btrfs: Refactor btrfs_check_super_valid

Refactor btrfs_check_super_valid:

1) Rename it to btrfs_validate_mount_super()
   Now it's more obvious when the function should be called.

2) Extract core check routine into validate_super()
   Later write time check can reuse it, and if needed, we could also
   use validate_super() to check each super block.

3) Add more comments about btrfs_validate_mount_super()
   Mostly about what it doesn't check and when it should be called.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ rename to validate_super ]
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 6dff0028d69a900cdc4997faaf09eeb0ce1dd883..eff8673700362bb4a3d679184612b382fbae0328 100644 (file)
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2440,9 +2440,19 @@ out:
        return ret;
 }
 
-static int btrfs_check_super_valid(struct btrfs_fs_info *fs_info)
+/*
+ * Real super block validation
+ * NOTE: super csum type and incompat features will not be checked here.
+ *
+ * @sb:                super block to check
+ * @mirror_num:        the super block number to check its bytenr:
+ *             0       the primary (1st) sb
+ *             1, 2    2nd and 3rd backup copy
+ *            -1       skip bytenr check
+ */
+static int validate_super(struct btrfs_fs_info *fs_info,
+                           struct btrfs_super_block *sb, int mirror_num)
 {
-       struct btrfs_super_block *sb = fs_info->super_copy;
        u64 nodesize = btrfs_super_nodesize(sb);
        u64 sectorsize = btrfs_super_sectorsize(sb);
        int ret = 0;
@@ -2545,7 +2555,8 @@ static int btrfs_check_super_valid(struct btrfs_fs_info *fs_info)
                ret = -EINVAL;
        }
 
-       if (btrfs_super_bytenr(sb) != BTRFS_SUPER_INFO_OFFSET) {
+       if (mirror_num >= 0 &&
+           btrfs_super_bytenr(sb) != btrfs_sb_offset(mirror_num)) {
                btrfs_err(fs_info, "super offset mismatch %llu != %u",
                          btrfs_super_bytenr(sb), BTRFS_SUPER_INFO_OFFSET);
                ret = -EINVAL;
@@ -2589,6 +2600,16 @@ static int btrfs_check_super_valid(struct btrfs_fs_info *fs_info)
        return ret;
 }
 
+/*
+ * Validation of super block at mount time.
+ * Some checks already done early at mount time, like csum type and incompat
+ * flags will be skipped.
+ */
+static int btrfs_validate_mount_super(struct btrfs_fs_info *fs_info)
+{
+       return validate_super(fs_info, fs_info->super_copy, 0);
+}
+
 int open_ctree(struct super_block *sb,
               struct btrfs_fs_devices *fs_devices,
               char *options)
@@ -2814,7 +2835,7 @@ int open_ctree(struct super_block *sb,
 
        memcpy(fs_info->fsid, fs_info->super_copy->fsid, BTRFS_FSID_SIZE);
 
-       ret = btrfs_check_super_valid(fs_info);
+       ret = btrfs_validate_mount_super(fs_info);
        if (ret) {
                btrfs_err(fs_info, "superblock contains fatal errors");
                err = -EINVAL;