Commit 2f232036 authored by Jan Schmidt's avatar Jan Schmidt Committed by Josef Bacik

Btrfs: rescan for qgroups

If qgroup tracking is out of sync, a rescan operation can be started. It
iterates the complete extent tree and recalculates all qgroup tracking data.
This is an expensive operation and should not be used unless required.

A filesystem under rescan can still be umounted. The rescan continues on the
next mount.  Status information is provided with a separate ioctl while a
rescan operation is in progress.
Signed-off-by: default avatarJan Schmidt <list.btrfs@jan-o-sch.net>
Signed-off-by: default avatarJosef Bacik <jbacik@fusionio.com>
parent 46b665ce
......@@ -1021,9 +1021,9 @@ struct btrfs_block_group_item {
*/
#define BTRFS_QGROUP_STATUS_FLAG_ON (1ULL << 0)
/*
* SCANNING is set during the initialization phase
* RESCAN is set during the initialization phase
*/
#define BTRFS_QGROUP_STATUS_FLAG_SCANNING (1ULL << 1)
#define BTRFS_QGROUP_STATUS_FLAG_RESCAN (1ULL << 1)
/*
* Some qgroup entries are known to be out of date,
* either because the configuration has changed in a way that
......@@ -1052,7 +1052,7 @@ struct btrfs_qgroup_status_item {
* only used during scanning to record the progress
* of the scan. It contains a logical address
*/
__le64 scan;
__le64 rescan;
} __attribute__ ((__packed__));
struct btrfs_qgroup_info_item {
......@@ -1603,6 +1603,11 @@ struct btrfs_fs_info {
/* used by btrfs_qgroup_record_ref for an efficient tree traversal */
u64 qgroup_seq;
/* qgroup rescan items */
struct mutex qgroup_rescan_lock; /* protects the progress item */
struct btrfs_key qgroup_rescan_progress;
struct btrfs_workers qgroup_rescan_workers;
/* filesystem state */
unsigned long fs_state;
......@@ -2886,8 +2891,8 @@ BTRFS_SETGET_FUNCS(qgroup_status_version, struct btrfs_qgroup_status_item,
version, 64);
BTRFS_SETGET_FUNCS(qgroup_status_flags, struct btrfs_qgroup_status_item,
flags, 64);
BTRFS_SETGET_FUNCS(qgroup_status_scan, struct btrfs_qgroup_status_item,
scan, 64);
BTRFS_SETGET_FUNCS(qgroup_status_rescan, struct btrfs_qgroup_status_item,
rescan, 64);
/* btrfs_qgroup_info_item */
BTRFS_SETGET_FUNCS(qgroup_info_generation, struct btrfs_qgroup_info_item,
......@@ -3828,7 +3833,7 @@ int btrfs_quota_enable(struct btrfs_trans_handle *trans,
struct btrfs_fs_info *fs_info);
int btrfs_quota_disable(struct btrfs_trans_handle *trans,
struct btrfs_fs_info *fs_info);
int btrfs_quota_rescan(struct btrfs_fs_info *fs_info);
int btrfs_qgroup_rescan(struct btrfs_fs_info *fs_info);
int btrfs_add_qgroup_relation(struct btrfs_trans_handle *trans,
struct btrfs_fs_info *fs_info, u64 src, u64 dst);
int btrfs_del_qgroup_relation(struct btrfs_trans_handle *trans,
......
