From 0b6f5d408bb5df3101eb1944b1f301dea50c7e7e Mon Sep 17 00:00:00 2001 From: Nikolay Borisov Date: Thu, 9 May 2019 18:11:11 +0300 Subject: [PATCH] btrfs: Add comments on locking of several device-related fields Signed-off-by: Nikolay Borisov Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/volumes.c | 4 +++- fs/btrfs/volumes.h | 11 ++++++++--- 2 files changed, 11 insertions(+), 4 deletions(-) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 5514ae801f4c..776f5c7ca7c5 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -239,7 +239,9 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info, * chunk_mutex * ----------- * protects chunks, adding or removing during allocation, trim or when a new - * device is added/removed + * device is added/removed. Additionally it also protects post_commit_list of + * individual devices, since they can be added to the transaction's + * post_commit_list only with chunk_mutex held. * * cleaner_mutex * ------------- diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h index 4a7a4d90ded8..fea7b65a712e 100644 --- a/fs/btrfs/volumes.h +++ b/fs/btrfs/volumes.h @@ -43,8 +43,8 @@ struct btrfs_pending_bios { #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; @@ -229,9 +229,14 @@ 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; -- 2.30.2