Hi Linus, This patch just adds some documentation about directory notifications. Cheers, Stephen -- Stephen Rothwell, Open Source Researcher, Linuxcare, Inc. +61-2-62628990 tel, +61-2-62628991 fax [EMAIL PROTECTED], http://www.linuxcare.com/ Linuxcare. Support for the revolution. diff -ruN 2.4.0-test11pre4/Documentation/00-INDEX 2.4.0-test11pre4-dnot/Documentation/00-INDEX --- 2.4.0-test11pre4/Documentation/00-INDEX Wed Feb 9 06:28:31 2000 +++ 2.4.0-test11pre4-dnot/Documentation/00-INDEX Mon Nov 13 22:01:52 2000 @@ -43,6 +43,8 @@ - info on the Digiboard PC/X{i,e,eve} multiport boards. digiepca.txt - info on Digi Intl. {PC,PCI,EISA}Xx and Xem series cards. +dnotify.txt + - info about directory notification in Linux. exception.txt - how Linux v2.2 handles exceptions without verify_area etc. fb/ diff -ruN 2.4.0-test11pre4/Documentation/dnotify.txt 2.4.0-test11pre4-dnot/Documentation/dnotify.txt --- 2.4.0-test11pre4/Documentation/dnotify.txt Thu Jan 1 10:00:00 1970 +++ 2.4.0-test11pre4-dnot/Documentation/dnotify.txt Tue Nov 14 19:36:17 2000 @@ -0,0 +1,92 @@ + Linux Directory Notification + ============================ + + Stephen Rothwell <[EMAIL PROTECTED]> + +The intention of directory notification is to allow user applications +to be notified when a directory, or any of the files in it, are changed. +The basic mechanism involves the application registering for notification +on a directory using a fcntl(2) call and the notifications themselves +being delivered using signals. + +The application decides which "events" it wants to be notified about. +The currently defined events are: + + DN_ACCESS A file in the directory was accessed (read) + DN_MODIFY A file in the directory was modified (write,truncate) + DN_CREATE A file was created in the directory + DN_DELETE A file was unlinked from directory + DN_RENAME A file in the directory was renamed + DN_ATTRIB A file in the directory had its attributes + changed (chmod,chown) + +Usually, the application must reregister after each notification, but +if DN_MULTISHOT is or'ed with the event mask, then the registration will +remain until explicitly removed (by registering for no events). + +By default, SIGIO will be delivered to the process and no other useful +information. However, if the F_SETSIG fcntl(2) call is used to let the +kernel know which signal to deliver, a siginfo structure will be passed to +the signal handler and the si_fd member of that structure will contain the +file descriptor associated with the direcory in which the event occured. + +Preferably the application will choose one of the real time signals +(SIGRTMIN + <n>) so that the notifications may be queued. This is +especially important if DN_MULTISHOT is specified. + +Implementation expectations (features and bugs :-)) +--------------------------- + +The notification should work for any local access to files even if the +actual file system is on a remote server. This implies that remote +access to files served by local user mode servers should be notified. +Also, remote accesses to files served by a local kernel NFS server should +be notified. + +In order to make the impact on the file system code as small as possible, +the problem of hard links to files has been ignored. So if a file (x) +exists in two directories (a and b) then a change to the file using the +name "a/x" should be notified to a program expecting notifications on +directory "a", but will not be notified to one expecting notifications on +directory "b". + +Also, files that are unlinked, will still cause notifications in the +last directory that they were linked to. + +Example +------- + + #define _GNU_SOURCE /* needed to get the defines */ + #include <fcntl.h> /* in glibc 2.2 this has the needed + values defined */ + #include <signal.h> + #include <stdio.h> + #include <unistd.h> + + static volatile int event_fd; + + static void handler(int sig, siginfo_t *si, void *data) + { + event_fd = si->si_fd; + } + + int main(void) + { + struct sigaction act; + int fd; + + act.sa_sigaction = handler; + sigemptyset(&act.sa_mask); + act.sa_flags = SA_SIGINFO; + sigaction(SIGRTMIN, &act, NULL); + + fd = open(".", O_RDONLY); + fcntl(fd, F_SETSIG, SIGRTMIN); + fcntl(fd, F_NOTIFY, DN_MODIFY|DN_CREATE|DN_MULTISHOT); + /* we will now be notified if any of the files + in "." is modified or new files are created */ + while (1) { + pause(); + printf("Got event on fd=%d\n", event_fd); + } + } - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] Please read the FAQ at http://www.tux.org/lkml/
