diff mbox series

[04/11] btrfs: reada: use sprout device_list_mutex

Message ID b5ad15e6583f4e61cfd44344ef17ea7a93f6bb57.1598792561.git.anand.jain@oracle.com
State New, archived
Headers show
Series btrfs: seed fix null ptr, use only main device_list_mutex, and cleanups | expand

Commit Message

Anand Jain Aug. 30, 2020, 2:40 p.m. UTC
On an fs mounted using a sprout-device, the seed fs_devices are maintained
in a linked list under fs_info->fs_devices. Each seed's fs_devices also
have device_list_mutex initialized to protect against the potential race
with delete threads. But the delete thread (at btrfs_rm_device()) is holding
the fs_info::fs_devices::device_list_mutex mutex which is sprout's
device_list_mutex instead of seed's device_list_mutex. Moreover, there
aren't any significient benefits in using the seed::device_list_mutex
instead of sprout::device_list_mutex.

So this patch converts them of using the seed::device_list_mutex to
sprout::device_list_mutex.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
 fs/btrfs/reada.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

Comments

Nikolay Borisov Aug. 31, 2020, 8:54 a.m. UTC | #1
On 30.08.20 г. 17:40 ч., Anand Jain wrote:
> On an fs mounted using a sprout-device, the seed fs_devices are maintained
> in a linked list under fs_info->fs_devices. Each seed's fs_devices also
> have device_list_mutex initialized to protect against the potential race
> with delete threads. But the delete thread (at btrfs_rm_device()) is holding
> the fs_info::fs_devices::device_list_mutex mutex which is sprout's
> device_list_mutex instead of seed's device_list_mutex. Moreover, there
> aren't any significient benefits in using the seed::device_list_mutex
> instead of sprout::device_list_mutex.
> 
> So this patch converts them of using the seed::device_list_mutex to
> sprout::device_list_mutex.
> 
> Signed-off-by: Anand Jain <anand.jain@oracle.com>

nit: I'm beginning to think that the structure representing seed devices
shouldn't be a full-fledged btrfs_fs_devices but a slimmed down version
which contains only the necessary bits.


Reviewed-by: Nikolay Borisov <nborisov@suse.com>

> ---
>  fs/btrfs/reada.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/btrfs/reada.c b/fs/btrfs/reada.c
> index c0035fc0ec67..9b54a51ba860 100644
> --- a/fs/btrfs/reada.c
> +++ b/fs/btrfs/reada.c
> @@ -776,13 +776,11 @@ static int __reada_start_for_fsdevs(struct btrfs_fs_devices *fs_devices)
>  
>  	do {
>  		enqueued = 0;
> -		mutex_lock(&fs_devices->device_list_mutex);
>  		list_for_each_entry(device, &fs_devices->devices, dev_list) {
>  			if (atomic_read(&device->reada_in_flight) <
>  			    MAX_IN_FLIGHT)
>  				enqueued += reada_start_machine_dev(device);
>  		}
> -		mutex_unlock(&fs_devices->device_list_mutex);
>  		total += enqueued;
>  	} while (enqueued && total < 10000);
>  
> @@ -795,10 +793,13 @@ static void __reada_start_machine(struct btrfs_fs_info *fs_info)
>  	int i;
>  	u64 enqueued = 0;
>  
> +	mutex_lock(&fs_devices->device_list_mutex);
> +
>  	enqueued += __reada_start_for_fsdevs(fs_devices);
>  	list_for_each_entry(seed_devs, &fs_devices->seed_list, seed_list)
>  		enqueued += __reada_start_for_fsdevs(seed_devs);
>  
> +	mutex_unlock(&fs_devices->device_list_mutex);
>  	if (enqueued == 0)
>  		return;
>  
>
Josef Bacik Aug. 31, 2020, 4:08 p.m. UTC | #2
On 8/30/20 10:40 AM, Anand Jain wrote:
> On an fs mounted using a sprout-device, the seed fs_devices are maintained
> in a linked list under fs_info->fs_devices. Each seed's fs_devices also
> have device_list_mutex initialized to protect against the potential race
> with delete threads. But the delete thread (at btrfs_rm_device()) is holding
> the fs_info::fs_devices::device_list_mutex mutex which is sprout's
> device_list_mutex instead of seed's device_list_mutex. Moreover, there
> aren't any significient benefits in using the seed::device_list_mutex
> instead of sprout::device_list_mutex.
> 
> So this patch converts them of using the seed::device_list_mutex to
> sprout::device_list_mutex.
> 
> Signed-off-by: Anand Jain <anand.jain@oracle.com>

This doesn't apply cleanly to misc-next as of this morning.  Thanks,

Josef
Anand Jain Sept. 1, 2020, 9:02 a.m. UTC | #3
On 1/9/20 12:08 am, Josef Bacik wrote:
> On 8/30/20 10:40 AM, Anand Jain wrote:
>> On an fs mounted using a sprout-device, the seed fs_devices are 
>> maintained
>> in a linked list under fs_info->fs_devices. Each seed's fs_devices also
>> have device_list_mutex initialized to protect against the potential race
>> with delete threads. But the delete thread (at btrfs_rm_device()) is 
>> holding
>> the fs_info::fs_devices::device_list_mutex mutex which is sprout's
>> device_list_mutex instead of seed's device_list_mutex. Moreover, there
>> aren't any significient benefits in using the seed::device_list_mutex
>> instead of sprout::device_list_mutex.
>>
>> So this patch converts them of using the seed::device_list_mutex to
>> sprout::device_list_mutex.
>>
>> Signed-off-by: Anand Jain <anand.jain@oracle.com>
> 
> This doesn't apply cleanly to misc-next as of this morning.  Thanks,

   Kdave renamed the function to reada_start_for_fsdevs() dropping
   the __ prefix. Rebased my misc-next. I am sending V2.

Thanks, Anand

> 
> Josef
diff mbox series

Patch

diff --git a/fs/btrfs/reada.c b/fs/btrfs/reada.c
index c0035fc0ec67..9b54a51ba860 100644
--- a/fs/btrfs/reada.c
+++ b/fs/btrfs/reada.c
@@ -776,13 +776,11 @@  static int __reada_start_for_fsdevs(struct btrfs_fs_devices *fs_devices)
 
 	do {
 		enqueued = 0;
-		mutex_lock(&fs_devices->device_list_mutex);
 		list_for_each_entry(device, &fs_devices->devices, dev_list) {
 			if (atomic_read(&device->reada_in_flight) <
 			    MAX_IN_FLIGHT)
 				enqueued += reada_start_machine_dev(device);
 		}
-		mutex_unlock(&fs_devices->device_list_mutex);
 		total += enqueued;
 	} while (enqueued && total < 10000);
 
@@ -795,10 +793,13 @@  static void __reada_start_machine(struct btrfs_fs_info *fs_info)
 	int i;
 	u64 enqueued = 0;
 
+	mutex_lock(&fs_devices->device_list_mutex);
+
 	enqueued += __reada_start_for_fsdevs(fs_devices);
 	list_for_each_entry(seed_devs, &fs_devices->seed_list, seed_list)
 		enqueued += __reada_start_for_fsdevs(seed_devs);
 
+	mutex_unlock(&fs_devices->device_list_mutex);
 	if (enqueued == 0)
 		return;