Re: [PATCH 27/33] extension of IncrementalRemove to store location (port) of removed device

[Neil Brown <neilb@suse.de>]

On Mon, 5 Jul 2010 10:40:54 +0100
"Czarnowska, Anna" <anna.czarnowska@intel.com> wrote:

> From: Przemyslaw Czarnowski <przemyslaw.hawrylewicz.czarnowski@intel.com>
> 
> 
> 
> If the disk is taken out from its port this port information is lost. Only udev rule can provide us with this information, and then we have to store it somehow. This patch adds writing 'cookie' file in /var/run/mdadm directory in form of file named with value of <path-id>, containing the names of arrays holding this device before it was removed.
> 
> FAILED_SLOTS constant has been added to hold the location of cookie files.
> 
> 
> 
> Signed-off-by: Przemyslaw Czarnowski <przemyslaw.hawrylewicz.czarnowski@intel.com<mailto:przemyslaw.hawrylewicz.czarnowski@intel.com>>
> 
> ---
> 
>  Incremental.c |   63 ++++++++++++++++++++++++++++++++++++++++++++++++++++----
> 
>  Makefile      |    6 +++-
> 
>  mdadm.h       |    8 +++++++
> 
>  3 files changed, 70 insertions(+), 7 deletions(-)
> 
> 
> 
> diff --git a/Incremental.c b/Incremental.c index 20e3445..adaefb9 100644
> 
> --- a/Incremental.c
> 
> +++ b/Incremental.c
> 
> @@ -937,19 +937,22 @@ int Incremental_container(struct supertype *st, char *devname, int verbose,
> 
>   * raid arrays, and if so first fail (if needed) and then remove the device.
> 
>   *
> 
>   * @devname - The device we want to remove
> 
> + * @id_path - name as found in /dev/disk/by-path for this device
> 
>   *
> 
>   * Note: the device name must be a kernel name like "sda", so
> 
>   * that we can find it in /proc/mdstat
> 
>   */
> 
> -int IncrementalRemove(char *devname, char *path, int verbose)
> 
> +int IncrementalRemove(char *devname, char *id_path, int verbose)
> 
>  {
> 
>       int mdfd;
> 
>       int rv;
> 
> -     struct mdstat_ent *ent;
> 
> +     struct mdstat_ent *ent, *mds, *mi;
> 
>       struct mddev_dev_s devlist;
> 
> +     char path[PATH_MAX];
> 
> +     FILE *id_fd;
> 
> 
> 
> -     if (!path) {
> 
> -           fprintf(stderr, Name ": incremental removal without --path <path_id> lacks "
> 
> +     if (!id_path) {
> 
> +           fprintf(stderr, Name ": incremental removal without --path <id_path> lacks "
> 
>                   "the possibility to re-add new device in this port\n");
> 
>             return 1;
> 
>       }
> 
> @@ -965,15 +968,65 @@ int IncrementalRemove(char *devname, char *path, int verbose)
> 
>                   "of any array\n", devname);
> 
>             return 1;
> 
>       }
> 
> +     strncpy(path, FAILED_SLOTS, PATH_MAX);
> 
> +     if (mkdir(path, O_CREAT) < 0 && errno != EEXIST) {

It is incorrect to path O_CREAT to mkdir.
It should be permission bits such as '0700' or S_IRWXU.

Also, the strncpy is pointless, just use
    mkdir(FAILED_SLOTS, 0700)


> 
> +           fprintf(stderr, Name ": can't create file to save path to old disk\n");
> 
> +           return 1;
> 
> +     }
> 
> +     snprintf(path, PATH_MAX, FAILED_SLOTS "/%s", id_path);
> 
> +
> 
> +     if ((id_fd = fopen(path, "w")) == NULL) {
> 
> +           fprintf(stderr, Name ": can't create file to save path to old disk\n");
> 
> +           return 1;
> 
> +     }

Again, I don't think it is reasonably to failed the "-If" just because you
cannot record the removal.


> 
> -     Manage_subdevs(ent->dev, mdfd, &devlist, verbose);
> 
> +
> 
> +     /* slightly different behavior for native and external */
> 
> +     if (!is_external(ent->metadata_version)) {
> 
> +           /* just write array device */
> 
> +           if (fprintf(id_fd, "%s\n", ent->dev) < 0) {
> 
> +                 fprintf(stderr, Name ": Failed to write to <id_path> cookie\n");
> 
> +                 fclose(id_fd);
> 
> +                 unlink(path);
> 
> +           }

Do we really want to record the array as "md0" or "md127" ??

I would have thought we would record the uuid, probably together with the
metadata type to ensure no ambiguity if some time passes before plugging a
new device in.
We may even want to let the metadata handler provide a string to save and
later restore.

Or on the other hand, do we need to record anything other than "this device
was using in an md array" which tells is that it is appropriate for md to
grab any device that is plugged in.
Once a device has been taken for use by md, it should surely be put to the
best use based on what the various policies allow, should it not?
i.e. exactly the same slot in the same array is not necessary is it?
(and if it is, then we would need to record the slot number, and I don't
think you do).


> 
> +#ifndef FAILED_SLOTS
> 
> +#define FAILED_SLOTS "/var/run/failed-slots"
> 
> +#endif /* FAILED_SLOTS */
> 

This should be in /var/run/mdadm/ somewhere.
e.g. /var/run/mdadm/failed-slots.

NeilBrown