Revision 774a1221e862b343388347bac9b318767336b20b authored by Tejun Heo on 16 January 2013, 02:52:51 UTC, committed by Linus Torvalds on 16 January 2013, 17:05:33 UTC
If the default iosched is built as module, the kernel may deadlock while trying to load the iosched module on device probe if the probing was running off async. This is because async_synchronize_full() at the end of module init ends up waiting for the async job which initiated the module loading. async A modprobe 1. finds a device 2. registers the block device 3. request_module(default iosched) 4. modprobe in userland 5. load and init module 6. async_synchronize_full() Async A waits for modprobe to finish in request_module() and modprobe waits for async A to finish in async_synchronize_full(). Because there's no easy to track dependency once control goes out to userland, implementing properly nested flushing is difficult. For now, make module init perform async_synchronize_full() iff module init has queued async jobs as suggested by Linus. This avoids the described deadlock because iosched module doesn't use async and thus wouldn't invoke async_synchronize_full(). This is hacky and incomplete. It will deadlock if async module loading nests; however, this works around the known problem case and seems to be the best of bad options. For more details, please refer to the following thread. http://thread.gmane.org/gmane.linux.kernel/1420814 Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Alex Riesen <raa.lkml@gmail.com> Tested-by: Ming Lei <ming.lei@canonical.com> Tested-by: Alex Riesen <raa.lkml@gmail.com> Cc: Arjan van de Ven <arjan@linux.intel.com> Cc: Jens Axboe <axboe@kernel.dk> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent 406089d
debug_fs.c
/******************************************************************************
*******************************************************************************
**
** Copyright (C) 2005-2009 Red Hat, Inc. All rights reserved.
**
** This copyrighted material is made available to anyone wishing to use,
** modify, copy, or redistribute it subject to the terms and conditions
** of the GNU General Public License v.2.
**
*******************************************************************************
******************************************************************************/
#include <linux/pagemap.h>
#include <linux/seq_file.h>
#include <linux/module.h>
#include <linux/ctype.h>
#include <linux/debugfs.h>
#include <linux/slab.h>
#include "dlm_internal.h"
#include "lock.h"
#define DLM_DEBUG_BUF_LEN 4096
static char debug_buf[DLM_DEBUG_BUF_LEN];
static struct mutex debug_buf_lock;
static struct dentry *dlm_root;
static char *print_lockmode(int mode)
{
switch (mode) {
case DLM_LOCK_IV:
return "--";
case DLM_LOCK_NL:
return "NL";
case DLM_LOCK_CR:
return "CR";
case DLM_LOCK_CW:
return "CW";
case DLM_LOCK_PR:
return "PR";
case DLM_LOCK_PW:
return "PW";
case DLM_LOCK_EX:
return "EX";
default:
return "??";
}
}
static int print_format1_lock(struct seq_file *s, struct dlm_lkb *lkb,
struct dlm_rsb *res)
{
seq_printf(s, "%08x %s", lkb->lkb_id, print_lockmode(lkb->lkb_grmode));
if (lkb->lkb_status == DLM_LKSTS_CONVERT ||
lkb->lkb_status == DLM_LKSTS_WAITING)
seq_printf(s, " (%s)", print_lockmode(lkb->lkb_rqmode));
if (lkb->lkb_nodeid) {
if (lkb->lkb_nodeid != res->res_nodeid)
