btrfs: Add comments on locking of several device-related fields
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Message ID 20190507142428.6531-1-nborisov@suse.com
State New
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  • btrfs: Add comments on locking of several device-related fields
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Commit Message

Nikolay Borisov May 7, 2019, 2:24 p.m. UTC
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
---
 fs/btrfs/volumes.h | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

Comments

David Sterba May 9, 2019, 1:55 p.m. UTC | #1
On Tue, May 07, 2019 at 05:24:28PM +0300, Nikolay Borisov wrote:
> Signed-off-by: Nikolay Borisov <nborisov@suse.com>
> ---
>  fs/btrfs/volumes.h | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
> index 3b97e8092ba7..514799362244 100644
> --- a/fs/btrfs/volumes.h
> +++ b/fs/btrfs/volumes.h
> @@ -52,8 +52,8 @@ struct btrfs_io_geometry {
>  #define BTRFS_DEV_STATE_FLUSH_SENT	(4)
>  
>  struct btrfs_device {
> -	struct list_head dev_list;
> -	struct list_head dev_alloc_list;
> +	struct list_head dev_list; /* device_list_mutex */
> +	struct list_head dev_alloc_list; /* chunk mutex */
>  	struct list_head post_commit_list; /* chunk mutex */

Please update the documentation in the comment 'Device locking' in
volumes.c
Nikolay Borisov May 9, 2019, 2:12 p.m. UTC | #2
On 9.05.19 г. 16:55 ч., David Sterba wrote:
> On Tue, May 07, 2019 at 05:24:28PM +0300, Nikolay Borisov wrote:
>> Signed-off-by: Nikolay Borisov <nborisov@suse.com>
>> ---
>>  fs/btrfs/volumes.h | 11 ++++++++---
>>  1 file changed, 8 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
>> index 3b97e8092ba7..514799362244 100644
>> --- a/fs/btrfs/volumes.h
>> +++ b/fs/btrfs/volumes.h
>> @@ -52,8 +52,8 @@ struct btrfs_io_geometry {
>>  #define BTRFS_DEV_STATE_FLUSH_SENT	(4)
>>  
>>  struct btrfs_device {
>> -	struct list_head dev_list;
>> -	struct list_head dev_alloc_list;
>> +	struct list_head dev_list; /* device_list_mutex */
>> +	struct list_head dev_alloc_list; /* chunk mutex */
>>  	struct list_head post_commit_list; /* chunk mutex */
> 
> Please update the documentation in the comment 'Device locking' in
> volumes.c
> 

Right the only thing that is missing from the Device Locking comment is
the mention of post_commit_list. However, dev_list and dev_alloc_list
are essentially "the other side" of btrfs_fs_devices::alloc_list  hence
I've added them as inline comments. I think it makes more sense to those
small comments next to the variables at least as a remainder.
David Sterba May 9, 2019, 2:31 p.m. UTC | #3
On Thu, May 09, 2019 at 05:12:16PM +0300, Nikolay Borisov wrote:
> 
> 
> On 9.05.19 г. 16:55 ч., David Sterba wrote:
> > On Tue, May 07, 2019 at 05:24:28PM +0300, Nikolay Borisov wrote:
> >> Signed-off-by: Nikolay Borisov <nborisov@suse.com>
> >> ---
> >>  fs/btrfs/volumes.h | 11 ++++++++---
> >>  1 file changed, 8 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
> >> index 3b97e8092ba7..514799362244 100644
> >> --- a/fs/btrfs/volumes.h
> >> +++ b/fs/btrfs/volumes.h
> >> @@ -52,8 +52,8 @@ struct btrfs_io_geometry {
> >>  #define BTRFS_DEV_STATE_FLUSH_SENT	(4)
> >>  
> >>  struct btrfs_device {
> >> -	struct list_head dev_list;
> >> -	struct list_head dev_alloc_list;
> >> +	struct list_head dev_list; /* device_list_mutex */
> >> +	struct list_head dev_alloc_list; /* chunk mutex */
> >>  	struct list_head post_commit_list; /* chunk mutex */
> > 
> > Please update the documentation in the comment 'Device locking' in
> > volumes.c
> 
> Right the only thing that is missing from the Device Locking comment is
> the mention of post_commit_list. However, dev_list and dev_alloc_list
> are essentially "the other side" of btrfs_fs_devices::alloc_list  hence
> I've added them as inline comments. I think it makes more sense to those
> small comments next to the variables at least as a remainder.

Ok.

Patch
diff mbox series

diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 3b97e8092ba7..514799362244 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -52,8 +52,8 @@  struct btrfs_io_geometry {
 #define BTRFS_DEV_STATE_FLUSH_SENT	(4)
 
 struct btrfs_device {
-	struct list_head dev_list;
-	struct list_head dev_alloc_list;
+	struct list_head dev_list; /* device_list_mutex */
+	struct list_head dev_alloc_list; /* chunk mutex */
 	struct list_head post_commit_list; /* chunk mutex */
 	struct btrfs_fs_devices *fs_devices;
 	struct btrfs_fs_info *fs_info;
@@ -238,9 +238,14 @@  struct btrfs_fs_devices {
 	 * this mutex lock.
 	 */
 	struct mutex device_list_mutex;
+
+	/* List of all devices, protected by device_list_mutex */
 	struct list_head devices;
 
-	/* devices not currently being allocated */
+	/*
+	 * Devices which can satisfy space allocation. Protected by
+	 * chunk_mutex
+	 */
 	struct list_head alloc_list;
 
 	struct btrfs_fs_devices *seed;