Message-Id: <201501270812.47160.gheskett@wdtv.com>
Date:	Tue, 27 Jan 2015 08:12:47 -0500
From:	Gene Heskett <gheskett@...v.com>
To:	linux-kernel@...r.kernel.org
Subject: Re: [RESEND PATCH] inotify: update documentation to reflect code changes

On Tuesday 27 January 2015, 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.

As a heavy user of the inotify kit of utils, inotify_wait in particular, I 
object if this removal breaks those tools.

Cheers, Gene Heskett
-- 
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