fs: btrfs: Do not fail when all root_backups are empty
This is the case when reading freshly created filesystem.
The error message is like the following:
btrfs_read_superblock: No valid root_backup found!
Since the data from super_roots/root_backups is not actually used -
decided to rework btrfs_newest_root_backup() into
btrfs_check_super_roots() that will only check if super_roots
array is valid and correctly handle empty scenario.
As a result:
* btrfs_read_superblock() now only checks if super_roots array is valid;
the case when it is empty is considered OK.
* removed root_backup pointer from btrfs_info,
which would be NULL in case of empty super_roots.
* btrfs_read_superblock() verifies number of devices from the superblock
itself, not newest root_backup.
Signed-off-by: Yevgeny Popovych <yevgenyp@pointgrab.com>
Cc: Marek Behun <marek.behun@nic.cz>
Cc: Sergey Struzh <sergeys@pointgrab.com>
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index ad6641f..e680caa 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -15,18 +15,34 @@
#define BTRFS_SUPER_INFO_SIZE 4096
-static int btrfs_newest_root_backup(struct btrfs_super_block *sb)
+/*
+ * checks if a valid root backup is present.
+ * considers the case when all root backups empty valid.
+ * returns -1 in case of invalid root backup and 0 for valid.
+ */
+static int btrfs_check_super_roots(struct btrfs_super_block *sb)
{
struct btrfs_root_backup *root_backup;
int i, newest = -1;
+ int num_empty = 0;
for (i = 0; i < BTRFS_NUM_BACKUP_ROOTS; ++i) {
root_backup = sb->super_roots + i;
+
+ if (root_backup->tree_root == 0 && root_backup->tree_root_gen == 0)
+ num_empty++;
+
if (root_backup->tree_root_gen == sb->generation)
newest = i;
}
- return newest;
+ if (num_empty == BTRFS_NUM_BACKUP_ROOTS) {
+ return 0;
+ } else if (newest >= 0) {
+ return 0;
+ }
+
+ return -1;
}
static inline int is_power_of_2(u64 x)
@@ -166,7 +182,7 @@
char raw_sb[BTRFS_SUPER_INFO_SIZE];
struct btrfs_super_block *sb = (struct btrfs_super_block *) raw_sb;
u64 dev_total_bytes;
- int i, root_backup_idx;
+ int i;
dev_total_bytes = (u64) btrfs_part_info->size * btrfs_part_info->blksz;
@@ -211,17 +227,15 @@
return -1;
}
- root_backup_idx = btrfs_newest_root_backup(&btrfs_info.sb);
- if (root_backup_idx < 0) {
+ if (btrfs_check_super_roots(&btrfs_info.sb)) {
printf("%s: No valid root_backup found!\n", __func__);
return -1;
}
- btrfs_info.root_backup = btrfs_info.sb.super_roots + root_backup_idx;
- if (btrfs_info.root_backup->num_devices != 1) {
+ if (btrfs_info.sb.num_devices != 1) {
printf("%s: Unsupported number of devices (%lli). This driver "
"only supports filesystem on one device.\n", __func__,
- btrfs_info.root_backup->num_devices);
+ btrfs_info.sb.num_devices);
return -1;
}