Message-ID: <20150128081712.GB11548@quack.suse.cz>
Date:	Wed, 28 Jan 2015 09:17:13 +0100
From:	Jan Kara <jack@...e.cz>
To:	Heinrich Schuchardt <xypron.glpk@....de>
Cc:	Zhang Zhen <zhenzhang.zhang@...wei.com>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	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

  Hello,

On Tue 27-01-15 22:52:55, Heinrich Schuchardt wrote:
> 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 superseded by the inotify.7, inotify_init.2, inotify_rm_watch.2, and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?
  I think the 'Rationale' section is still useful and should stay. I'd
remove the rest - just refer to manpages for user interface.

								Honza
> 
> 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?
> > 
> 
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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