diff options
author | Linus Torvalds <torvalds@g5.osdl.org> | 2006-06-20 15:37:56 -0700 |
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committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-06-20 15:37:56 -0700 |
commit | d9eaec9e295a84a80b663996d0489fcff3a1dca9 (patch) | |
tree | 85cfc09bb5f0eb42d3be7dfbddaad31353307796 /Documentation | |
parent | cee4cca740d209bcb4b9857baa2253d5ba4e3fbe (diff) | |
parent | 41757106b9ca7867dafb2404d618f947b4786fd7 (diff) |
Merge branch 'audit.b21' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/audit-current
* 'audit.b21' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/audit-current: (25 commits)
[PATCH] make set_loginuid obey audit_enabled
[PATCH] log more info for directory entry change events
[PATCH] fix AUDIT_FILTER_PREPEND handling
[PATCH] validate rule fields' types
[PATCH] audit: path-based rules
[PATCH] Audit of POSIX Message Queue Syscalls v.2
[PATCH] fix se_sen audit filter
[PATCH] deprecate AUDIT_POSSBILE
[PATCH] inline more audit helpers
[PATCH] proc_loginuid_write() uses simple_strtoul() on non-terminated array
[PATCH] update of IPC audit record cleanup
[PATCH] minor audit updates
[PATCH] fix audit_krule_to_{rule,data} return values
[PATCH] add filtering by ppid
[PATCH] log ppid
[PATCH] collect sid of those who send signals to auditd
[PATCH] execve argument logging
[PATCH] fix deadlocks in AUDIT_LIST/AUDIT_LIST_RULES
[PATCH] audit_panic() is audit-internal
[PATCH] inotify (5/5): update kernel documentation
...
Manual fixup of conflict in unclude/linux/inotify.h
Diffstat (limited to 'Documentation')
-rw-r--r-- | Documentation/filesystems/inotify.txt | 130 |
1 files changed, 124 insertions, 6 deletions
diff --git a/Documentation/filesystems/inotify.txt b/Documentation/filesystems/inotify.txt index 6d501903f68..59a919f1614 100644 --- a/Documentation/filesystems/inotify.txt +++ b/Documentation/filesystems/inotify.txt @@ -69,17 +69,135 @@ Prototypes: int inotify_rm_watch (int fd, __u32 mask); -(iii) Internal Kernel Implementation +(iii) Kernel Interface -Each inotify instance is associated with an inotify_device structure. +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 device and each associated inode. +off of each associated inotify_handle and each associated inode. -See fs/inotify.c for the locking and lifetime rules. +See fs/inotify.c and fs/inotify_user.c for the locking and lifetime rules. -(iv) Rationale +(vi) Rationale Q: What is the design decision behind not tying the watch to the open fd of the watched object? @@ -145,7 +263,7 @@ A: The poor user-space interface is the second biggest problem with dnotify. file descriptor-based one that allows basic file I/O and poll/select. Obtaining the fd and managing the watches could have been done either via a device file or a family of new system calls. We decided to implement a - family of system calls because that is the preffered approach for new kernel + family of system calls because that is the preferred approach for new kernel interfaces. The only real difference was whether we wanted to use open(2) and ioctl(2) or a couple of new system calls. System calls beat ioctls. |