linux/fs/notify/fanotify/fanotify.h

#include <linux/fsnotify_backend.h>
#include <linux/path.h>
#include <linux/slab.h>

extern struct kmem_cache *fanotify_event_cachep;

/*
 * Lifetime of the structure differs for normal and permission events. In both
 * cases the structure is allocated in fanotify_handle_event(). For normal
 * events the structure is freed immediately after reporting it to userspace.
 * For permission events we free it only after we receive response from
 * userspace.
 */
struct fanotify_event_info {
	struct fsnotify_event fse;
	/*
	 * We hold ref to this path so it may be dereferenced at any point
	 * during this object's lifetime
	 */
	struct path path;
	struct pid *tgid;
#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
	u32 response;	/* userspace answer to question */
#endif
};

static inline struct fanotify_event_info *FANOTIFY_E(struct fsnotify_event *fse)
{
	return container_of(fse, struct fanotify_event_info, fse);
}
fsnotify: do not share events between notification groups Currently fsnotify framework creates one event structure for each notification event and links this event into all interested notification groups. This is done so that we save memory when several notification groups are interested in the event. However the need for event structure shared between inotify & fanotify bloats the event structure so the result is often higher memory consumption. Another problem is that fsnotify framework keeps path references with outstanding events so that fanotify can return open file descriptors with its events. This has the undesirable effect that filesystem cannot be unmounted while there are outstanding events - a regression for inotify compared to a situation before it was converted to fsnotify framework. For fanotify this problem is hard to avoid and users of fanotify should kind of expect this behavior when they ask for file descriptors from notified files. This patch changes fsnotify and its users to create separate event structure for each group. This allows for much simpler code (~400 lines removed by this patch) and also smaller event structures. For example on 64-bit system original struct fsnotify_event consumes 120 bytes, plus additional space for file name, additional 24 bytes for second and each subsequent group linking the event, and additional 32 bytes for each inotify group for private data. After the conversion inotify event consumes 48 bytes plus space for file name which is considerably less memory unless file names are long and there are several groups interested in the events (both of which are uncommon). Fanotify event fits in 56 bytes after the conversion (fanotify doesn't care about file names so its events don't have to have it allocated). A win unless there are four or more fanotify groups interested in the event. The conversion also solves the problem with unmount when only inotify is used as we don't have to grab path references for inotify events. [hughd@google.com: fanotify: fix corruption preventing startup] Signed-off-by: Jan Kara <jack@suse.cz> Reviewed-by: Christoph Hellwig <hch@lst.de> Cc: Eric Paris <eparis@parisplace.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 2014-01-21 23:48:14 +00:00			`#include <linux/fsnotify_backend.h>`
			`#include <linux/path.h>`
			`#include <linux/slab.h>`

			`extern struct kmem_cache *fanotify_event_cachep;`

fanotify: Fix use after free for permission events Currently struct fanotify_event_info has been destroyed immediately after reporting its contents to userspace. However that is wrong for permission events because those need to stay around until userspace provides response which is filled back in fanotify_event_info. So change to code to free permission events only after we have got the response from userspace. Reported-and-tested-by: Jiri Kosina <jkosina@suse.cz> Reported-and-tested-by: Dave Jones <davej@fedoraproject.org> Signed-off-by: Jan Kara <jack@suse.cz> 2014-01-28 20:38:06 +00:00			`/*`
			`* Lifetime of the structure differs for normal and permission events. In both`
			`* cases the structure is allocated in fanotify_handle_event(). For normal`
			`* events the structure is freed immediately after reporting it to userspace.`
			`* For permission events we free it only after we receive response from`
			`* userspace.`
			`*/`
fsnotify: do not share events between notification groups Currently fsnotify framework creates one event structure for each notification event and links this event into all interested notification groups. This is done so that we save memory when several notification groups are interested in the event. However the need for event structure shared between inotify & fanotify bloats the event structure so the result is often higher memory consumption. Another problem is that fsnotify framework keeps path references with outstanding events so that fanotify can return open file descriptors with its events. This has the undesirable effect that filesystem cannot be unmounted while there are outstanding events - a regression for inotify compared to a situation before it was converted to fsnotify framework. For fanotify this problem is hard to avoid and users of fanotify should kind of expect this behavior when they ask for file descriptors from notified files. This patch changes fsnotify and its users to create separate event structure for each group. This allows for much simpler code (~400 lines removed by this patch) and also smaller event structures. For example on 64-bit system original struct fsnotify_event consumes 120 bytes, plus additional space for file name, additional 24 bytes for second and each subsequent group linking the event, and additional 32 bytes for each inotify group for private data. After the conversion inotify event consumes 48 bytes plus space for file name which is considerably less memory unless file names are long and there are several groups interested in the events (both of which are uncommon). Fanotify event fits in 56 bytes after the conversion (fanotify doesn't care about file names so its events don't have to have it allocated). A win unless there are four or more fanotify groups interested in the event. The conversion also solves the problem with unmount when only inotify is used as we don't have to grab path references for inotify events. [hughd@google.com: fanotify: fix corruption preventing startup] Signed-off-by: Jan Kara <jack@suse.cz> Reviewed-by: Christoph Hellwig <hch@lst.de> Cc: Eric Paris <eparis@parisplace.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 2014-01-21 23:48:14 +00:00			`struct fanotify_event_info {`
			`struct fsnotify_event fse;`
			`/*`
			`* We hold ref to this path so it may be dereferenced at any point`
			`* during this object's lifetime`
			`*/`
			`struct path path;`
			`struct pid *tgid;`
			`#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS`
			`u32 response; /* userspace answer to question */`
			`#endif`
			`};`

			`static inline struct fanotify_event_info FANOTIFY_E(struct fsnotify_event fse)`
			`{`
			`return container_of(fse, struct fanotify_event_info, fse);`
			`}`