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Btrfs: add DEVICE_READY ioctl 

This will be used in conjunction with btrfs device ready <dev>.  This is
needed for initrd's to have a nice and lightweight way to tell if all of the
devices needed for a file system are in the cache currently.  This keeps
them from having to do mount+sleep loops waiting for devices to show up.
Thanks,

Signed-off-by: Josef Bacik <jbacik@fusionio.com>
This commit is contained in:
Josef Bacik 2012-06-21 16:03:58 -04:00 committed by Chris Mason
parent 96c3f4331a
commit 02db0844be
4 changed files with 18 additions and 2 deletions
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3
fs/btrfs/ioctl.h
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@ -363,7 +363,8 @@ struct btrfs_ioctl_get_dev_stats {
struct btrfs_ioctl_ino_path_args)
#define BTRFS_IOC_LOGICAL_INO _IOWR(BTRFS_IOCTL_MAGIC, 36, \
struct btrfs_ioctl_ino_path_args)
#define BTRFS_IOC_DEVICES_READY _IOR(BTRFS_IOCTL_MAGIC, 39, \
struct btrfs_ioctl_vol_args)
#define BTRFS_IOC_GET_DEV_STATS _IOWR(BTRFS_IOCTL_MAGIC, 52, \
struct btrfs_ioctl_get_dev_stats)
#endif

7
fs/btrfs/super.c
View File

@ -1462,6 +1462,13 @@ static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
ret = btrfs_scan_one_device(vol->name, FMODE_READ,
&btrfs_fs_type, &fs_devices);
break;
case BTRFS_IOC_DEVICES_READY:
ret = btrfs_scan_one_device(vol->name, FMODE_READ,
&btrfs_fs_type, &fs_devices);
if (ret)
break;
ret = !(fs_devices->num_devices == fs_devices->total_devices);
break;
}
kfree(vol);

9
fs/btrfs/volumes.c
View File

@ -429,6 +429,7 @@ static struct btrfs_fs_devices *clone_fs_devices(struct btrfs_fs_devices *orig)
mutex_init(&fs_devices->device_list_mutex);
fs_devices->latest_devid = orig->latest_devid;
fs_devices->latest_trans = orig->latest_trans;
fs_devices->total_devices = orig->total_devices;
memcpy(fs_devices->fsid, orig->fsid, sizeof(fs_devices->fsid));
/* We have held the volume lock, it is safe to get the devices. */
@ -739,6 +740,7 @@ int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
int ret;
u64 devid;
u64 transid;
u64 total_devices;
flags |= FMODE_EXCL;
bdev = blkdev_get_by_path(path, flags, holder);
@ -760,6 +762,7 @@ int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
disk_super = (struct btrfs_super_block *)bh->b_data;
devid = btrfs_stack_device_id(&disk_super->dev_item);
transid = btrfs_super_generation(disk_super);
total_devices = btrfs_super_num_devices(disk_super);
if (disk_super->label[0])
printk(KERN_INFO "device label %s ", disk_super->label);
else
@ -767,7 +770,8 @@ int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
printk(KERN_CONT "devid %llu transid %llu %s\n",
(unsigned long long)devid, (unsigned long long)transid, path);
ret = device_list_add(path, disk_super, devid, fs_devices_ret);
if (!ret && fs_devices_ret)
(*fs_devices_ret)->total_devices = total_devices;
brelse(bh);
error_close:
mutex_unlock(&uuid_mutex);
@ -1433,6 +1437,7 @@ int btrfs_rm_device(struct btrfs_root *root, char *device_path)
list_del_rcu(&device->dev_list);
device->fs_devices->num_devices--;
device->fs_devices->total_devices--;
if (device->missing)
root->fs_info->fs_devices->missing_devices--;
@ -1550,6 +1555,7 @@ static int btrfs_prepare_sprout(struct btrfs_root *root)
fs_devices->seeding = 0;
fs_devices->num_devices = 0;
fs_devices->open_devices = 0;
fs_devices->total_devices = 0;
fs_devices->seed = seed_devices;
generate_random_uuid(fs_devices->fsid);
@ -1749,6 +1755,7 @@ int btrfs_init_new_device(struct btrfs_root *root, char *device_path)
root->fs_info->fs_devices->num_devices++;
root->fs_info->fs_devices->open_devices++;
root->fs_info->fs_devices->rw_devices++;
root->fs_info->fs_devices->total_devices++;
if (device->can_discard)
root->fs_info->fs_devices->num_can_discard++;
root->fs_info->fs_devices->total_rw_bytes += device->total_bytes;

1
fs/btrfs/volumes.h
View File

@ -126,6 +126,7 @@ struct btrfs_fs_devices {
u64 missing_devices;
u64 total_rw_bytes;
u64 num_can_discard;
u64 total_devices;
struct block_device *latest_bdev;
/* all of the devices in the FS, protected by a mutex