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Message-ID: <54D41C37.2090504@huawei.com> Date: Fri, 6 Feb 2015 09:43:19 +0800 From: Zhang Zhen <zhenzhang.zhang@...wei.com> To: Jan Kara <jack@...e.cz> CC: <linux-fsdevel@...r.kernel.org>, <linux-kernel@...r.kernel.org>, <eparis@...isplace.org>, <robert.w.love@...el.com>, <john@...nmccutchan.com>, Heinrich Schuchardt <xypron.glpk@....de>, Andrew Morton <akpm@...ux-foundation.org> Subject: Re: [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@...wei.com> > You can add: > Acked-by: Jan Kara <jack@...e.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@...ell.com> >> +Document updated 4 Jan 2015 by Zhang Zhen <zhenzhang.zhang@...wei.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 >> >> >> . >> >> >> >> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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