seq_printf(s, " Remote: %3d %08x", lkb->lkb_nodeid,
lkb->lkb_remid);
else
seq_printf(s, " Master: %08x", lkb->lkb_remid);
}
if (lkb->lkb_wait_type)
seq_printf(s, " wait_type: %d", lkb->lkb_wait_type);
return seq_printf(s, "\n");
}
static int print_format1(struct dlm_rsb *res, struct seq_file *s)
{
struct dlm_lkb *lkb;
int i, lvblen = res->res_ls->ls_lvblen, recover_list, root_list;
int rv;
lock_rsb(res);
rv = seq_printf(s, "\nResource %p Name (len=%d) \"",
res, res->res_length);
if (rv)
goto out;
for (i = 0; i < res->res_length; i++) {
if (isprint(res->res_name[i]))
seq_printf(s, "%c", res->res_name[i]);
else
seq_printf(s, "%c", '.');
}
if (res->res_nodeid > 0)
rv = seq_printf(s, "\" \nLocal Copy, Master is node %d\n",
res->res_nodeid);
else if (res->res_nodeid == 0)
rv = seq_printf(s, "\" \nMaster Copy\n");
else if (res->res_nodeid == -1)
rv = seq_printf(s, "\" \nLooking up master (lkid %x)\n",
res->res_first_lkid);
else
rv = seq_printf(s, "\" \nInvalid master %d\n",
res->res_nodeid);
if (rv)
goto out;
/* Print the LVB: */
if (res->res_lvbptr) {
seq_printf(s, "LVB: ");
for (i = 0; i < lvblen; i++) {
if (i == lvblen / 2)
seq_printf(s, "\n ");
seq_printf(s, "%02x ",
(unsigned char) res->res_lvbptr[i]);
}
if (rsb_flag(res, RSB_VALNOTVALID))
seq_printf(s, " (INVALID)");
rv = seq_printf(s, "\n");
if (rv)
goto out;
}
root_list = !list_empty(&res->res_root_list);
recover_list = !list_empty(&res->res_recover_list);
if (root_list || recover_list) {
rv = seq_printf(s, "Recovery: root %d recover %d flags %lx "
"count %d\n", root_list, recover_list,
res->res_flags, res->res_recover_locks_count);
if (rv)
goto out;
}
/* Print the locks attached to this resource */
seq_printf(s, "Granted Queue\n");
list_for_each_entry(lkb, &res->res_grantqueue, lkb_statequeue) {
rv = print_format1_lock(s, lkb, res);
if (rv)
goto out;
}
seq_printf(s, "Conversion Queue\n");
list_for_each_entry(lkb, &res->res_convertqueue, lkb_statequeue) {
rv = print_format1_lock(s, lkb, res);
if (rv)
goto out;
}
seq_printf(s, "Waiting Queue\n");
list_for_each_entry(lkb, &res->res_waitqueue, lkb_statequeue) {
rv = print_format1_lock(s, lkb, res);
if (rv)
goto out;
}
if (list_empty(&res->res_lookup))
goto out;
seq_printf(s, "Lookup Queue\n");
list_for_each_entry(lkb, &res->res_lookup, lkb_rsb_lookup) {
rv = seq_printf(s, "%08x %s", lkb->lkb_id,
print_lockmode(lkb->lkb_rqmode));
if (lkb->lkb_wait_type)
seq_printf(s, " wait_type: %d", lkb->lkb_wait_type);
rv = seq_printf(s, "\n");
}
out:
unlock_rsb(res);
return rv;
}
static int print_format2_lock(struct seq_file *s, struct dlm_lkb *lkb,
struct dlm_rsb *r)
{
u64 xid = 0;
u64 us;
int rv;
if (lkb->lkb_flags & DLM_IFL_USER) {
if (lkb->lkb_ua)
xid = lkb->lkb_ua->xid;
}
/* microseconds since lkb was added to current queue */
us = ktime_to_us(ktime_sub(ktime_get(), lkb->lkb_timestamp));
/* id nodeid remid pid xid exflags flags sts grmode rqmode time_us
r_nodeid r_len r_name */
rv = seq_printf(s, "%x %d %x %u %llu %x %x %d %d %d %llu %u %d \"%s\"\n",
lkb->lkb_id,
lkb->lkb_nodeid,
lkb->lkb_remid,
lkb->lkb_ownpid,
(unsigned long long)xid,
lkb->lkb_exflags,
lkb->lkb_flags,
lkb->lkb_status,
lkb->lkb_grmode,
lkb->lkb_rqmode,
(unsigned long long)us,
r->res_nodeid,
r->res_length,
r->res_name);
return rv;
}
static int print_format2(struct dlm_rsb *r, struct seq_file *s)
{
struct dlm_lkb *lkb;
int rv = 0;
lock_rsb(r);
