Message-ID: <54C808B7.3000705@gmx.de>
Date:	Tue, 27 Jan 2015 22:52:55 +0100
From:	Heinrich Schuchardt <xypron.glpk@....de>
To:	Zhang Zhen <zhenzhang.zhang@...wei.com>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
CC:	Wang Nan <wangnan0@...wei.com>, eparis@...isplace.org,
	rlove@...ve.org, john@...nmccutchan.com, Jan Kara <jack@...e.cz>
Subject: Re: [RESEND PATCH] inotify: update documentation to reflect code
 changes


Sections (i) and (ii) of Documentation/filesystems/inotify.txt have been
superseded by the inotify.7, inotify_init.2, inotify_rm_watch.2, and
inotify_add_watch.2 man-pages which are more detailed. In sections (i)
and (ii) the inotify_init1 system call is missing.

Zhang suggests to drop sections (iii) and (iv) as they are obsolete
since 2010.

Shouldn't we drop the whole file?

Best regards

Heinrich Schuchardt

On 27.01.2015 13:45, Zhang Zhen wrote:
> The inotify kernel interface was removed by Eric Paris
> in this commit: 2dfc1ca inotify: remove inotify in
> kernel interface.
> 
> Signed-off-by: Zhang Zhen <zhenzhang.zhang@...wei.com>
> ---
>  Documentation/filesystems/inotify.txt | 120 +---------------------------------
>  1 file changed, 2 insertions(+), 118 deletions(-)
> 
> diff --git a/Documentation/filesystems/inotify.txt b/Documentation/filesystems/inotify.txt
> index cfd0271..9b74b45 100644
> --- a/Documentation/filesystems/inotify.txt
> +++ b/Documentation/filesystems/inotify.txt
> @@ -69,123 +69,7 @@ Prototypes:
>  	int inotify_rm_watch (int fd, __u32 mask);
> 
> 
> -(iii) Kernel Interface
> -
> -Inotify's kernel API consists a set of functions for managing watches and an
> -event callback.
> -
> -To use the kernel API, you must first initialize an inotify instance with a set
> -of inotify_operations.  You are given an opaque inotify_handle, which you use
> -for any further calls to inotify.
> -
> -    struct inotify_handle *ih = inotify_init(my_event_handler);
> -
> -You must provide a function for processing events and a function for destroying
> -the inotify watch.
> -
> -    void handle_event(struct inotify_watch *watch, u32 wd, u32 mask,
> -    	              u32 cookie, const char *name, struct inode *inode)
> -
> -	watch - the pointer to the inotify_watch that triggered this call
> -	wd - the watch descriptor
> -	mask - describes the event that occurred
> -	cookie - an identifier for synchronizing events
> -	name - the dentry name for affected files in a directory-based event
> -	inode - the affected inode in a directory-based event
> -
> -    void destroy_watch(struct inotify_watch *watch)
> -
> -You may add watches by providing a pre-allocated and initialized inotify_watch
> -structure and specifying the inode to watch along with an inotify event mask.
> -You must pin the inode during the call.  You will likely wish to embed the
> -inotify_watch structure in a structure of your own which contains other
> -information about the watch.  Once you add an inotify watch, it is immediately
> -subject to removal depending on filesystem events.  You must grab a reference if
> -you depend on the watch hanging around after the call.
> -
> -    inotify_init_watch(&my_watch->iwatch);
> -    inotify_get_watch(&my_watch->iwatch);	// optional
> -    s32 wd = inotify_add_watch(ih, &my_watch->iwatch, inode, mask);
> -    inotify_put_watch(&my_watch->iwatch);	// optional
> -
> -You may use the watch descriptor (wd) or the address of the inotify_watch for
> -other inotify operations.  You must not directly read or manipulate data in the
> -inotify_watch.  Additionally, you must not call inotify_add_watch() more than
> -once for a given inotify_watch structure, unless you have first called either
> -inotify_rm_watch() or inotify_rm_wd().
> -
> -To determine if you have already registered a watch for a given inode, you may
> -call inotify_find_watch(), which gives you both the wd and the watch pointer for
> -the inotify_watch, or an error if the watch does not exist.
> -
> -    wd = inotify_find_watch(ih, inode, &watchp);
> -
> -You may use container_of() on the watch pointer to access your own data
> -associated with a given watch.  When an existing watch is found,
> -inotify_find_watch() bumps the refcount before releasing its locks.  You must
> -put that reference with:
> -
> -    put_inotify_watch(watchp);
> -
> -Call inotify_find_update_watch() to update the event mask for an existing watch.
> -inotify_find_update_watch() returns the wd of the updated watch, or an error if
> -the watch does not exist.
> -
> -    wd = inotify_find_update_watch(ih, inode, mask);
> -
> -An existing watch may be removed by calling either inotify_rm_watch() or
> -inotify_rm_wd().
> -
> -    int ret = inotify_rm_watch(ih, &my_watch->iwatch);
> -    int ret = inotify_rm_wd(ih, wd);
> -
> -A watch may be removed while executing your event handler with the following:
> -
> -    inotify_remove_watch_locked(ih, iwatch);
> -
> -Call inotify_destroy() to remove all watches from your inotify instance and
> -release it.  If there are no outstanding references, inotify_destroy() will call
> -your destroy_watch op for each watch.
> -
> -    inotify_destroy(ih);
> -
> -When inotify removes a watch, it sends an IN_IGNORED event to your callback.
> -You may use this event as an indication to free the watch memory.  Note that
> -inotify may remove a watch due to filesystem events, as well as by your request.
> -If you use IN_ONESHOT, inotify will remove the watch after the first event, at
> -which point you may call the final inotify_put_watch.
> -
> -(iv) Kernel Interface Prototypes
> -
> -	struct inotify_handle *inotify_init(struct inotify_operations *ops);
> -
> -	inotify_init_watch(struct inotify_watch *watch);
> -
> -	s32 inotify_add_watch(struct inotify_handle *ih,
> -		              struct inotify_watch *watch,
> -			      struct inode *inode, u32 mask);
> -
> -	s32 inotify_find_watch(struct inotify_handle *ih, struct inode *inode,
> -			       struct inotify_watch **watchp);
> -
> -	s32 inotify_find_update_watch(struct inotify_handle *ih,
> -				      struct inode *inode, u32 mask);
> -
> -	int inotify_rm_wd(struct inotify_handle *ih, u32 wd);
> -
> -	int inotify_rm_watch(struct inotify_handle *ih,
> -			     struct inotify_watch *watch);
> -
> -	void inotify_remove_watch_locked(struct inotify_handle *ih,
> -					 struct inotify_watch *watch);
> -
> -	void inotify_destroy(struct inotify_handle *ih);
> -
> -	void get_inotify_watch(struct inotify_watch *watch);
> -	void put_inotify_watch(struct inotify_watch *watch);
> -
> -
> -(v) Internal Kernel Implementation
> +(iii) Internal Kernel Implementation
> 
>  Each inotify instance is represented by an inotify_handle structure.
>  Inotify's userspace consumers also have an inotify_device which is
> @@ -198,7 +82,7 @@ See fs/notify/inotify/inotify_fsnotify.c and fs/notify/inotify/inotify_user.c
>  for the locking and lifetime rules.
> 
> 
> -(vi) Rationale
> +(iv) Rationale
> 
>  Q: What is the design decision behind not tying the watch to the open fd of
>     the watched object?
> 

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