......@@ -1976,6 +1976,7 @@ static void btrfs_stop_all_workers(struct btrfs_fs_info *fs_info)
btrfs_stop_workers(&fs_info->caching_workers);
btrfs_stop_workers(&fs_info->readahead_workers);
btrfs_stop_workers(&fs_info->flush_workers);
btrfs_stop_workers(&fs_info->qgroup_rescan_workers);
}
/* helper to cleanup tree roots */
......@@ -2267,6 +2268,7 @@ int open_ctree(struct super_block *sb,
fs_info->qgroup_seq = 1;
fs_info->quota_enabled = 0;
fs_info->pending_quota_state = 0;
mutex_init(&fs_info->qgroup_rescan_lock);
btrfs_init_free_cluster(&fs_info->meta_alloc_cluster);
btrfs_init_free_cluster(&fs_info->data_alloc_cluster);
......@@ -2476,6 +2478,8 @@ int open_ctree(struct super_block *sb,
btrfs_init_workers(&fs_info->readahead_workers, "readahead",
fs_info->thread_pool_size,
&fs_info->generic_worker);
btrfs_init_workers(&fs_info->qgroup_rescan_workers, "qgroup-rescan", 1,
&fs_info->generic_worker);
/*
* endios are largely parallel and should have a very
......@@ -2510,6 +2514,7 @@ int open_ctree(struct super_block *sb,
ret |= btrfs_start_workers(&fs_info->caching_workers);
ret |= btrfs_start_workers(&fs_info->readahead_workers);
ret |= btrfs_start_workers(&fs_info->flush_workers);
ret |= btrfs_start_workers(&fs_info->qgroup_rescan_workers);
if (ret) {
err = -ENOMEM;
goto fail_sb_buffer;
......
......@@ -3701,12 +3701,10 @@ static long btrfs_ioctl_quota_ctl(struct file *file, void __user *arg)
}
down_write(&root->fs_info->subvol_sem);
if (sa->cmd != BTRFS_QUOTA_CTL_RESCAN) {
trans = btrfs_start_transaction(root->fs_info->tree_root, 2);
if (IS_ERR(trans)) {
ret = PTR_ERR(trans);
goto out;
}
trans = btrfs_start_transaction(root->fs_info->tree_root, 2);
if (IS_ERR(trans)) {
ret = PTR_ERR(trans);
goto out;
}
switch (sa->cmd) {
......@@ -3716,9 +3714,6 @@ static long btrfs_ioctl_quota_ctl(struct file *file, void __user *arg)
case BTRFS_QUOTA_CTL_DISABLE:
ret = btrfs_quota_disable(trans, root->fs_info);
break;
case BTRFS_QUOTA_CTL_RESCAN:
ret = btrfs_quota_rescan(root->fs_info);
break;
default:
ret = -EINVAL;
break;
......@@ -3727,11 +3722,9 @@ static long btrfs_ioctl_quota_ctl(struct file *file, void __user *arg)
if (copy_to_user(arg, sa, sizeof(*sa)))
ret = -EFAULT;
if (trans) {
err = btrfs_commit_transaction(trans, root->fs_info->tree_root);
if (err && !ret)
ret = err;
}
err = btrfs_commit_transaction(trans, root->fs_info->tree_root);
if (err && !ret)
ret = err;
out:
kfree(sa);
up_write(&root->fs_info->subvol_sem);
......@@ -3886,6 +3879,64 @@ static long btrfs_ioctl_qgroup_limit(struct file *file, void __user *arg)
return ret;
}
static long btrfs_ioctl_quota_rescan(struct file *file, void __user *arg)
{
struct btrfs_root *root = BTRFS_I(fdentry(file)->d_inode)->root;
struct btrfs_ioctl_quota_rescan_args *qsa;
int ret;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
ret = mnt_want_write_file(file);
if (ret)
return ret;
qsa = memdup_user(arg, sizeof(*qsa));
if (IS_ERR(qsa)) {
ret = PTR_ERR(qsa);
goto drop_write;
}
if (qsa->flags) {
ret = -EINVAL;
goto out;
}
ret = btrfs_qgroup_rescan(root->fs_info);
out:
kfree(qsa);
drop_write:
mnt_drop_write_file(file);
return ret;
}
static long btrfs_ioctl_quota_rescan_status(struct file *file, void __user *arg)
{
struct btrfs_root *root = BTRFS_I(fdentry(file)->d_inode)->root;
struct btrfs_ioctl_quota_rescan_args *qsa;
int ret = 0;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
qsa = kzalloc(sizeof(*qsa), GFP_NOFS);
if (!qsa)
return -ENOMEM;
if (root->fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_RESCAN) {
qsa->flags = 1;
qsa->progress = root->fs_info->qgroup_rescan_progress.objectid;
}
if (copy_to_user(arg, qsa, sizeof(*qsa)))
ret = -EFAULT;
kfree(qsa);
return ret;
}
static long btrfs_ioctl_set_received_subvol(struct file *file,
void __user *arg)
{
......@@ -4124,6 +4175,10 @@ long btrfs_ioctl(struct file *file, unsigned int
return btrfs_ioctl_qgroup_create(file, argp);
case BTRFS_IOC_QGROUP_LIMIT:
return btrfs_ioctl_qgroup_limit(file, argp);
case BTRFS_IOC_QUOTA_RESCAN:
return btrfs_ioctl_quota_rescan(file, argp);
case BTRFS_IOC_QUOTA_RESCAN_STATUS:
return btrfs_ioctl_quota_rescan_status(file, argp);
case BTRFS_IOC_DEV_REPLACE:
return btrfs_ioctl_dev_replace(root, argp);
case BTRFS_IOC_GET_FSLABEL:
......
