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The flag IN_MASK_CREATE is introduced as a flag for inotiy_add_watch() which prevents inotify from modifying any existing watches when invoked. If the pathname specified in the call has a watched inode associated with it and IN_MASK_CREATE is specified, fail with an errno of EEXIST. Use of IN_MASK_CREATE with IN_MASK_ADD is reserved for future use and will return EINVAL. RATIONALE In the current implementation, there is no way to prevent inotify_add_watch() from modifying existing watch descriptors. Even if the caller keeps a record of all watch descriptors collected, this is only sufficient to detect that an existing watch descriptor may have been modified. The assumption that a particular path will map to the same inode over multiple calls to inotify_add_watch() cannot be made as files can be renamed or deleted. It is also not possible to assume that two distinct paths do no map to the same inode, due to hard-links or a dereferenced symbolic link. Further uses of inotify_add_watch() to revert the change may cause other watch descriptors to be modified or created, merely compunding the problem. There is currently no system call such as inotify_modify_watch() to explicity modify a watch descriptor, which would be able to revert unwanted changes. Thus the caller cannot guarantee to be able to revert any changes to existing watch decriptors. Additionally the caller cannot assume that the events that are associated with a watch descriptor are within the set requested, as any future calls to inotify_add_watch() may unintentionally modify a watch descriptor's mask. Thus it cannot currently be guaranteed that a watch descriptor will only generate events which have been requested. The program must filter events which come through its watch descriptor to within its expected range. Reviewed-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Henry Wilson <henry.wilson@acentic.com> Signed-off-by: Jan Kara <jack@suse.cz>
85 lines
3.2 KiB
C
85 lines
3.2 KiB
C
/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
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/*
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* Inode based directory notification for Linux
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*
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* Copyright (C) 2005 John McCutchan
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*/
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#ifndef _UAPI_LINUX_INOTIFY_H
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#define _UAPI_LINUX_INOTIFY_H
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/* For O_CLOEXEC and O_NONBLOCK */
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#include <linux/fcntl.h>
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#include <linux/types.h>
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/*
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* struct inotify_event - structure read from the inotify device for each event
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*
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* When you are watching a directory, you will receive the filename for events
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* such as IN_CREATE, IN_DELETE, IN_OPEN, IN_CLOSE, ..., relative to the wd.
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*/
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struct inotify_event {
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__s32 wd; /* watch descriptor */
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__u32 mask; /* watch mask */
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__u32 cookie; /* cookie to synchronize two events */
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__u32 len; /* length (including nulls) of name */
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char name[0]; /* stub for possible name */
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};
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/* the following are legal, implemented events that user-space can watch for */
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#define IN_ACCESS 0x00000001 /* File was accessed */
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#define IN_MODIFY 0x00000002 /* File was modified */
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#define IN_ATTRIB 0x00000004 /* Metadata changed */
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#define IN_CLOSE_WRITE 0x00000008 /* Writtable file was closed */
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#define IN_CLOSE_NOWRITE 0x00000010 /* Unwrittable file closed */
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#define IN_OPEN 0x00000020 /* File was opened */
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#define IN_MOVED_FROM 0x00000040 /* File was moved from X */
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#define IN_MOVED_TO 0x00000080 /* File was moved to Y */
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#define IN_CREATE 0x00000100 /* Subfile was created */
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#define IN_DELETE 0x00000200 /* Subfile was deleted */
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#define IN_DELETE_SELF 0x00000400 /* Self was deleted */
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#define IN_MOVE_SELF 0x00000800 /* Self was moved */
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/* the following are legal events. they are sent as needed to any watch */
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#define IN_UNMOUNT 0x00002000 /* Backing fs was unmounted */
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#define IN_Q_OVERFLOW 0x00004000 /* Event queued overflowed */
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#define IN_IGNORED 0x00008000 /* File was ignored */
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/* helper events */
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#define IN_CLOSE (IN_CLOSE_WRITE | IN_CLOSE_NOWRITE) /* close */
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#define IN_MOVE (IN_MOVED_FROM | IN_MOVED_TO) /* moves */
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/* special flags */
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#define IN_ONLYDIR 0x01000000 /* only watch the path if it is a directory */
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#define IN_DONT_FOLLOW 0x02000000 /* don't follow a sym link */
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#define IN_EXCL_UNLINK 0x04000000 /* exclude events on unlinked objects */
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#define IN_MASK_CREATE 0x10000000 /* only create watches */
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#define IN_MASK_ADD 0x20000000 /* add to the mask of an already existing watch */
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#define IN_ISDIR 0x40000000 /* event occurred against dir */
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#define IN_ONESHOT 0x80000000 /* only send event once */
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/*
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* All of the events - we build the list by hand so that we can add flags in
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* the future and not break backward compatibility. Apps will get only the
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* events that they originally wanted. Be sure to add new events here!
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*/
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#define IN_ALL_EVENTS (IN_ACCESS | IN_MODIFY | IN_ATTRIB | IN_CLOSE_WRITE | \
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IN_CLOSE_NOWRITE | IN_OPEN | IN_MOVED_FROM | \
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IN_MOVED_TO | IN_DELETE | IN_CREATE | IN_DELETE_SELF | \
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IN_MOVE_SELF)
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/* Flags for sys_inotify_init1. */
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#define IN_CLOEXEC O_CLOEXEC
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#define IN_NONBLOCK O_NONBLOCK
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/*
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* ioctl numbers: inotify uses 'I' prefix for all ioctls,
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* except historical FIONREAD, which is based on 'T'.
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*
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* INOTIFY_IOC_SETNEXTWD: set desired number of next created
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* watch descriptor.
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*/
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#define INOTIFY_IOC_SETNEXTWD _IOW('I', 0, __s32)
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#endif /* _UAPI_LINUX_INOTIFY_H */
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