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SubjectRe: [PATCH v2] inotify: update documentation to reflect code changes
Hi Andrew Morton,

I noticed there is no a git tree about notify, and i don't know which tree this
patch should be included in.
Can you include this patch in your git tree?

Best regards!
On 2015/2/5 22:49, Jan Kara wrote:
> On Wed 04-02-15 11:01:56, Zhang Zhen wrote:
>> The inotify interface has changed a lot. The user interface was
>> too old, and the kernel interface was removed by Eric Paris in
>> commit: 2dfc1ca inotify: remove inotify in kernel interface.
>>
>> Change v1 -> v2:
>> - Deleted the user interface following Heinrich's and Honza's suggestion
>>
>> Signed-off-by: Zhang Zhen <zhenzhang.zhang@huawei.com>
> You can add:
> Acked-by: Jan Kara <jack@suse.cz>
>
> Honza
>
>> ---
>> Documentation/filesystems/inotify.txt | 197 +---------------------------------
>> 1 file changed, 3 insertions(+), 194 deletions(-)
>>
>> diff --git a/Documentation/filesystems/inotify.txt b/Documentation/filesystems/inotify.txt
>> index cfd0271..51f61db 100644
>> --- a/Documentation/filesystems/inotify.txt
>> +++ b/Documentation/filesystems/inotify.txt
>> @@ -4,201 +4,10 @@
>>
>>
>> Document started 15 Mar 2005 by Robert Love <rml@novell.com>
>> +Document updated 4 Jan 2015 by Zhang Zhen <zhenzhang.zhang@huawei.com>
>> + --Deleted obsoleted interface, just refer to manpages for user interface.
>>
>> -
>> -(i) User Interface
>> -
>> -Inotify is controlled by a set of three system calls and normal file I/O on a
>> -returned file descriptor.
>> -
>> -First step in using inotify is to initialise an inotify instance:
>> -
>> - int fd = inotify_init ();
>> -
>> -Each instance is associated with a unique, ordered queue.
>> -
>> -Change events are managed by "watches". A watch is an (object,mask) pair where
>> -the object is a file or directory and the mask is a bit mask of one or more
>> -inotify events that the application wishes to receive. See <linux/inotify.h>
>> -for valid events. A watch is referenced by a watch descriptor, or wd.
>> -
>> -Watches are added via a path to the file.
>> -
>> -Watches on a directory will return events on any files inside of the directory.
>> -
>> -Adding a watch is simple:
>> -
>> - int wd = inotify_add_watch (fd, path, mask);
>> -
>> -Where "fd" is the return value from inotify_init(), path is the path to the
>> -object to watch, and mask is the watch mask (see <linux/inotify.h>).
>> -
>> -You can update an existing watch in the same manner, by passing in a new mask.
>> -
>> -An existing watch is removed via
>> -
>> - int ret = inotify_rm_watch (fd, wd);
>> -
>> -Events are provided in the form of an inotify_event structure that is read(2)
>> -from a given inotify instance. The filename is of dynamic length and follows
>> -the struct. It is of size len. The filename is padded with null bytes to
>> -ensure proper alignment. This padding is reflected in len.
>> -
>> -You can slurp multiple events by passing a large buffer, for example
>> -
>> - size_t len = read (fd, buf, BUF_LEN);
>> -
>> -Where "buf" is a pointer to an array of "inotify_event" structures at least
>> -BUF_LEN bytes in size. The above example will return as many events as are
>> -available and fit in BUF_LEN.
>> -
>> -Each inotify instance fd is also select()- and poll()-able.
>> -
>> -You can find the size of the current event queue via the standard FIONREAD
>> -ioctl on the fd returned by inotify_init().
>> -
>> -All watches are destroyed and cleaned up on close.
>> -
>> -
>> -(ii)
>> -
>> -Prototypes:
>> -
>> - int inotify_init (void);
>> - int inotify_add_watch (int fd, const char *path, __u32 mask);
>> - 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
>> -
>> -Each inotify instance is represented by an inotify_handle structure.
>> -Inotify's userspace consumers also have an inotify_device which is
>> -associated with the inotify_handle, and on which events are queued.
>> -
>> -Each watch is associated with an inotify_watch structure. Watches are chained
>> -off of each associated inotify_handle and each associated inode.
>> -
>> -See fs/notify/inotify/inotify_fsnotify.c and fs/notify/inotify/inotify_user.c
>> -for the locking and lifetime rules.
>> -
>> -
>> -(vi) Rationale
>> +(i) Rationale
>>
>> Q: What is the design decision behind not tying the watch to the open fd of
>> the watched object?
>> --
>> 1.8.5.5
>>
>>
>> .
>>
>>
>>
>>




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