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authorMiklos Szeredi <mszeredi@suse.cz>2012-06-05 15:10:17 +0200
committerAl Viro <viro@zeniv.linux.org.uk>2012-07-14 16:33:04 +0400
commitd18e9008c377dc6a6d2166a6840bf3a23a5867fd (patch)
tree6bbb29aea7e931b603bd4cea3cc74a0eda7b6379 /fs/open.c
parent54ef487241e863a6046536ac5b1fcd5d7cde86e5 (diff)
vfs: add i_op->atomic_open()
Add a new inode operation which is called on the last component of an open. Using this the filesystem can look up, possibly create and open the file in one atomic operation. If it cannot perform this (e.g. the file type turned out to be wrong) it may signal this by returning NULL instead of an open struct file pointer. i_op->atomic_open() is only called if the last component is negative or needs lookup. Handling cached positive dentries here doesn't add much value: these can be opened using f_op->open(). If the cached file turns out to be invalid, the open can be retried, this time using ->atomic_open() with a fresh dentry. For now leave the old way of using open intents in lookup and revalidate in place. This will be removed once all the users are converted. David Howells noticed that if ->atomic_open() opens the file but does not create it, handle_truncate() will be called on it even if it is not a regular file. Fix this by checking the file type in this case too. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/open.c')
-rw-r--r--fs/open.c42
1 files changed, 42 insertions, 0 deletions
diff --git a/fs/open.c b/fs/open.c
index 1540632d838..13bece4f36a 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -811,6 +811,48 @@ out_err:
EXPORT_SYMBOL_GPL(lookup_instantiate_filp);
/**
+ * finish_open - finish opening a file
+ * @od: opaque open data
+ * @dentry: pointer to dentry
+ * @open: open callback
+ *
+ * This can be used to finish opening a file passed to i_op->atomic_open().
+ *
+ * If the open callback is set to NULL, then the standard f_op->open()
+ * filesystem callback is substituted.
+ */
+struct file *finish_open(struct opendata *od, struct dentry *dentry,
+ int (*open)(struct inode *, struct file *))
+{
+ struct file *res;
+
+ mntget(od->mnt);
+ dget(dentry);
+
+ res = do_dentry_open(dentry, od->mnt, *od->filp, open, current_cred());
+ if (!IS_ERR(res))
+ *od->filp = NULL;
+
+ return res;
+}
+EXPORT_SYMBOL(finish_open);
+
+/**
+ * finish_no_open - finish ->atomic_open() without opening the file
+ *
+ * @od: opaque open data
+ * @dentry: dentry or NULL (as returned from ->lookup())
+ *
+ * This can be used to set the result of a successful lookup in ->atomic_open().
+ * The filesystem's atomic_open() method shall return NULL after calling this.
+ */
+void finish_no_open(struct opendata *od, struct dentry *dentry)
+{
+ od->dentry = dentry;
+}
+EXPORT_SYMBOL(finish_no_open);
+
+/**
* nameidata_to_filp - convert a nameidata to an open filp.
* @nd: pointer to nameidata
* @flags: open flags