I happened to pass swap partition as root partition in cmdline,
then kernel panic and tell me about "Cannot open root device".
It is not correct, in fact it is a fs type mismatch instead of 'no device'.
Eventually I found btrfs mounting failed with -EIO, it should be -EINVAL.
The logic in init/do_mounts.c:
for (p = fs_names; *p; p += strlen(p)+1) {
int err = do_mount_root(name, p, flags, root_mount_data);
switch (err) {
case 0:
goto out;
case -EACCES:
flags |= MS_RDONLY;
goto retry;
case -EINVAL:
continue;
}
print "Cannot open root device"
panic
}
SO fs type after btrfs will have no chance to mount
Here fix the return value as -EINVAL
Signed-off-by: Dave Young <hidave.darks...@gmail.com>
---
fs/btrfs/disk-io.c | 4 +++-
fs/btrfs/volumes.c | 8 +++++---
2 files changed, 8 insertions(+), 4 deletions(-)
--- linux-2.6.orig/fs/btrfs/disk-io.c 2010-12-29 21:53:17.473333338 +0800
+++ linux-2.6/fs/btrfs/disk-io.c 2010-12-29 21:57:37.916666672 +0800
@@ -1713,8 +1713,10 @@ struct btrfs_root *open_ctree(struct sup
fs_info, BTRFS_ROOT_TREE_OBJECTID);
bh = btrfs_read_dev_super(fs_devices->latest_bdev);
- if (!bh)
+ if (!bh) {
+ err = -EINVAL;
goto fail_iput;
+ }
memcpy(&fs_info->super_copy, bh->b_data, sizeof(fs_info->super_copy));
memcpy(&fs_info->super_for_commit, &fs_info->super_copy,
--- linux-2.6.orig/fs/btrfs/volumes.c 2010-12-29 21:53:17.503333338 +0800
+++ linux-2.6/fs/btrfs/volumes.c 2010-12-29 21:57:37.920000005 +0800
@@ -598,8 +598,10 @@ static int __btrfs_open_devices(struct b
set_blocksize(bdev, 4096);
bh = btrfs_read_dev_super(bdev);
- if (!bh)
+ if (!bh) {
+ ret = -EINVAL;
goto error_close;
+ }
disk_super = (struct btrfs_super_block *)bh->b_data;
devid = btrfs_stack_device_id(&disk_super->dev_item);
@@ -700,7 +702,7 @@ int btrfs_scan_one_device(const char *pa
goto error_close;
bh = btrfs_read_dev_super(bdev);
if (!bh) {
- ret = -EIO;
+ ret = -EINVAL;
goto error_close;
}
disk_super = (struct btrfs_super_block *)bh->b_data;
@@ -1193,7 +1195,7 @@ int btrfs_rm_device(struct btrfs_root *r
set_blocksize(bdev, 4096);
bh = btrfs_read_dev_super(bdev);
if (!bh) {
- ret = -EIO;
+ ret = -EINVAL;
goto error_close;
}
disk_super = (struct btrfs_super_block *)bh->b_data;
--
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