list_for_each_entry(lkb, &r->res_grantqueue, lkb_statequeue) {
rv = print_format2_lock(s, lkb, r);
if (rv)
goto out;
}
list_for_each_entry(lkb, &r->res_convertqueue, lkb_statequeue) {
rv = print_format2_lock(s, lkb, r);
if (rv)
goto out;
}
list_for_each_entry(lkb, &r->res_waitqueue, lkb_statequeue) {
rv = print_format2_lock(s, lkb, r);
if (rv)
goto out;
}
out:
unlock_rsb(r);
return rv;
}
static int print_format3_lock(struct seq_file *s, struct dlm_lkb *lkb,
int rsb_lookup)
{
u64 xid = 0;
int rv;
if (lkb->lkb_flags & DLM_IFL_USER) {
if (lkb->lkb_ua)
xid = lkb->lkb_ua->xid;
}
rv = seq_printf(s, "lkb %x %d %x %u %llu %x %x %d %d %d %d %d %d %u %llu %llu\n",
lkb->lkb_id,
lkb->lkb_nodeid,
lkb->lkb_remid,
lkb->lkb_ownpid,
(unsigned long long)xid,
lkb->lkb_exflags,
lkb->lkb_flags,
lkb->lkb_status,
lkb->lkb_grmode,
lkb->lkb_rqmode,
lkb->lkb_last_bast.mode,
rsb_lookup,
lkb->lkb_wait_type,
lkb->lkb_lvbseq,
(unsigned long long)ktime_to_ns(lkb->lkb_timestamp),
(unsigned long long)ktime_to_ns(lkb->lkb_last_bast_time));
return rv;
}
static int print_format3(struct dlm_rsb *r, struct seq_file *s)
{
struct dlm_lkb *lkb;
int i, lvblen = r->res_ls->ls_lvblen;
int print_name = 1;
int rv;
lock_rsb(r);
rv = seq_printf(s, "rsb %p %d %x %lx %d %d %u %d ",
r,
r->res_nodeid,
r->res_first_lkid,
r->res_flags,
!list_empty(&r->res_root_list),
!list_empty(&r->res_recover_list),
r->res_recover_locks_count,
r->res_length);
if (rv)
goto out;
for (i = 0; i < r->res_length; i++) {
if (!isascii(r->res_name[i]) || !isprint(r->res_name[i]))
print_name = 0;
}
seq_printf(s, "%s", print_name ? "str " : "hex");
for (i = 0; i < r->res_length; i++) {
if (print_name)
seq_printf(s, "%c", r->res_name[i]);
else
seq_printf(s, " %02x", (unsigned char)r->res_name[i]);
}
rv = seq_printf(s, "\n");
if (rv)
goto out;
if (!r->res_lvbptr)
goto do_locks;
seq_printf(s, "lvb %u %d", r->res_lvbseq, lvblen);
for (i = 0; i < lvblen; i++)
seq_printf(s, " %02x", (unsigned char)r->res_lvbptr[i]);
rv = seq_printf(s, "\n");
if (rv)
goto out;
do_locks:
list_for_each_entry(lkb, &r->res_grantqueue, lkb_statequeue) {
rv = print_format3_lock(s, lkb, 0);
if (rv)
goto out;
}
list_for_each_entry(lkb, &r->res_convertqueue, lkb_statequeue) {
rv = print_format3_lock(s, lkb, 0);
if (rv)
goto out;
}
list_for_each_entry(lkb, &r->res_waitqueue, lkb_statequeue) {
rv = print_format3_lock(s, lkb, 0);
if (rv)
goto out;
}
list_for_each_entry(lkb, &r->res_lookup, lkb_rsb_lookup) {
rv = print_format3_lock(s, lkb, 1);
if (rv)
goto out;
}
out:
unlock_rsb(r);
return rv;
}
static int print_format4(struct dlm_rsb *r, struct seq_file *s)
{
int our_nodeid = dlm_our_nodeid();
int print_name = 1;
int i, rv;
lock_rsb(r);
rv = seq_printf(s, "rsb %p %d %d %d %d %lu %lx %d ",
r,
r->res_nodeid,
r->res_master_nodeid,
r->res_dir_nodeid,
our_nodeid,
r->res_toss_time,
r->res_flags,
r->res_length);
if (rv)
goto out;
for (i = 0; i < r->res_length; i++) {
if (!isascii(r->res_name[i]) || !isprint(r->res_name[i]))
print_name = 0;
}
seq_printf(s, "%s", print_name ? "str " : "hex");
for (i = 0; i < r->res_length; i++) {
if (print_name)
seq_printf(s, "%c", r->res_name[i]);
else
seq_printf(s, " %02x", (unsigned char)r->res_name[i]);
}
rv = seq_printf(s, "\n");
out:
unlock_rsb(r);
return rv;
}
struct rsbtbl_iter {
struct dlm_rsb *rsb;
unsigned bucket;
int format;
int header;
};
/* seq_printf returns -1 if the buffer is full, and 0 otherwise.
