* [PATCH v2 (RESEND)] brd: reduce the brd_devices_mutex scope
@ 2021-10-02 9:19 Tetsuo Handa
2021-10-02 13:28 ` Jens Axboe
0 siblings, 1 reply; 2+ messages in thread
From: Tetsuo Handa @ 2021-10-02 9:19 UTC (permalink / raw)
To: Jens Axboe; +Cc: linux-block, Christoph Hellwig
As with commit 8b52d8be86d72308 ("loop: reorder loop_exit"),
unregister_blkdev() needs to be called first in order to avoid calling
brd_alloc() from brd_probe() after brd_del_one() from brd_exit(). Then,
we can avoid holding global mutex during add_disk()/del_gendisk() as with
commit 1c500ad706383f1a ("loop: reduce the loop_ctl_mutex scope").
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
Changes in v2:
s/brd->brd_number != i/brd->brd_number == i/
drivers/block/brd.c | 44 ++++++++++++++++++++++----------------------
1 file changed, 22 insertions(+), 22 deletions(-)
diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index 58ec167aa018..530b31240203 100644
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -373,10 +373,22 @@ static int brd_alloc(int i)
struct gendisk *disk;
char buf[DISK_NAME_LEN];
+ mutex_lock(&brd_devices_mutex);
+ list_for_each_entry(brd, &brd_devices, brd_list) {
+ if (brd->brd_number == i) {
+ mutex_unlock(&brd_devices_mutex);
+ return -EEXIST;
+ }
+ }
brd = kzalloc(sizeof(*brd), GFP_KERNEL);
- if (!brd)
+ if (!brd) {
+ mutex_unlock(&brd_devices_mutex);
return -ENOMEM;
+ }
brd->brd_number = i;
+ list_add_tail(&brd->brd_list, &brd_devices);
+ mutex_unlock(&brd_devices_mutex);
+
spin_lock_init(&brd->brd_lock);
INIT_RADIX_TREE(&brd->brd_pages, GFP_ATOMIC);
@@ -411,37 +423,30 @@ static int brd_alloc(int i)
blk_queue_flag_set(QUEUE_FLAG_NONROT, disk->queue);
blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, disk->queue);
add_disk(disk);
- list_add_tail(&brd->brd_list, &brd_devices);
return 0;
out_free_dev:
+ mutex_lock(&brd_devices_mutex);
+ list_del(&brd->brd_list);
+ mutex_unlock(&brd_devices_mutex);
kfree(brd);
return -ENOMEM;
}
static void brd_probe(dev_t dev)
{
- int i = MINOR(dev) / max_part;
- struct brd_device *brd;
-
- mutex_lock(&brd_devices_mutex);
- list_for_each_entry(brd, &brd_devices, brd_list) {
- if (brd->brd_number == i)
- goto out_unlock;
- }
-
- brd_alloc(i);
-out_unlock:
- mutex_unlock(&brd_devices_mutex);
+ brd_alloc(MINOR(dev) / max_part);
}
static void brd_del_one(struct brd_device *brd)
{
- list_del(&brd->brd_list);
del_gendisk(brd->brd_disk);
blk_cleanup_disk(brd->brd_disk);
brd_free_pages(brd);
+ mutex_lock(&brd_devices_mutex);
+ list_del(&brd->brd_list);
+ mutex_unlock(&brd_devices_mutex);
kfree(brd);
}
@@ -491,25 +496,21 @@ static int __init brd_init(void)
brd_debugfs_dir = debugfs_create_dir("ramdisk_pages", NULL);
- mutex_lock(&brd_devices_mutex);
for (i = 0; i < rd_nr; i++) {
err = brd_alloc(i);
if (err)
goto out_free;
}
- mutex_unlock(&brd_devices_mutex);
-
pr_info("brd: module loaded\n");
return 0;
out_free:
+ unregister_blkdev(RAMDISK_MAJOR, "ramdisk");
debugfs_remove_recursive(brd_debugfs_dir);
list_for_each_entry_safe(brd, next, &brd_devices, brd_list)
brd_del_one(brd);
- mutex_unlock(&brd_devices_mutex);
- unregister_blkdev(RAMDISK_MAJOR, "ramdisk");
pr_info("brd: module NOT loaded !!!\n");
return err;
@@ -519,13 +520,12 @@ static void __exit brd_exit(void)
{
struct brd_device *brd, *next;
+ unregister_blkdev(RAMDISK_MAJOR, "ramdisk");
debugfs_remove_recursive(brd_debugfs_dir);
list_for_each_entry_safe(brd, next, &brd_devices, brd_list)
brd_del_one(brd);
- unregister_blkdev(RAMDISK_MAJOR, "ramdisk");
-
pr_info("brd: module unloaded\n");
}
--
2.30.2
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH v2 (RESEND)] brd: reduce the brd_devices_mutex scope
2021-10-02 9:19 [PATCH v2 (RESEND)] brd: reduce the brd_devices_mutex scope Tetsuo Handa
@ 2021-10-02 13:28 ` Jens Axboe
0 siblings, 0 replies; 2+ messages in thread
From: Jens Axboe @ 2021-10-02 13:28 UTC (permalink / raw)
To: Tetsuo Handa; +Cc: linux-block, Christoph Hellwig
On 10/2/21 3:19 AM, Tetsuo Handa wrote:
> As with commit 8b52d8be86d72308 ("loop: reorder loop_exit"),
> unregister_blkdev() needs to be called first in order to avoid calling
> brd_alloc() from brd_probe() after brd_del_one() from brd_exit(). Then,
> we can avoid holding global mutex during add_disk()/del_gendisk() as with
> commit 1c500ad706383f1a ("loop: reduce the loop_ctl_mutex scope").
Applied for 5.16, thanks.
--
Jens Axboe
^ permalink raw reply [flat|nested] 2+ messages in thread
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2021-10-02 13:28 ` Jens Axboe
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