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@xxxxxxxxxx> You can add: Acked-by: Jan Kara <jack@xxxxxxx> 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@xxxxxxxxxx> > +Document updated 4 Jan 2015 by Zhang Zhen <zhenzhang.zhang@xxxxxxxxxx> > + --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 > > > . > > > > -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
