From 0854d450e229e37102a76e3ccf065d8e8137846f Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Mon, 16 Sep 2013 14:51:55 +0200 Subject: vfs: improve i_op->atomic_open() documentation Fix documentation of ->atomic_open() and related functions: finish_open() and finish_no_open(). Also add details that seem to be unclear and a source of bugs (some of which are fixed in the following series). Cc-ing maintainers of all filesystems implementing ->atomic_open(). Signed-off-by: Miklos Szeredi Cc: Eric Van Hensbergen Cc: Sage Weil Cc: Steve French Cc: Steven Whitehouse Cc: Trond Myklebust Signed-off-by: Al Viro --- fs/open.c | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-) (limited to 'fs/open.c') diff --git a/fs/open.c b/fs/open.c index 2a731b0d08bc..d420331ca32a 100644 --- a/fs/open.c +++ b/fs/open.c @@ -744,14 +744,24 @@ cleanup_file: /** * finish_open - finish opening a file - * @od: opaque open data + * @file: file pointer * @dentry: pointer to dentry * @open: open callback + * @opened: state of open * * 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. + * + * NB: the dentry reference is _not_ consumed. If, for example, the dentry is + * the return value of d_splice_alias(), then the caller needs to perform dput() + * on it after finish_open(). + * + * On successful return @file is a fully instantiated open file. After this, if + * an error occurs in ->atomic_open(), it needs to clean up with fput(). + * + * Returns zero on success or -errno if the open failed. */ int finish_open(struct file *file, struct dentry *dentry, int (*open)(struct inode *, struct file *), @@ -772,11 +782,16 @@ EXPORT_SYMBOL(finish_open); /** * finish_no_open - finish ->atomic_open() without opening the file * - * @od: opaque open data + * @file: file pointer * @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. + * + * NB: unlike finish_open() this function does consume the dentry reference and + * the caller need not dput() it. + * + * Returns "1" which must be the return value of ->atomic_open() after having + * called this function. */ int finish_no_open(struct file *file, struct dentry *dentry) { -- cgit v1.2.3