct
stripe length.
This is very handy for lowmem mode, which checks the mapping between
device extent and chunk item.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/volumes.c b/volumes.c
index fdc3a94..990300f 100644 (file)
--- a/volumes.c
+++ b/volumes.c
@@ -2287,3 +2287,47 @@ out:
 
        return ret;
 }
+
+/*
+ * Get stripe length from chunk item and its stripe items
+ *
+ * Caller should only call this function after validating the chunk item
+ * by using btrfs_check_chunk_valid().
+ */
+u64 btrfs_stripe_length(struct btrfs_fs_info *fs_info,
+                       struct extent_buffer *leaf,
+                       struct btrfs_chunk *chunk)
+{
+       u64 stripe_len;
+       u64 chunk_len;
+       u32 num_stripes = btrfs_chunk_num_stripes(leaf, chunk);
+       u64 profile = btrfs_chunk_type(leaf, chunk) &
+                     BTRFS_BLOCK_GROUP_PROFILE_MASK;
+
+       chunk_len = btrfs_chunk_length(leaf, chunk);
+
+       switch (profile) {
+       case 0: /* Single profile */
+       case BTRFS_BLOCK_GROUP_RAID1:
+       case BTRFS_BLOCK_GROUP_DUP:
+               stripe_len = chunk_len;
+               break;
+       case BTRFS_BLOCK_GROUP_RAID0:
+               stripe_len = chunk_len / num_stripes;
+               break;
+       case BTRFS_BLOCK_GROUP_RAID5:
+               stripe_len = chunk_len / (num_stripes - 1);
+               break;
+       case BTRFS_BLOCK_GROUP_RAID6:
+               stripe_len = chunk_len / (num_stripes - 2);
+               break;
+       case BTRFS_BLOCK_GROUP_RAID10:
+               stripe_len = chunk_len / (num_stripes /
+                               btrfs_chunk_sub_stripes(leaf, chunk));
+               break;
+       default:
+               /* Invalid chunk profile found */
+               BUG_ON(1);
+       }
+       return stripe_len;
+}

diff --git a/volumes.h b/volumes.h
index 699b0ba..fc0a775 100644 (file)
--- a/volumes.h
+++ b/volumes.h
@@ -246,4 +246,7 @@ int btrfs_check_chunk_valid(struct btrfs_root *root,
                            struct extent_buffer *leaf,
                            struct btrfs_chunk *chunk,
                            int slot, u64 logical);
+u64 btrfs_stripe_length(struct btrfs_fs_info *fs_info,
+                       struct extent_buffer *leaf,
+                       struct btrfs_chunk *chunk);
 #endif