If the buffer is full, seq_printf can be called again, but it
does nothing and just returns -1. So, the these printing routines
periodically check the return value to avoid wasting too much time
trying to print to a full buffer. */
static int table_seq_show(struct seq_file *seq, void *iter_ptr)
{
struct rsbtbl_iter *ri = iter_ptr;
int rv = 0;
switch (ri->format) {
case 1:
rv = print_format1(ri->rsb, seq);
break;
case 2:
if (ri->header) {
seq_printf(seq, "id nodeid remid pid xid exflags "
"flags sts grmode rqmode time_ms "
"r_nodeid r_len r_name\n");
ri->header = 0;
}
rv = print_format2(ri->rsb, seq);
break;
case 3:
if (ri->header) {
seq_printf(seq, "version rsb 1.1 lvb 1.1 lkb 1.1\n");
ri->header = 0;
}
rv = print_format3(ri->rsb, seq);
break;
case 4:
if (ri->header) {
seq_printf(seq, "version 4 rsb 2\n");
ri->header = 0;
}
rv = print_format4(ri->rsb, seq);
break;
}
return rv;
}
static const struct seq_operations format1_seq_ops;
static const struct seq_operations format2_seq_ops;
static const struct seq_operations format3_seq_ops;
static const struct seq_operations format4_seq_ops;
static void *table_seq_start(struct seq_file *seq, loff_t *pos)
{
struct rb_root *tree;
struct rb_node *node;
struct dlm_ls *ls = seq->private;
struct rsbtbl_iter *ri;
struct dlm_rsb *r;
loff_t n = *pos;
unsigned bucket, entry;
int toss = (seq->op == &format4_seq_ops);
bucket = n >> 32;
entry = n & ((1LL << 32) - 1);
if (bucket >= ls->ls_rsbtbl_size)
return NULL;
ri = kzalloc(sizeof(struct rsbtbl_iter), GFP_NOFS);
if (!ri)
return NULL;
if (n == 0)
ri->header = 1;
if (seq->op == &format1_seq_ops)
ri->format = 1;
if (seq->op == &format2_seq_ops)
ri->format = 2;
if (seq->op == &format3_seq_ops)
ri->format = 3;
if (seq->op == &format4_seq_ops)
ri->format = 4;
tree = toss ? &ls->ls_rsbtbl[bucket].toss : &ls->ls_rsbtbl[bucket].keep;
spin_lock(&ls->ls_rsbtbl[bucket].lock);
if (!RB_EMPTY_ROOT(tree)) {
for (node = rb_first(tree); node; node = rb_next(node)) {
r = rb_entry(node, struct dlm_rsb, res_hashnode);
if (!entry--) {
dlm_hold_rsb(r);
ri->rsb = r;
ri->bucket = bucket;
spin_unlock(&ls->ls_rsbtbl[bucket].lock);
return ri;
}
}
}
spin_unlock(&ls->ls_rsbtbl[bucket].lock);
/*
* move to the first rsb in the next non-empty bucket
*/
/* zero the entry */
n &= ~((1LL << 32) - 1);
while (1) {
bucket++;
n += 1LL << 32;
if (bucket >= ls->ls_rsbtbl_size) {
kfree(ri);
return NULL;
}
tree = toss ? &ls->ls_rsbtbl[bucket].toss : &ls->ls_rsbtbl[bucket].keep;
spin_lock(&ls->ls_rsbtbl[bucket].lock);
if (!RB_EMPTY_ROOT(tree)) {
node = rb_first(tree);
r = rb_entry(node, struct dlm_rsb, res_hashnode);
dlm_hold_rsb(r);
ri->rsb = r;
ri->bucket = bucket;
spin_unlock(&ls->ls_rsbtbl[bucket].lock);
*pos = n;
return ri;
}
spin_unlock(&ls->ls_rsbtbl[bucket].lock);
}
}
static void *table_seq_next(struct seq_file *seq, void *iter_ptr, loff_t *pos)
{
struct dlm_ls *ls = seq->private;
struct rsbtbl_iter *ri = iter_ptr;
struct rb_root *tree;
struct rb_node *next;
struct dlm_rsb *r, *rp;
loff_t n = *pos;
unsigned bucket;
