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. This patch depends on the btrfs kernel patch btrfs: add framework to read fs info from btrfs-control Signed-off-by: Anand Jain <anand.j...@oracle.com> --- v5: edits commit message v4: bug fix and accepts Stefan suggested v3: accepts Josef suggested v2: commit reword ioctl.h | 19 ++++++++++++++++ utils.c | 75 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ utils.h | 1 + 3 files changed, 95 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 c1c55db..1ed7cde 100644 --- a/utils.c +++ b/utils.c @@ -47,6 +47,7 @@ #include "utils.h" #include "volumes.h" #include "ioctl.h" +#include "btrfs-list.h" #ifndef BLKDISCARD #define BLKDISCARD _IO(0x12,119) @@ -2111,3 +2112,77 @@ 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, u64 *out_count) +{ + int ret, fd, e; + struct btrfs_ioctl_fslist_args *fsargs; + struct btrfs_ioctl_fslist_args *fsargs_saved = NULL; + struct btrfs_ioctl_fslist *fslist; + 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_saved = fsargs = malloc(sz); + if (!fsargs) { + close(fd); + return -ENOMEM; + } + + memset(fsargs, 0, sz); + 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 = fsargs->count; + if (*out_count == 0) { + *out_fslist = NULL; + ret = 0; + goto out; + } + + fslist = (struct btrfs_ioctl_fslist *) (++fsargs); + + sz = sizeof(*fslist) * *out_count; + *out_fslist = malloc(sz); + if (*out_fslist == NULL) { + ret = -ENOMEM; + goto out; + } + memcpy(*out_fslist, fslist, sz); + ret = 0; +out: + free(fsargs_saved); + close(fd); + return ret; +} diff --git a/utils.h b/utils.h index 512c51b..2fc230b 100644 --- a/utils.h +++ b/utils.h @@ -96,5 +96,6 @@ int ask_user(char *question); int lookup_ino_rootid(int fd, u64 *rootid); int btrfs_scan_lblkid(int update_kernel); int get_btrfs_mount(const char *dev, char *mp, size_t mp_size); +int get_fslist(struct btrfs_ioctl_fslist **out_fslist, u64 *out_count); #endif -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html