Hi Anand,
Some comments on your kernel patch from a quick jump through:
On 01.11.2012 11:46, Anand jain wrote:
> From: Anand Jain <anand.j...@oracle.com>
>
> This modifies the struct btrfs_root_item to hold the label,
> and make it v3 of this structure.
>
> Signed-off-by: Anand Jain <anand.j...@oracle.com>
> ---
> fs/btrfs/ctree.h | 14 ++++++++++++++
> fs/btrfs/ioctl.c | 32 ++++++++++++++++++++++++++++++++
> fs/btrfs/ioctl.h | 2 ++
> fs/btrfs/root-tree.c | 44 +++++++++++++++++++++++---------------------
> fs/btrfs/transaction.c | 1 +
> 5 files changed, 72 insertions(+), 21 deletions(-)
>
> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> index 994d255..b280256 100644
> --- a/fs/btrfs/ctree.h
> +++ b/fs/btrfs/ctree.h
> @@ -759,6 +759,10 @@ struct btrfs_root_item {
> struct btrfs_timespec otime;
> struct btrfs_timespec stime;
> struct btrfs_timespec rtime;
> +
> + __le64 generation_v3;
What is that supposed to be?
> + char label[BTRFS_LABEL_SIZE]; /* Add label to subvol */
> +
> __le64 reserved[8]; /* for future */
> } __attribute__ ((__packed__));
You can't do that. There's a reason why we've got reserved bytes for
future use. Never change the struct's size.
> @@ -2428,6 +2432,8 @@ BTRFS_SETGET_STACK_FUNCS(root_last_snapshot, struct
> btrfs_root_item,
> last_snapshot, 64);
> BTRFS_SETGET_STACK_FUNCS(root_generation_v2, struct btrfs_root_item,
> generation_v2, 64);
> +BTRFS_SETGET_STACK_FUNCS(root_generation_v3, struct btrfs_root_item,
> + generation_v3, 64);
> BTRFS_SETGET_STACK_FUNCS(root_ctransid, struct btrfs_root_item,
> ctransid, 64);
> BTRFS_SETGET_STACK_FUNCS(root_otransid, struct btrfs_root_item,
> @@ -2441,6 +2447,14 @@ static inline bool btrfs_root_readonly(struct
> btrfs_root *root)
> {
> return (root->root_item.flags & cpu_to_le64(BTRFS_ROOT_SUBVOL_RDONLY))
> != 0;
> }
> +static inline char * btrfs_root_label(struct btrfs_root *root)
> +{
> + return (root->root_item.label);
> +}
> +static inline void btrfs_root_set_label(struct btrfs_root *root, char *val)
> +{
> + memcpy(root->root_item.label,val,BTRFS_LABEL_SIZE);
> +}
>
> /* struct btrfs_root_backup */
> BTRFS_SETGET_STACK_FUNCS(backup_tree_root, struct btrfs_root_backup,
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index e58bd9d..cce0128 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -3725,6 +3725,34 @@ static int btrfs_ioctl_set_label(struct btrfs_root
> *root, void __user *arg)
> return 0;
> }
>
> +static int btrfs_ioctl_subvol_getlabel(struct btrfs_root *root,
> + void __user *arg)
> +{
> + char *label;
> +
> + label = btrfs_root_label(root);
> + if (copy_to_user(arg, label, BTRFS_LABEL_SIZE))
> + return -EFAULT;
> + return 0;
> +}
> +
> +static int btrfs_ioctl_subvol_setlabel(struct btrfs_root *root,
> + void __user *arg)
> +{
> + char label[BTRFS_LABEL_SIZE];
> + struct btrfs_trans_handle *trans;
> +
> + if (copy_from_user(label, arg, BTRFS_LABEL_SIZE))
> + return -EFAULT;
> + trans = btrfs_start_transaction(root, 1);
> + if (IS_ERR(trans))
> + return PTR_ERR(trans);
> + btrfs_root_set_label(root, label);
> + btrfs_commit_transaction(trans, root);
Why use start/commit instead of join/end here?