......@@ -31,13 +31,13 @@
#include "locking.h"
#include "ulist.h"
#include "backref.h"
#include "extent_io.h"
/* TODO XXX FIXME
* - subvol delete -> delete when ref goes to 0? delete limits also?
* - reorganize keys
* - compressed
* - sync
* - rescan
* - copy also limits on subvol creation
* - limit
* - caches fuer ulists
......@@ -98,6 +98,14 @@ struct btrfs_qgroup_list {
struct btrfs_qgroup *member;
};
struct qgroup_rescan {
struct btrfs_work work;
struct btrfs_fs_info *fs_info;
};
static void qgroup_rescan_start(struct btrfs_fs_info *fs_info,
struct qgroup_rescan *qscan);
/* must be called with qgroup_ioctl_lock held */
static struct btrfs_qgroup *find_qgroup_rb(struct btrfs_fs_info *fs_info,
u64 qgroupid)
......@@ -298,7 +306,20 @@ int btrfs_read_qgroup_config(struct btrfs_fs_info *fs_info)
}
fs_info->qgroup_flags = btrfs_qgroup_status_flags(l,
ptr);
/* FIXME read scan element */
fs_info->qgroup_rescan_progress.objectid =
btrfs_qgroup_status_rescan(l, ptr);
if (fs_info->qgroup_flags &
BTRFS_QGROUP_STATUS_FLAG_RESCAN) {
struct qgroup_rescan *qscan =
kmalloc(sizeof(*qscan), GFP_NOFS);
if (!qscan) {
ret = -ENOMEM;
goto out;
}
fs_info->qgroup_rescan_progress.type = 0;
fs_info->qgroup_rescan_progress.offset = 0;
qgroup_rescan_start(fs_info, qscan);
}
goto next1;
}
......@@ -719,7 +740,8 @@ static int update_qgroup_status_item(struct btrfs_trans_handle *trans,
ptr = btrfs_item_ptr(l, slot, struct btrfs_qgroup_status_item);
btrfs_set_qgroup_status_flags(l, ptr, fs_info->qgroup_flags);
btrfs_set_qgroup_status_generation(l, ptr, trans->transid);
/* XXX scan */
btrfs_set_qgroup_status_rescan(l, ptr,
fs_info->qgroup_rescan_progress.objectid);
btrfs_mark_buffer_dirty(l);
......@@ -830,7 +852,7 @@ int btrfs_quota_enable(struct btrfs_trans_handle *trans,
fs_info->qgroup_flags = BTRFS_QGROUP_STATUS_FLAG_ON |
BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
btrfs_set_qgroup_status_flags(leaf, ptr, fs_info->qgroup_flags);
btrfs_set_qgroup_status_scan(leaf, ptr, 0);
btrfs_set_qgroup_status_rescan(leaf, ptr, 0);
btrfs_mark_buffer_dirty(leaf);
......@@ -944,10 +966,11 @@ int btrfs_quota_disable(struct btrfs_trans_handle *trans,
return ret;
}
int btrfs_quota_rescan(struct btrfs_fs_info *fs_info)
static void qgroup_dirty(struct btrfs_fs_info *fs_info,
struct btrfs_qgroup *qgroup)
{
/* FIXME */
return 0;
if (list_empty(&qgroup->dirty))
list_add(&qgroup->dirty, &fs_info->dirty_qgroups);
}
int btrfs_add_qgroup_relation(struct btrfs_trans_handle *trans,
......@@ -1155,13 +1178,6 @@ int btrfs_limit_qgroup(struct btrfs_trans_handle *trans,
return ret;
}
static void qgroup_dirty(struct btrfs_fs_info *fs_info,
struct btrfs_qgroup *qgroup)
{
if (list_empty(&qgroup->dirty))
list_add(&qgroup->dirty, &fs_info->dirty_qgroups);
