path: root/Documentation/filesystems/vfs.txt
diff options
authorNick Piggin <npiggin@kernel.dk>2011-01-07 17:49:23 +1100
committerNick Piggin <npiggin@kernel.dk>2011-01-07 17:50:18 +1100
commitfe15ce446beb3a33583af81ffe6c9d01a75314ed (patch)
treebc8af66b6dd2d0f21a2a3f48a19975ae2cdbae4e /Documentation/filesystems/vfs.txt
parent5eef7fa905c814826f518aca2d414ca77508ce30 (diff)
fs: change d_delete semantics
Change d_delete from a dentry deletion notification to a dentry caching advise, more like ->drop_inode. Require it to be constant and idempotent, and not take d_lock. This is how all existing filesystems use the callback anyway. This makes fine grained dentry locking of dput and dentry lru scanning much simpler. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Diffstat (limited to 'Documentation/filesystems/vfs.txt')
1 files changed, 13 insertions, 14 deletions
diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
index 20899e095e7e..95c0a93f056c 100644
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -847,9 +847,9 @@ defined:
struct dentry_operations {
int (*d_revalidate)(struct dentry *, struct nameidata *);
- int (*d_hash) (struct dentry *, struct qstr *);
- int (*d_compare) (struct dentry *, struct qstr *, struct qstr *);
- int (*d_delete)(struct dentry *);
+ int (*d_hash)(struct dentry *, struct qstr *);
+ int (*d_compare)(struct dentry *, struct qstr *, struct qstr *);
+ int (*d_delete)(const struct dentry *);
void (*d_release)(struct dentry *);
void (*d_iput)(struct dentry *, struct inode *);
char *(*d_dname)(struct dentry *, char *, int);
@@ -864,9 +864,11 @@ struct dentry_operations {
d_compare: called when a dentry should be compared with another
- d_delete: called when the last reference to a dentry is
- deleted. This means no-one is using the dentry, however it is
- still valid and in the dcache
+ d_delete: called when the last reference to a dentry is dropped and the
+ dcache is deciding whether or not to cache it. Return 1 to delete
+ immediately, or 0 to cache the dentry. Default is NULL which means to
+ always cache a reachable dentry. d_delete must be constant and
+ idempotent.
d_release: called when a dentry is really deallocated
@@ -910,14 +912,11 @@ manipulate dentries:
the usage count)
dput: close a handle for a dentry (decrements the usage count). If
- the usage count drops to 0, the "d_delete" method is called
- and the dentry is placed on the unused list if the dentry is
- still in its parents hash list. Putting the dentry on the
- unused list just means that if the system needs some RAM, it
- goes through the unused list of dentries and deallocates them.
- If the dentry has already been unhashed and the usage count
- drops to 0, in this case the dentry is deallocated after the
- "d_delete" method is called
+ the usage count drops to 0, and the dentry is still in its
+ parent's hash, the "d_delete" method is called to check whether
+ it should be cached. If it should not be cached, or if the dentry
+ is not hashed, it is deleted. Otherwise cached dentries are put
+ into an LRU list to be reclaimed on memory shortage.
d_drop: this unhashes a dentry from its parents hash list. A
subsequent call to dput() will deallocate the dentry if its