int toss = (seq->op == &format4_seq_ops);
bucket = n >> 32;
/*
* move to the next rsb in the same bucket
*/
spin_lock(&ls->ls_rsbtbl[bucket].lock);
rp = ri->rsb;
next = rb_next(&rp->res_hashnode);
if (next) {
r = rb_entry(next, struct dlm_rsb, res_hashnode);
dlm_hold_rsb(r);
ri->rsb = r;
spin_unlock(&ls->ls_rsbtbl[bucket].lock);
dlm_put_rsb(rp);
++*pos;
return ri;
}
spin_unlock(&ls->ls_rsbtbl[bucket].lock);
dlm_put_rsb(rp);
/*
* move to the first rsb in the next non-empty bucket
*/
/* zero the entry */
n &= ~((1LL << 32) - 1);
while (1) {
bucket++;
n += 1LL << 32;
if (bucket >= ls->ls_rsbtbl_size) {
kfree(ri);
return NULL;
}
tree = toss ? &ls->ls_rsbtbl[bucket].toss : &ls->ls_rsbtbl[bucket].keep;
spin_lock(&ls->ls_rsbtbl[bucket].lock);
if (!RB_EMPTY_ROOT(tree)) {
next = rb_first(tree);
r = rb_entry(next, struct dlm_rsb, res_hashnode);
dlm_hold_rsb(r);
ri->rsb = r;
ri->bucket = bucket;
spin_unlock(&ls->ls_rsbtbl[bucket].lock);
*pos = n;
return ri;
}
spin_unlock(&ls->ls_rsbtbl[bucket].lock);
}
}
static void table_seq_stop(struct seq_file *seq, void *iter_ptr)
{
struct rsbtbl_iter *ri = iter_ptr;
if (ri) {
dlm_put_rsb(ri->rsb);
kfree(ri);
}
}
static const struct seq_operations format1_seq_ops = {
.start = table_seq_start,
.next = table_seq_next,
.stop = table_seq_stop,
.show = table_seq_show,
};
static const struct seq_operations format2_seq_ops = {
.start = table_seq_start,
.next = table_seq_next,
.stop = table_seq_stop,
.show = table_seq_show,
};
static const struct seq_operations format3_seq_ops = {
.start = table_seq_start,
.next = table_seq_next,
.stop = table_seq_stop,
.show = table_seq_show,
};
static const struct seq_operations format4_seq_ops = {
.start = table_seq_start,
.next = table_seq_next,
.stop = table_seq_stop,
.show = table_seq_show,
};
static const struct file_operations format1_fops;
static const struct file_operations format2_fops;
static const struct file_operations format3_fops;
static const struct file_operations format4_fops;
static int table_open(struct inode *inode, struct file *file)
{
struct seq_file *seq;
int ret = -1;
if (file->f_op == &format1_fops)
ret = seq_open(file, &format1_seq_ops);
else if (file->f_op == &format2_fops)
ret = seq_open(file, &format2_seq_ops);
else if (file->f_op == &format3_fops)
ret = seq_open(file, &format3_seq_ops);
else if (file->f_op == &format4_fops)
ret = seq_open(file, &format4_seq_ops);
if (ret)
return ret;
seq = file->private_data;
seq->private = inode->i_private; /* the dlm_ls */
return 0;
}
static const struct file_operations format1_fops = {
.owner = THIS_MODULE,
.open = table_open,
.read = seq_read,
.llseek = seq_lseek,
.release = seq_release
};
static const struct file_operations format2_fops = {
.owner = THIS_MODULE,
.open = table_open,
.read = seq_read,
.llseek = seq_lseek,
.release = seq_release
};
static const struct file_operations format3_fops = {
.owner = THIS_MODULE,
.open = table_open,
.read = seq_read,
.llseek = seq_lseek,
.release = seq_release
};