}
/*
* btrfs_qgroup_record_ref is called when the ref is added or deleted. it puts
* the modification into a list that's later used by btrfs_end_transaction to
......@@ -1390,6 +1406,15 @@ int btrfs_qgroup_account_ref(struct btrfs_trans_handle *trans,
BUG();
}
mutex_lock(&fs_info->qgroup_rescan_lock);
if (fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_RESCAN) {
if (fs_info->qgroup_rescan_progress.objectid <= node->bytenr) {
mutex_unlock(&fs_info->qgroup_rescan_lock);
return 0;
}
}
mutex_unlock(&fs_info->qgroup_rescan_lock);
/*
* the delayed ref sequence number we pass depends on the direction of
* the operation. for add operations, we pass
......@@ -1403,7 +1428,15 @@ int btrfs_qgroup_account_ref(struct btrfs_trans_handle *trans,
if (ret < 0)
return ret;
mutex_lock(&fs_info->qgroup_rescan_lock);
spin_lock(&fs_info->qgroup_lock);
if (fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_RESCAN) {
if (fs_info->qgroup_rescan_progress.objectid <= node->bytenr) {
ret = 0;
goto unlock;
}
}
quota_root = fs_info->quota_root;
if (!quota_root)
goto unlock;
......@@ -1445,6 +1478,7 @@ int btrfs_qgroup_account_ref(struct btrfs_trans_handle *trans,
unlock:
spin_unlock(&fs_info->qgroup_lock);
mutex_unlock(&fs_info->qgroup_rescan_lock);
ulist_free(roots);
ulist_free(tmp);
......@@ -1823,3 +1857,259 @@ void assert_qgroups_uptodate(struct btrfs_trans_handle *trans)
(u32)trans->delayed_ref_elem.seq);
BUG();
}
/*
* returns < 0 on error, 0 when more leafs are to be scanned.
* returns 1 when done, 2 when done and FLAG_INCONSISTENT was cleared.
*/
static int
qgroup_rescan_leaf(struct qgroup_rescan *qscan, struct btrfs_path *path,
struct btrfs_trans_handle *trans, struct ulist *tmp,
struct extent_buffer *scratch_leaf)
{
struct btrfs_key found;
struct btrfs_fs_info *fs_info = qscan->fs_info;
struct ulist *roots = NULL;
struct ulist_node *unode;
struct ulist_iterator uiter;
struct seq_list tree_mod_seq_elem = {};
u64 seq;
int slot;
int ret;
path->leave_spinning = 1;
mutex_lock(&fs_info->qgroup_rescan_lock);
ret = btrfs_search_slot_for_read(fs_info->extent_root,
&fs_info->qgroup_rescan_progress,
path, 1, 0);
pr_debug("current progress key (%llu %u %llu), search_slot ret %d\n",
(unsigned long long)fs_info->qgroup_rescan_progress.objectid,
fs_info->qgroup_rescan_progress.type,
(unsigned long long)fs_info->qgroup_rescan_progress.offset,
ret);
if (ret) {
/*
* The rescan is about to end, we will not be scanning any
* further blocks. We cannot unset the RESCAN flag here, because
* we want to commit the transaction if everything went well.
* To make the live accounting work in this phase, we set our
* scan progress pointer such that every real extent objectid
* will be smaller.