> + return 0;
> +}
> +
> long btrfs_ioctl(struct file *file, unsigned int
> cmd, unsigned long arg)
> {
> @@ -3827,6 +3855,10 @@ long btrfs_ioctl(struct file *file, unsigned int
> return btrfs_ioctl_get_label(root, argp);
> case BTRFS_IOC_SET_LABEL:
> return btrfs_ioctl_set_label(root, argp);
> + case BTRFS_IOC_SUBVOL_GETLABEL:
> + return btrfs_ioctl_subvol_getlabel(root, argp);
> + case BTRFS_IOC_SUBVOL_SETLABEL:
> + return btrfs_ioctl_subvol_setlabel(root, argp);
> }
>
> return -ENOTTY;
> diff --git a/fs/btrfs/ioctl.h b/fs/btrfs/ioctl.h
> index 0c60fcb..1009a0c 100644
> --- a/fs/btrfs/ioctl.h
> +++ b/fs/btrfs/ioctl.h
> @@ -455,4 +455,6 @@ struct btrfs_ioctl_send_args {
> struct btrfs_ioctl_get_dev_stats)
> #define BTRFS_IOC_GET_LABEL _IOR(BTRFS_IOCTL_MAGIC, 53, __u64)
> #define BTRFS_IOC_SET_LABEL _IOW(BTRFS_IOCTL_MAGIC, 54, __u64)
> +#define BTRFS_IOC_SUBVOL_GETLABEL _IOWR(BTRFS_IOCTL_MAGIC, 55, __u64)
> +#define BTRFS_IOC_SUBVOL_SETLABEL _IOW(BTRFS_IOCTL_MAGIC, 56, __u64)
> #endif
> diff --git a/fs/btrfs/root-tree.c b/fs/btrfs/root-tree.c
> index eb923d0..2a9ae5f 100644
> --- a/fs/btrfs/root-tree.c
> +++ b/fs/btrfs/root-tree.c
> @@ -35,32 +35,34 @@ void btrfs_read_root_item(struct btrfs_root *root,
> {
> uuid_le uuid;
> int len;
> - int need_reset = 0;
>
> len = btrfs_item_size_nr(eb, slot);
> read_extent_buffer(eb, item, btrfs_item_ptr_offset(eb, slot),
> min_t(int, len, (int)sizeof(*item)));
> - if (len < sizeof(*item))
> - need_reset = 1;
> - if (!need_reset && btrfs_root_generation(item)
> - != btrfs_root_generation_v2(item)) {
> - if (btrfs_root_generation_v2(item) != 0) {
> - printk(KERN_WARNING "btrfs: mismatching "
> - "generation and generation_v2 "
> - "found in root item. This root "
> - "was probably mounted with an "
> - "older kernel. Resetting all "
> - "new fields.\n");
Please argue why removing this without replacement should be a good idea.
> - }
> - need_reset = 1;
> - }
> - if (need_reset) {
> - memset(&item->generation_v2, 0,
> - sizeof(*item) - offsetof(struct btrfs_root_item,
> - generation_v2));
>
> - uuid_le_gen(&uuid);
> - memcpy(item->uuid, uuid.b, BTRFS_UUID_SIZE);
> + /* when len is gt sizeof(*item) that means its downgrade and
> + the new members won't be touched anyways
> + if len is lt sizeof(*item) its upgrade, we need to take
> + care to set/reset newer members.
> + */
> + if (len < sizeof(*item)) {
> + /* there is an upgrade need to set/reset the new members
> + assume v1 v2 v3 it can be upgrade from
> + v1 to v2 (set/reset only new members of v2)
> + v2 to v3 (set/reset only new members of v3)
> + v1 to v3 (set/reset new to v1)
> + */
> + if (btrfs_root_generation(item) !=
> btrfs_root_generation_v2(item)) {
> + //memset(&item->generation_v2, 0,
> + //sizeof(*item) - offsetof(struct
> btrfs_root_item, generation_v2));
> + memset(&item->generation_v2, 0, sizeof(*item) - len);
> + uuid_le_gen(&uuid);
> + memcpy(item->uuid, uuid.b, BTRFS_UUID_SIZE);
> + } else if (btrfs_root_generation_v2(item) !=
> btrfs_root_generation_v3(item)) {
> + //memset(&item->generation_v3, 0,
> + // sizeof(*item) - offsetof(struct
> btrfs_root_item, generation_v3));
> + memset(&item->generation_v3, 0, sizeof(*item) - len);
> + }
> }
> }
>
> diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
> index 04bbfb1..45bff43 100644
> --- a/fs/btrfs/transaction.c
> +++ b/fs/btrfs/transaction.c
> @@ -1116,6 +1116,7 @@ static noinline int create_pending_snapshot(struct
> btrfs_trans_handle *trans,
> btrfs_set_root_otransid(new_root_item, trans->transid);
> memset(&new_root_item->stime, 0, sizeof(new_root_item->stime));
> memset(&new_root_item->rtime, 0, sizeof(new_root_item->rtime));
> + memset(new_root_item->label, 0, BTRFS_LABEL_SIZE);
> btrfs_set_root_stransid(new_root_item, 0);
> btrfs_set_root_rtransid(new_root_item, 0);
>
>
-Jan
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