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block: create the request_queue debugfs_dir on registration 

We were only creating the request_queue debugfs_dir only
for make_request block drivers (multiqueue), but never for
request-based block drivers. We did this as we were only
creating non-blktrace additional debugfs files on that directory
for make_request drivers. However, since blktrace *always* creates
that directory anyway, we special-case the use of that directory
on blktrace. Other than this being an eye-sore, this exposes
request-based block drivers to the same debugfs fragile
race that used to exist with make_request block drivers
where if we start adding files onto that directory we can later
run a race with a double removal of dentries on the directory
if we don't deal with this carefully on blktrace.

Instead, just simplify things by always creating the request_queue
debugfs_dir on request_queue registration. Rename the mutex also to
reflect the fact that this is used outside of the blktrace context.

Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Luis Chamberlain 2020-06-19 20:47:30 +00:00 committed by Jens Axboe
parent b431ef837e
commit 85e0cbbb8a
6 changed files with 39 additions and 48 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
block/blk-core.c
View File

@ -51,9 +51,7 @@
#include "blk-pm.h"
#include "blk-rq-qos.h"
#ifdef CONFIG_DEBUG_FS
struct dentry *blk_debugfs_root;
#endif
EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_remap);
EXPORT_TRACEPOINT_SYMBOL_GPL(block_rq_remap);
@ -555,9 +553,7 @@ struct request_queue *__blk_alloc_queue(int node_id)
kobject_init(&q->kobj, &blk_queue_ktype);
#ifdef CONFIG_BLK_DEV_IO_TRACE
mutex_init(&q->blk_trace_mutex);
#endif
mutex_init(&q->debugfs_mutex);
mutex_init(&q->sysfs_lock);
mutex_init(&q->sysfs_dir_lock);
spin_lock_init(&q->queue_lock);
@ -1931,9 +1927,7 @@ int __init blk_dev_init(void)
blk_requestq_cachep = kmem_cache_create("request_queue",
sizeof(struct request_queue), 0, SLAB_PANIC, NULL);
#ifdef CONFIG_DEBUG_FS
blk_debugfs_root = debugfs_create_dir("block", NULL);
#endif
return 0;
}

5
block/blk-mq-debugfs.c
View File

@ -824,9 +824,6 @@ void blk_mq_debugfs_register(struct request_queue *q)
struct blk_mq_hw_ctx *hctx;
int i;
q->debugfs_dir = debugfs_create_dir(kobject_name(q->kobj.parent),
blk_debugfs_root);
debugfs_create_files(q->debugfs_dir, q, blk_mq_debugfs_queue_attrs);
/*
@ -857,9 +854,7 @@ void blk_mq_debugfs_register(struct request_queue *q)
void blk_mq_debugfs_unregister(struct request_queue *q)
{
debugfs_remove_recursive(q->debugfs_dir);
q->sched_debugfs_dir = NULL;
q->debugfs_dir = NULL;
}
static void blk_mq_debugfs_register_ctx(struct blk_mq_hw_ctx *hctx,

9
block/blk-sysfs.c
View File

@ -11,6 +11,7 @@
#include <linux/blktrace_api.h>
#include <linux/blk-mq.h>
#include <linux/blk-cgroup.h>
#include <linux/debugfs.h>
#include "blk.h"
#include "blk-mq.h"
@ -917,6 +918,9 @@ static void blk_release_queue(struct kobject *kobj)
blk_mq_release(q);
blk_trace_shutdown(q);
mutex_lock(&q->debugfs_mutex);
debugfs_remove_recursive(q->debugfs_dir);
mutex_unlock(&q->debugfs_mutex);
if (queue_is_mq(q))
blk_mq_debugfs_unregister(q);
@ -989,6 +993,11 @@ int blk_register_queue(struct gendisk *disk)
goto unlock;
}
mutex_lock(&q->debugfs_mutex);
q->debugfs_dir = debugfs_create_dir(kobject_name(q->kobj.parent),
blk_debugfs_root);
mutex_unlock(&q->debugfs_mutex);
if (queue_is_mq(q)) {
__blk_mq_register_dev(dev, q);
blk_mq_debugfs_register(q);