*/
fs_info->qgroup_rescan_progress.objectid = (u64)-1;
btrfs_release_path(path);
mutex_unlock(&fs_info->qgroup_rescan_lock);
return ret;
}
btrfs_item_key_to_cpu(path->nodes[0], &found,
btrfs_header_nritems(path->nodes[0]) - 1);
fs_info->qgroup_rescan_progress.objectid = found.objectid + 1;
btrfs_get_tree_mod_seq(fs_info, &tree_mod_seq_elem);
memcpy(scratch_leaf, path->nodes[0], sizeof(*scratch_leaf));
slot = path->slots[0];
btrfs_release_path(path);
mutex_unlock(&fs_info->qgroup_rescan_lock);
for (; slot < btrfs_header_nritems(scratch_leaf); ++slot) {
btrfs_item_key_to_cpu(scratch_leaf, &found, slot);
if (found.type != BTRFS_EXTENT_ITEM_KEY)
continue;
ret = btrfs_find_all_roots(trans, fs_info, found.objectid,
tree_mod_seq_elem.seq, &roots);
if (ret < 0)
goto out;
spin_lock(&fs_info->qgroup_lock);
seq = fs_info->qgroup_seq;
fs_info->qgroup_seq += roots->nnodes + 1; /* max refcnt */
ret = qgroup_account_ref_step1(fs_info, roots, tmp, seq);
if (ret) {
spin_unlock(&fs_info->qgroup_lock);
ulist_free(roots);
goto out;
}
/*
* step2 of btrfs_qgroup_account_ref works from a single root,
* we're doing all at once here.
*/
ulist_reinit(tmp);
ULIST_ITER_INIT(&uiter);
while ((unode = ulist_next(roots, &uiter))) {
struct btrfs_qgroup *qg;
qg = find_qgroup_rb(fs_info, unode->val);
if (!qg)
continue;
ret = ulist_add(tmp, qg->qgroupid, (uintptr_t)qg,
GFP_ATOMIC);
if (ret < 0) {
spin_unlock(&fs_info->qgroup_lock);
ulist_free(roots);
goto out;
}
}
/* this loop is similar to step 2 of btrfs_qgroup_account_ref */
ULIST_ITER_INIT(&uiter);
while ((unode = ulist_next(tmp, &uiter))) {
struct btrfs_qgroup *qg;
struct btrfs_qgroup_list *glist;
qg = (struct btrfs_qgroup *)(uintptr_t) unode->aux;
qg->rfer += found.offset;
qg->rfer_cmpr += found.offset;
WARN_ON(qg->tag >= seq);
if (qg->refcnt - seq == roots->nnodes) {
qg->excl += found.offset;
qg->excl_cmpr += found.offset;
}
qgroup_dirty(fs_info, qg);
list_for_each_entry(glist, &qg->groups, next_group) {
ret = ulist_add(tmp, glist->group->qgroupid,
(uintptr_t)glist->group,
GFP_ATOMIC);
if (ret < 0) {
spin_unlock(&fs_info->qgroup_lock);
ulist_free(roots);
goto out;
}
}
}
spin_unlock(&fs_info->qgroup_lock);
ulist_free(roots);
ret = 0;
}
out:
btrfs_put_tree_mod_seq(fs_info, &tree_mod_seq_elem);
return ret;
}
static void btrfs_qgroup_rescan_worker(struct btrfs_work *work)
{
struct qgroup_rescan *qscan = container_of(work, struct qgroup_rescan,
work);
struct btrfs_path *path;
struct btrfs_trans_handle *trans = NULL;
struct btrfs_fs_info *fs_info = qscan->fs_info;
struct ulist *tmp = NULL;
struct extent_buffer *scratch_leaf = NULL;
int err = -ENOMEM;
path = btrfs_alloc_path();
if (!path)
goto out;
tmp = ulist_alloc(GFP_NOFS);
if (!tmp)
goto out;
scratch_leaf = kmalloc(sizeof(*scratch_leaf), GFP_NOFS);
if (!scratch_leaf)
goto out;
err = 0;
while (!err) {
trans = btrfs_start_transaction(fs_info->fs_root, 0);
if (IS_ERR(trans)) {
err = PTR_ERR(trans);
break;
}
if (!fs_info->quota_enabled) {
err = -EINTR;
} else {
err = qgroup_rescan_leaf(qscan, path, trans,
tmp, scratch_leaf);
}
if (err > 0)
btrfs_commit_transaction(trans, fs_info->fs_root);
else
