diff options
Diffstat (limited to 'Documentation/filesystems/sharedsubtree.txt')
| -rw-r--r-- | Documentation/filesystems/sharedsubtree.txt | 22 |
1 files changed, 18 insertions, 4 deletions
diff --git a/Documentation/filesystems/sharedsubtree.txt b/Documentation/filesystems/sharedsubtree.txt index 23a181074f9..32a173dd315 100644 --- a/Documentation/filesystems/sharedsubtree.txt +++ b/Documentation/filesystems/sharedsubtree.txt @@ -62,10 +62,10 @@ replicas continue to be exactly same. # mount /dev/sd0 /tmp/a #ls /tmp/a - t1 t2 t2 + t1 t2 t3 #ls /mnt/a - t1 t2 t2 + t1 t2 t3 Note that the mount has propagated to the mount at /mnt as well. @@ -727,7 +727,7 @@ replicas continue to be exactly same. mkdir -p /tmp/m3 mount --rbind /root /tmp/m3 - I wont' draw the tree..but it has 24 vfsmounts + I won't draw the tree..but it has 24 vfsmounts at step i the number of vfsmounts is V[i] = i*V[i-1]. @@ -837,6 +837,9 @@ replicas continue to be exactly same. individual lists does not affect propagation or the way propagation tree is modified by operations. + All vfsmounts in a peer group have the same ->mnt_master. If it is + non-NULL, they form a contiguous (ordered) segment of slave list. + A example propagation tree looks as shown in the figure below. [ NOTE: Though it looks like a forest, if we consider all the shared mounts as a conceptual entity called 'pnode', it becomes a tree] @@ -874,8 +877,19 @@ replicas continue to be exactly same. NOTE: The propagation tree is orthogonal to the mount tree. +8B Locking: + + ->mnt_share, ->mnt_slave, ->mnt_slave_list, ->mnt_master are protected + by namespace_sem (exclusive for modifications, shared for reading). + + Normally we have ->mnt_flags modifications serialized by vfsmount_lock. + There are two exceptions: do_add_mount() and clone_mnt(). + The former modifies a vfsmount that has not been visible in any shared + data structures yet. + The latter holds namespace_sem and the only references to vfsmount + are in lists that can't be traversed without namespace_sem. -8B Algorithm: +8C Algorithm: The crux of the implementation resides in rbind/move operation. |