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-rw-r--r--Documentation/filesystems/nfs/Exporting27
1 files changed, 19 insertions, 8 deletions
diff --git a/Documentation/filesystems/nfs/Exporting b/Documentation/filesystems/nfs/Exporting
index 520a4becb75c..63889149f532 100644
--- a/Documentation/filesystems/nfs/Exporting
+++ b/Documentation/filesystems/nfs/Exporting
@@ -56,13 +56,25 @@ a/ A dentry flag DCACHE_DISCONNECTED which is set on
any dentry that might not be part of the proper prefix.
This is set when anonymous dentries are created, and cleared when a
dentry is noticed to be a child of a dentry which is in the proper
- prefix.
-
-b/ A per-superblock list "s_anon" of dentries which are the roots of
- subtrees that are not in the proper prefix. These dentries, as
- well as the proper prefix, need to be released at unmount time. As
- these dentries will not be hashed, they are linked together on the
- d_hash list_head.
+ prefix. If the refcount on a dentry with this flag set
+ becomes zero, the dentry is immediately discarded, rather than being
+ kept in the dcache. If a dentry that is not already in the dcache
+ is repeatedly accessed by filehandle (as NFSD might do), an new dentry
+ will be a allocated for each access, and discarded at the end of
+ the access.
+
+ Note that such a dentry can acquire children, name, ancestors, etc.
+ without losing DCACHE_DISCONNECTED - that flag is only cleared when
+ subtree is successfully reconnected to root. Until then dentries
+ in such subtree are retained only as long as there are references;
+ refcount reaching zero means immediate eviction, same as for unhashed
+ dentries. That guarantees that we won't need to hunt them down upon
+ umount.
+
+b/ A primitive for creation of secondary roots - d_obtain_root(inode).
+ Those do _not_ bear DCACHE_DISCONNECTED. They are placed on the
+ per-superblock list (->s_roots), so they can be located at umount
+ time for eviction purposes.
c/ Helper routines to allocate anonymous dentries, and to help attach
loose directory dentries at lookup time. They are:
@@ -77,7 +89,6 @@ c/ Helper routines to allocate anonymous dentries, and to help attach
(such as an anonymous one created by d_obtain_alias), if appropriate.
It returns NULL when the passed-in dentry is used, following the calling
convention of ->lookup.
-
Filesystem Issues
-----------------