static const struct file_operations format4_fops = {
.owner = THIS_MODULE,
.open = table_open,
.read = seq_read,
.llseek = seq_lseek,
.release = seq_release
};
/*
* dump lkb's on the ls_waiters list
*/
static ssize_t waiters_read(struct file *file, char __user *userbuf,
size_t count, loff_t *ppos)
{
struct dlm_ls *ls = file->private_data;
struct dlm_lkb *lkb;
size_t len = DLM_DEBUG_BUF_LEN, pos = 0, ret, rv;
mutex_lock(&debug_buf_lock);
mutex_lock(&ls->ls_waiters_mutex);
memset(debug_buf, 0, sizeof(debug_buf));
list_for_each_entry(lkb, &ls->ls_waiters, lkb_wait_reply) {
ret = snprintf(debug_buf + pos, len - pos, "%x %d %d %s\n",
lkb->lkb_id, lkb->lkb_wait_type,
lkb->lkb_nodeid, lkb->lkb_resource->res_name);
if (ret >= len - pos)
break;
pos += ret;
}
mutex_unlock(&ls->ls_waiters_mutex);
rv = simple_read_from_buffer(userbuf, count, ppos, debug_buf, pos);
mutex_unlock(&debug_buf_lock);
return rv;
}
static const struct file_operations waiters_fops = {
.owner = THIS_MODULE,
.open = simple_open,
.read = waiters_read,
.llseek = default_llseek,
};
void dlm_delete_debug_file(struct dlm_ls *ls)
{
if (ls->ls_debug_rsb_dentry)
debugfs_remove(ls->ls_debug_rsb_dentry);
if (ls->ls_debug_waiters_dentry)
debugfs_remove(ls->ls_debug_waiters_dentry);
if (ls->ls_debug_locks_dentry)
debugfs_remove(ls->ls_debug_locks_dentry);
if (ls->ls_debug_all_dentry)
debugfs_remove(ls->ls_debug_all_dentry);
if (ls->ls_debug_toss_dentry)
debugfs_remove(ls->ls_debug_toss_dentry);
}
int dlm_create_debug_file(struct dlm_ls *ls)
{
char name[DLM_LOCKSPACE_LEN+8];
/* format 1 */
ls->ls_debug_rsb_dentry = debugfs_create_file(ls->ls_name,
S_IFREG | S_IRUGO,
dlm_root,
ls,
&format1_fops);
if (!ls->ls_debug_rsb_dentry)
goto fail;
/* format 2 */
memset(name, 0, sizeof(name));
snprintf(name, DLM_LOCKSPACE_LEN+8, "%s_locks", ls->ls_name);
ls->ls_debug_locks_dentry = debugfs_create_file(name,
S_IFREG | S_IRUGO,
dlm_root,
ls,
&format2_fops);
if (!ls->ls_debug_locks_dentry)
goto fail;
/* format 3 */
memset(name, 0, sizeof(name));
snprintf(name, DLM_LOCKSPACE_LEN+8, "%s_all", ls->ls_name);
ls->ls_debug_all_dentry = debugfs_create_file(name,
S_IFREG | S_IRUGO,
dlm_root,
ls,
&format3_fops);
if (!ls->ls_debug_all_dentry)
goto fail;
/* format 4 */
memset(name, 0, sizeof(name));
snprintf(name, DLM_LOCKSPACE_LEN+8, "%s_toss", ls->ls_name);
ls->ls_debug_toss_dentry = debugfs_create_file(name,
S_IFREG | S_IRUGO,
dlm_root,
ls,
&format4_fops);
if (!ls->ls_debug_toss_dentry)
goto fail;
memset(name, 0, sizeof(name));
snprintf(name, DLM_LOCKSPACE_LEN+8, "%s_waiters", ls->ls_name);
ls->ls_debug_waiters_dentry = debugfs_create_file(name,
S_IFREG | S_IRUGO,
dlm_root,
ls,
&waiters_fops);
if (!ls->ls_debug_waiters_dentry)
goto fail;
return 0;
fail:
dlm_delete_debug_file(ls);
return -ENOMEM;
}
int __init dlm_register_debugfs(void)
{
mutex_init(&debug_buf_lock);
dlm_root = debugfs_create_dir("dlm", NULL);
return dlm_root ? 0 : -ENOMEM;
}
void dlm_unregister_debugfs(void)
{
debugfs_remove(dlm_root);
}
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