2
block/blk.h
View File

@ -14,9 +14,7 @@
/* Max future timer expiry for timeouts */
#define BLK_MAX_TIMEOUT (5 * HZ)
#ifdef CONFIG_DEBUG_FS
extern struct dentry *blk_debugfs_root;
#endif
struct blk_flush_queue {
unsigned int flush_pending_idx:1;

5
include/linux/blkdev.h
View File

@ -528,9 +528,9 @@ struct request_queue {
unsigned int sg_timeout;
unsigned int sg_reserved_size;
int node;
struct mutex debugfs_mutex;
#ifdef CONFIG_BLK_DEV_IO_TRACE
struct blk_trace __rcu *blk_trace;
struct mutex blk_trace_mutex;
#endif
/*
* for flush operations
@ -574,8 +574,9 @@ struct request_queue {
struct list_head tag_set_list;
struct bio_set bio_split;
#ifdef CONFIG_BLK_DEBUG_FS
struct dentry *debugfs_dir;
#ifdef CONFIG_BLK_DEBUG_FS
struct dentry *sched_debugfs_dir;
struct dentry *rqos_debugfs_dir;
#endif

58
kernel/trace/blktrace.c
View File

@ -348,7 +348,7 @@ static int __blk_trace_remove(struct request_queue *q)
struct blk_trace *bt;
bt = rcu_replace_pointer(q->blk_trace, NULL,
lockdep_is_held(&q->blk_trace_mutex));
lockdep_is_held(&q->debugfs_mutex));
if (!bt)
return -EINVAL;
@ -362,9 +362,9 @@ int blk_trace_remove(struct request_queue *q)
{
int ret;
mutex_lock(&q->blk_trace_mutex);
mutex_lock(&q->debugfs_mutex);
ret = __blk_trace_remove(q);
mutex_unlock(&q->blk_trace_mutex);
mutex_unlock(&q->debugfs_mutex);
return ret;
}
@ -483,14 +483,11 @@ static int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
struct dentry *dir = NULL;
int ret;
lockdep_assert_held(&q->blk_trace_mutex);
lockdep_assert_held(&q->debugfs_mutex);
if (!buts->buf_size || !buts->buf_nr)
return -EINVAL;
if (!blk_debugfs_root)
return -ENOENT;
strncpy(buts->name, name, BLKTRACE_BDEV_SIZE);
buts->name[BLKTRACE_BDEV_SIZE - 1] = '\0';
@ -505,7 +502,7 @@ static int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
* we can be.
*/
if (rcu_dereference_protected(q->blk_trace,
lockdep_is_held(&q->blk_trace_mutex))) {
lockdep_is_held(&q->debugfs_mutex))) {
pr_warn("Concurrent blktraces are not allowed on %s\n",
buts->name);
return -EBUSY;
@ -524,18 +521,15 @@ static int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
if (!bt->msg_data)
goto err;
#ifdef CONFIG_BLK_DEBUG_FS
/*
* When tracing whole make_request drivers (multiqueue) block devices,
* reuse the existing debugfs directory created by the block layer on
* init. For request-based block devices, all partitions block devices,
* When tracing the whole disk reuse the existing debugfs directory
* created by the block layer on init. For partitions block devices,
* and scsi-generic block devices we create a temporary new debugfs
* directory that will be removed once the trace ends.
*/
if (queue_is_mq(q) && bdev && bdev == bdev->bd_contains)
if (bdev && bdev == bdev->bd_contains)
dir = q->debugfs_dir;
else
#endif
bt->dir = dir = debugfs_create_dir(buts->name, blk_debugfs_root);
/*
@ -617,9 +611,9 @@ int blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
{
int ret;
mutex_lock(&q->blk_trace_mutex);
mutex_lock(&q->debugfs_mutex);
ret = __blk_trace_setup(q, name, dev, bdev, arg);
mutex_unlock(&q->blk_trace_mutex);
mutex_unlock(&q->debugfs_mutex);
return ret;
}
