diff options
Diffstat (limited to 'Documentation/filesystems')
| -rw-r--r-- | Documentation/filesystems/Locking | 4 | ||||
| -rw-r--r-- | Documentation/filesystems/porting | 7 | ||||
| -rw-r--r-- | Documentation/filesystems/vfs.txt | 26 |
3 files changed, 33 insertions, 4 deletions
diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking index 33fa3e5d38fd..9a76f8d8bf95 100644 --- a/Documentation/filesystems/Locking +++ b/Documentation/filesystems/Locking @@ -11,7 +11,9 @@ be able to use diff(1). prototypes: int (*d_revalidate)(struct dentry *, int); int (*d_hash) (struct dentry *, struct qstr *); - int (*d_compare) (struct dentry *, struct qstr *, struct qstr *); + int (*d_compare)(const struct dentry *, const struct inode *, + const struct dentry *, const struct inode *, + unsigned int, const char *, const struct qstr *); int (*d_delete)(struct dentry *); void (*d_release)(struct dentry *); void (*d_iput)(struct dentry *, struct inode *); diff --git a/Documentation/filesystems/porting b/Documentation/filesystems/porting index 9e71c9ad3108..d44511e20828 100644 --- a/Documentation/filesystems/porting +++ b/Documentation/filesystems/porting @@ -326,3 +326,10 @@ to it. unreferenced dentries, and is now only called when the dentry refcount goes to 0. Even on 0 refcount transition, it must be able to tolerate being called 0, 1, or more times (eg. constant, idempotent). + +--- +[mandatory] + + .d_compare() calling convention and locking rules are significantly +changed. Read updated documentation in Documentation/filesystems/vfs.txt (and +look at examples of other filesystems) for guidance. diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt index 95c0a93f056c..250681b8c7cc 100644 --- a/Documentation/filesystems/vfs.txt +++ b/Documentation/filesystems/vfs.txt @@ -848,7 +848,9 @@ 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_compare)(const struct dentry *, const struct inode *, + const struct dentry *, const struct inode *, + unsigned int, const char *, const struct qstr *); int (*d_delete)(const struct dentry *); void (*d_release)(struct dentry *); void (*d_iput)(struct dentry *, struct inode *); @@ -860,9 +862,27 @@ struct dentry_operations { dcache. Most filesystems leave this as NULL, because all their dentries in the dcache are valid - d_hash: called when the VFS adds a dentry to the hash table + d_hash: called when the VFS adds a dentry to the hash table. The first + dentry passed to d_hash is the parent directory that the name is + to be hashed into. - d_compare: called when a dentry should be compared with another + d_compare: called to compare a dentry name with a given name. The first + dentry is the parent of the dentry to be compared, the second is + the parent's inode, then the dentry and inode (may be NULL) of the + child dentry. len and name string are properties of the dentry to be + compared. qstr is the name to compare it with. + + Must be constant and idempotent, and should not take locks if + possible, and should not or store into the dentry or inodes. + Should not dereference pointers outside the dentry or inodes without + lots of care (eg. d_parent, d_inode, d_name should not be used). + + However, our vfsmount is pinned, and RCU held, so the dentries and + inodes won't disappear, neither will our sb or filesystem module. + ->i_sb and ->d_sb may be used. + + It is a tricky calling convention because it needs to be called under + "rcu-walk", ie. without any locks or references on things. 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 |