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Commit ff0b16a9 authored by Eric Paris's avatar Eric Paris
Browse files

fanotify: fscking all notification system 



fanotify is a novel file notification system which bases notification on
giving userspace both an event type (open, close, read, write) and an open
file descriptor to the object in question.  This should address a number of
races and problems with other notification systems like inotify and dnotify
and should allow the future implementation of blocking or access controlled
notification.  These are useful for on access scanners or hierachical storage
management schemes.

This patch just implements the basics of the fsnotify functions.

Signed-off-by: default avatarEric Paris <eparis@redhat.com>
parent 12ed2e36

fs/notify/Kconfig

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@@ -3,3 +3,4 @@ config FSNOTIFY 


source "fs/notify/dnotify/Kconfig"

source "fs/notify/inotify/Kconfig"

source "fs/notify/fanotify/Kconfig"

fs/notify/Makefile

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@@ -2,3 +2,4 @@ obj-$(CONFIG_FSNOTIFY) += fsnotify.o notification.o group.o inode_mark.o 


obj-y			+= dnotify/

obj-y			+= inotify/

obj-y			+= fanotify/

fs/notify/fanotify/Kconfig

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config FANOTIFY

	bool "Filesystem wide access notification"

	select FSNOTIFY

	default y

	---help---

	   Say Y here to enable fanotify suport.  fanotify is a file access

	   notification system which differs from inotify in that it sends

	   and open file descriptor to the userspace listener along with

	   the event.



	   If unsure, say Y.

fs/notify/fanotify/Makefile

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obj-$(CONFIG_FANOTIFY)		+= fanotify.o

fs/notify/fanotify/fanotify.c

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#include <linux/fdtable.h>

#include <linux/fsnotify_backend.h>

#include <linux/init.h>

#include <linux/kernel.h> /* UINT_MAX */

#include <linux/types.h>



#include "fanotify.h"



static int fanotify_handle_event(struct fsnotify_group *group, struct fsnotify_event *event)

{

	int ret;





	BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS);

	BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY);

	BUILD_BUG_ON(FAN_CLOSE_NOWRITE != FS_CLOSE_NOWRITE);

	BUILD_BUG_ON(FAN_CLOSE_WRITE != FS_CLOSE_WRITE);

	BUILD_BUG_ON(FAN_OPEN != FS_OPEN);

	BUILD_BUG_ON(FAN_EVENT_ON_CHILD != FS_EVENT_ON_CHILD);

	BUILD_BUG_ON(FAN_Q_OVERFLOW != FS_Q_OVERFLOW);



	pr_debug("%s: group=%p event=%p\n", __func__, group, event);



	ret = fsnotify_add_notify_event(group, event, NULL, NULL);



	return ret;

}



static bool fanotify_should_send_event(struct fsnotify_group *group, struct inode *inode,

				       struct vfsmount *mnt, __u32 mask, void *data,

				       int data_type)

{

	struct fsnotify_mark *fsn_mark;

	bool send;



	pr_debug("%s: group=%p inode=%p mask=%x data=%p data_type=%d\n",

		 __func__, group, inode, mask, data, data_type);



	/* sorry, fanotify only gives a damn about files and dirs */

	if (!S_ISREG(inode->i_mode) &&

	    !S_ISDIR(inode->i_mode))

		return false;



	/* if we don't have enough info to send an event to userspace say no */

	if (data_type != FSNOTIFY_EVENT_PATH)

		return false;



	fsn_mark = fsnotify_find_mark(group, inode);

	if (!fsn_mark)

		return false;



	/* if the event is for a child and this inode doesn't care about

	 * events on the child, don't send it! */

	if ((mask & FS_EVENT_ON_CHILD) &&

	    !(fsn_mark->mask & FS_EVENT_ON_CHILD)) {

		send = false;

	} else {

		/*

		 * We care about children, but do we care about this particular

		 * type of event?

		 */

		mask = (mask & ~FS_EVENT_ON_CHILD);

		send = (fsn_mark->mask & mask);

	}



	/* find took a reference */

	fsnotify_put_mark(fsn_mark);



	return send;

}



const struct fsnotify_ops fanotify_fsnotify_ops = {

	.handle_event = fanotify_handle_event,

	.should_send_event = fanotify_should_send_event,

	.free_group_priv = NULL,

	.free_event_priv = NULL,

	.freeing_mark = NULL,

};