btrfs_end_transaction(trans, fs_info->fs_root);
}
out:
kfree(scratch_leaf);
ulist_free(tmp);
btrfs_free_path(path);
kfree(qscan);
mutex_lock(&fs_info->qgroup_rescan_lock);
fs_info->qgroup_flags &= ~BTRFS_QGROUP_STATUS_FLAG_RESCAN;
if (err == 2 &&
fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT) {
fs_info->qgroup_flags &= ~BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
} else if (err < 0) {
fs_info->qgroup_flags |= BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
}
mutex_unlock(&fs_info->qgroup_rescan_lock);
if (err >= 0) {
pr_info("btrfs: qgroup scan completed%s\n",
err == 2 ? " (inconsistency flag cleared)" : "");
} else {
pr_err("btrfs: qgroup scan failed with %d\n", err);
}
}
static void
qgroup_rescan_start(struct btrfs_fs_info *fs_info, struct qgroup_rescan *qscan)
{
memset(&qscan->work, 0, sizeof(qscan->work));
qscan->work.func = btrfs_qgroup_rescan_worker;
qscan->fs_info = fs_info;
pr_info("btrfs: qgroup scan started\n");
btrfs_queue_worker(&fs_info->qgroup_rescan_workers, &qscan->work);
}
int
btrfs_qgroup_rescan(struct btrfs_fs_info *fs_info)
{
int ret = 0;
struct rb_node *n;
struct btrfs_qgroup *qgroup;
struct qgroup_rescan *qscan = kmalloc(sizeof(*qscan), GFP_NOFS);
if (!qscan)
return -ENOMEM;
mutex_lock(&fs_info->qgroup_rescan_lock);
spin_lock(&fs_info->qgroup_lock);
if (fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_RESCAN)
ret = -EINPROGRESS;
else if (!(fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_ON))
ret = -EINVAL;
if (ret) {
spin_unlock(&fs_info->qgroup_lock);
mutex_unlock(&fs_info->qgroup_rescan_lock);
kfree(qscan);
return ret;
}
fs_info->qgroup_flags |= BTRFS_QGROUP_STATUS_FLAG_RESCAN;
memset(&fs_info->qgroup_rescan_progress, 0,
sizeof(fs_info->qgroup_rescan_progress));
/* clear all current qgroup tracking information */
for (n = rb_first(&fs_info->qgroup_tree); n; n = rb_next(n)) {
qgroup = rb_entry(n, struct btrfs_qgroup, node);
qgroup->rfer = 0;
qgroup->rfer_cmpr = 0;
qgroup->excl = 0;
qgroup->excl_cmpr = 0;
}
spin_unlock(&fs_info->qgroup_lock);
mutex_unlock(&fs_info->qgroup_rescan_lock);
qgroup_rescan_start(fs_info, qscan);
return 0;
}
......@@ -376,12 +376,18 @@ struct btrfs_ioctl_get_dev_stats {
#define BTRFS_QUOTA_CTL_ENABLE 1
#define BTRFS_QUOTA_CTL_DISABLE 2
#define BTRFS_QUOTA_CTL_RESCAN 3
#define BTRFS_QUOTA_CTL_RESCAN__NOTUSED 3
struct btrfs_ioctl_quota_ctl_args {
__u64 cmd;
__u64 status;
};
struct btrfs_ioctl_quota_rescan_args {
__u64 flags;
__u64 progress;
__u64 reserved[6];
};
struct btrfs_ioctl_qgroup_assign_args {
__u64 assign;
__u64 src;
......@@ -520,6 +526,10 @@ struct btrfs_ioctl_send_args {
struct btrfs_ioctl_qgroup_create_args)
#define BTRFS_IOC_QGROUP_LIMIT _IOR(BTRFS_IOCTL_MAGIC, 43, \
struct btrfs_ioctl_qgroup_limit_args)
#define BTRFS_IOC_QUOTA_RESCAN _IOW(BTRFS_IOCTL_MAGIC, 44, \
struct btrfs_ioctl_quota_rescan_args)
#define BTRFS_IOC_QUOTA_RESCAN_STATUS _IOR(BTRFS_IOCTL_MAGIC, 45, \
struct btrfs_ioctl_quota_rescan_args)
#define BTRFS_IOC_GET_FSLABEL _IOR(BTRFS_IOCTL_MAGIC, 49, \
char[BTRFS_LABEL_SIZE])
#define BTRFS_IOC_SET_FSLABEL _IOW(BTRFS_IOCTL_MAGIC, 50, \
......
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