@ -665,7 +659,7 @@ static int __blk_trace_startstop(struct request_queue *q, int start)
struct blk_trace *bt;
bt = rcu_dereference_protected(q->blk_trace,
lockdep_is_held(&q->blk_trace_mutex));
lockdep_is_held(&q->debugfs_mutex));
if (bt == NULL)
return -EINVAL;
@ -705,9 +699,9 @@ int blk_trace_startstop(struct request_queue *q, int start)
{
int ret;
mutex_lock(&q->blk_trace_mutex);
mutex_lock(&q->debugfs_mutex);
ret = __blk_trace_startstop(q, start);
mutex_unlock(&q->blk_trace_mutex);
mutex_unlock(&q->debugfs_mutex);
return ret;
}
@ -736,7 +730,7 @@ int blk_trace_ioctl(struct block_device *bdev, unsigned cmd, char __user *arg)
if (!q)
return -ENXIO;
mutex_lock(&q->blk_trace_mutex);
mutex_lock(&q->debugfs_mutex);
switch (cmd) {
case BLKTRACESETUP:
@ -763,7 +757,7 @@ int blk_trace_ioctl(struct block_device *bdev, unsigned cmd, char __user *arg)
break;
}
mutex_unlock(&q->blk_trace_mutex);
mutex_unlock(&q->debugfs_mutex);
return ret;
}
@ -774,14 +768,14 @@ int blk_trace_ioctl(struct block_device *bdev, unsigned cmd, char __user *arg)
**/
void blk_trace_shutdown(struct request_queue *q)
{
mutex_lock(&q->blk_trace_mutex);
mutex_lock(&q->debugfs_mutex);
if (rcu_dereference_protected(q->blk_trace,
lockdep_is_held(&q->blk_trace_mutex))) {
lockdep_is_held(&q->debugfs_mutex))) {
__blk_trace_startstop(q, 0);
__blk_trace_remove(q);
}
mutex_unlock(&q->blk_trace_mutex);
mutex_unlock(&q->debugfs_mutex);
}
#ifdef CONFIG_BLK_CGROUP
@ -1662,7 +1656,7 @@ static int blk_trace_remove_queue(struct request_queue *q)
struct blk_trace *bt;
bt = rcu_replace_pointer(q->blk_trace, NULL,
lockdep_is_held(&q->blk_trace_mutex));
lockdep_is_held(&q->debugfs_mutex));
if (bt == NULL)
return -EINVAL;
@ -1837,10 +1831,10 @@ static ssize_t sysfs_blk_trace_attr_show(struct device *dev,
if (q == NULL)
goto out_bdput;
mutex_lock(&q->blk_trace_mutex);
mutex_lock(&q->debugfs_mutex);
bt = rcu_dereference_protected(q->blk_trace,
lockdep_is_held(&q->blk_trace_mutex));
lockdep_is_held(&q->debugfs_mutex));
if (attr == &dev_attr_enable) {
ret = sprintf(buf, "%u\n", !!bt);
goto out_unlock_bdev;
@ -1858,7 +1852,7 @@ static ssize_t sysfs_blk_trace_attr_show(struct device *dev,
ret = sprintf(buf, "%llu\n", bt->end_lba);
out_unlock_bdev:
mutex_unlock(&q->blk_trace_mutex);
mutex_unlock(&q->debugfs_mutex);
out_bdput:
bdput(bdev);
out:
@ -1901,10 +1895,10 @@ static ssize_t sysfs_blk_trace_attr_store(struct device *dev,
if (q == NULL)
goto out_bdput;
mutex_lock(&q->blk_trace_mutex);
mutex_lock(&q->debugfs_mutex);
bt = rcu_dereference_protected(q->blk_trace,
lockdep_is_held(&q->blk_trace_mutex));
lockdep_is_held(&q->debugfs_mutex));
if (attr == &dev_attr_enable) {
if (!!value == !!bt) {
ret = 0;
@ -1921,7 +1915,7 @@ static ssize_t sysfs_blk_trace_attr_store(struct device *dev,
if (bt == NULL) {
ret = blk_trace_setup_queue(q, bdev);
bt = rcu_dereference_protected(q->blk_trace,
lockdep_is_held(&q->blk_trace_mutex));
lockdep_is_held(&q->debugfs_mutex));
}
if (ret == 0) {
@ -1936,7 +1930,7 @@ static ssize_t sysfs_blk_trace_attr_store(struct device *dev,
}
out_unlock_bdev:
mutex_unlock(&q->blk_trace_mutex);
mutex_unlock(&q->debugfs_mutex);
out_bdput:
bdput(bdev);
out: