diff options
-rw-r--r-- | Documentation/filesystems/sharedsubtree.txt | 16 |
1 files changed, 15 insertions, 1 deletions
diff --git a/Documentation/filesystems/sharedsubtree.txt b/Documentation/filesystems/sharedsubtree.txt index 23a181074f94..fc0e39af43c3 100644 --- a/Documentation/filesystems/sharedsubtree.txt +++ b/Documentation/filesystems/sharedsubtree.txt | |||
@@ -837,6 +837,9 @@ replicas continue to be exactly same. | |||
837 | individual lists does not affect propagation or the way propagation | 837 | individual lists does not affect propagation or the way propagation |
838 | tree is modified by operations. | 838 | tree is modified by operations. |
839 | 839 | ||
840 | All vfsmounts in a peer group have the same ->mnt_master. If it is | ||
841 | non-NULL, they form a contiguous (ordered) segment of slave list. | ||
842 | |||
840 | A example propagation tree looks as shown in the figure below. | 843 | A example propagation tree looks as shown in the figure below. |
841 | [ NOTE: Though it looks like a forest, if we consider all the shared | 844 | [ NOTE: Though it looks like a forest, if we consider all the shared |
842 | mounts as a conceptual entity called 'pnode', it becomes a tree] | 845 | mounts as a conceptual entity called 'pnode', it becomes a tree] |
@@ -874,8 +877,19 @@ replicas continue to be exactly same. | |||
874 | 877 | ||
875 | NOTE: The propagation tree is orthogonal to the mount tree. | 878 | NOTE: The propagation tree is orthogonal to the mount tree. |
876 | 879 | ||
880 | 8B Locking: | ||
881 | |||
882 | ->mnt_share, ->mnt_slave, ->mnt_slave_list, ->mnt_master are protected | ||
883 | by namespace_sem (exclusive for modifications, shared for reading). | ||
884 | |||
885 | Normally we have ->mnt_flags modifications serialized by vfsmount_lock. | ||
886 | There are two exceptions: do_add_mount() and clone_mnt(). | ||
887 | The former modifies a vfsmount that has not been visible in any shared | ||
888 | data structures yet. | ||
889 | The latter holds namespace_sem and the only references to vfsmount | ||
890 | are in lists that can't be traversed without namespace_sem. | ||
877 | 891 | ||
878 | 8B Algorithm: | 892 | 8C Algorithm: |
879 | 893 | ||
880 | The crux of the implementation resides in rbind/move operation. | 894 | The crux of the implementation resides in rbind/move operation. |
881 | 895 | ||