On Mon, Nov 04, 2013 at 11:45:43AM +0800, Anand Jain wrote:
> need fsinfo from btrfs-control that is when mount path is
> not known.
> current method of going through each mount points isn't
> efficient, and multiple subvol of a fsid could be mounted
> means extra logic to handle that. Further this will help
> to revamp check_mounted() (planned)
>
> check_mounted is heavily used in the btrfs-progs, it
> does full scan of all the disks in the system to confirm
> if a multi-disk btrfs is mounted it doesn't scalable well
> with few hundreds luns, check_mounted for sure needs a
> revamp. using this it can be done easily. which is planned.
>
> v2: commit reword
>
> Signed-off-by: Anand Jain <anand.jain@xxxxxxxxxx>
> ---
> ioctl.h | 19 +++++++++++++++
> utils.c | 80 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> utils.h | 1 +
> 3 files changed, 100 insertions(+), 0 deletions(-)
>
> diff --git a/ioctl.h b/ioctl.h
> index d21413f..29575d8 100644
> --- a/ioctl.h
> +++ b/ioctl.h
> @@ -506,6 +506,23 @@ static inline char *btrfs_err_str(enum btrfs_err_code err_code)
> }
> }
>
> +/* fs flags */
> +#define BTRFS_FS_MOUNTED (1LLU << 0)
> +
> +struct btrfs_ioctl_fslist {
> + __u64 self_sz; /* in/out */
> + __u8 fsid[BTRFS_FSID_SIZE]; /* out */
> + __u64 num_devices;
> + __u64 missing_devices;
> + __u64 total_devices;
> + __u64 flags;
> +};
> +
> +struct btrfs_ioctl_fslist_args {
> + __u64 self_sz; /* in/out */
> + __u64 count; /* out */
> +};
> +
> #define BTRFS_IOC_SNAP_CREATE _IOW(BTRFS_IOCTL_MAGIC, 1, \
> struct btrfs_ioctl_vol_args)
> #define BTRFS_IOC_DEFRAG _IOW(BTRFS_IOCTL_MAGIC, 2, \
> @@ -604,6 +621,8 @@ struct btrfs_ioctl_clone_range_args {
> struct btrfs_ioctl_dev_replace_args)
> #define BTRFS_IOC_DEDUP_CTL _IOWR(BTRFS_IOCTL_MAGIC, 55, \
> struct btrfs_ioctl_dedup_args)
> +#define BTRFS_IOC_GET_FSLIST _IOWR(BTRFS_IOCTL_MAGIC, 56, \
> + struct btrfs_ioctl_fslist_args)
> #ifdef __cplusplus
> }
> #endif
> diff --git a/utils.c b/utils.c
> index 5bedd97..1798a7c 100644
> --- a/utils.c
> +++ b/utils.c
> @@ -2087,3 +2087,83 @@ int lookup_ino_rootid(int fd, u64 *rootid)
>
> return 0;
> }
> +
> +/* scans for fsid(s) in the kernel using the btrfs-control
> + * interface.
> + */
> +int get_fslist(struct btrfs_ioctl_fslist **out_fslist, int *out_count)
> +{
> + int ret, fd, e;
> + struct btrfs_ioctl_fslist_args *fsargs;
> + struct btrfs_ioctl_fslist *fslist;
> + struct btrfs_ioctl_fslist *fslist_tmp;
> + u64 sz;
> + int count;
> +
> + fd = open("/dev/btrfs-control", O_RDWR);
> + e = errno;
> + if (fd < 0) {
> + perror("failed to open /dev/btrfs-control");
> + return -e;
> + }
> +
> + /* space to hold 512 fsids, doesn't matter if small
> + * it would fail and return count so then we try again
> + */
> + count = 512;
> +again:
> + sz = sizeof(*fsargs) + sizeof(*fslist) * count;
> +
> + fsargs = (struct btrfs_ioctl_fslist_args *) malloc(sz);
No need to cast the return value of malloc.
> + memset(fsargs, 0, sz);
> +
> + if (!fsargs) {
> + close(fd);
> + return -ENOMEM;
> + }
Should check !fsargs before memsetting it.
> + fsargs->count = count;
> +
> + ret = ioctl(fd, BTRFS_IOC_GET_FSLIST, fsargs);
> + e = errno;
> + if (ret == 1) {
> + /* out of size so reallocate */
> + count = fsargs->count;
> + free(fsargs);
> + goto again;
> + } else if (ret < 0) {
> + printf("ERROR: scan_fsid ioctl failed - %s\n",
> + strerror(e));
> + ret = -e;
> + goto out;
> + }
> +
> + /* ioctl returns fsid count in count parameter*/
> +
> + *out_count = count = fsargs->count;
> + if (count == 0) {
> + *out_fslist = NULL;
> + ret = 0;
> + goto out;
> + }
> +
> + fslist = (struct btrfs_ioctl_fslist *) (fsargs +
> + sizeof(*fsargs));
> +
> + fslist_tmp = *out_fslist = (struct btrfs_ioctl_fslist *)
> + malloc(sizeof(*fslist) * count);
No need to cast. Thanks,
Josef
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