VFS: Allow the filesystem to return a full file pointer on open intent
This is needed by NFSv4 for atomicity reasons: our open command is in
fact a lookup+open, so we need to be able to propagate open context
information from lookup() into the resulting struct file's
private_data field.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/open.c b/fs/open.c
index f0d90cf..8d06ec9 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -739,7 +739,8 @@
}
static struct file *__dentry_open(struct dentry *dentry, struct vfsmount *mnt,
- int flags, struct file *f)
+ int flags, struct file *f,
+ int (*open)(struct inode *, struct file *))
{
struct inode *inode;
int error;
@@ -761,11 +762,14 @@
f->f_op = fops_get(inode->i_fop);
file_move(f, &inode->i_sb->s_files);
- if (f->f_op && f->f_op->open) {
- error = f->f_op->open(inode,f);
+ if (!open && f->f_op)
+ open = f->f_op->open;
+ if (open) {
+ error = open(inode, f);
if (error)
goto cleanup_all;
}
+
f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);
@@ -814,28 +818,75 @@
{
int namei_flags, error;
struct nameidata nd;
- struct file *f;
namei_flags = flags;
if ((namei_flags+1) & O_ACCMODE)
namei_flags++;
- if (namei_flags & O_TRUNC)
- namei_flags |= 2;
-
- error = -ENFILE;
- f = get_empty_filp();
- if (f == NULL)
- return ERR_PTR(error);
error = open_namei(filename, namei_flags, mode, &nd);
if (!error)
- return __dentry_open(nd.dentry, nd.mnt, flags, f);
+ return nameidata_to_filp(&nd, flags);
- put_filp(f);
return ERR_PTR(error);
}
EXPORT_SYMBOL(filp_open);
+/**
+ * lookup_instantiate_filp - instantiates the open intent filp
+ * @nd: pointer to nameidata
+ * @dentry: pointer to dentry
+ * @open: open callback
+ *
+ * Helper for filesystems that want to use lookup open intents and pass back
+ * a fully instantiated struct file to the caller.
+ * This function is meant to be called from within a filesystem's
+ * lookup method.
+ * Note that in case of error, nd->intent.open.file is destroyed, but the
+ * path information remains valid.
+ * If the open callback is set to NULL, then the standard f_op->open()
+ * filesystem callback is substituted.
+ */
+struct file *lookup_instantiate_filp(struct nameidata *nd, struct dentry *dentry,
+ int (*open)(struct inode *, struct file *))
+{
+ if (IS_ERR(nd->intent.open.file))
+ goto out;
+ if (IS_ERR(dentry))
+ goto out_err;
+ nd->intent.open.file = __dentry_open(dget(dentry), mntget(nd->mnt),
+ nd->intent.open.flags - 1,
+ nd->intent.open.file,
+ open);
+out:
+ return nd->intent.open.file;
+out_err:
+ release_open_intent(nd);
+ nd->intent.open.file = (struct file *)dentry;
+ goto out;
+}
+EXPORT_SYMBOL_GPL(lookup_instantiate_filp);
+
+/**
+ * nameidata_to_filp - convert a nameidata to an open filp.
+ * @nd: pointer to nameidata
+ * @flags: open flags
+ *
+ * Note that this function destroys the original nameidata
+ */
+struct file *nameidata_to_filp(struct nameidata *nd, int flags)
+{
+ struct file *filp;
+
+ /* Pick up the filp from the open intent */
+ filp = nd->intent.open.file;
+ /* Has the filesystem initialised the file for us? */
+ if (filp->f_dentry == NULL)
+ filp = __dentry_open(nd->dentry, nd->mnt, flags, filp, NULL);
+ else
+ path_release(nd);
+ return filp;
+}
+
struct file *dentry_open(struct dentry *dentry, struct vfsmount *mnt, int flags)
{
int error;
@@ -846,7 +897,7 @@
if (f == NULL)
return ERR_PTR(error);
- return __dentry_open(dentry, mnt, flags, f);
+ return __dentry_open(dentry, mnt, flags, f, NULL);
}
EXPORT_SYMBOL(dentry_open);