On Mon 06-10-14 22:09:12, Heinrich Schuchardt wrote: > On 06.10.2014 15:24, Jan Kara wrote: > >On Fri 03-10-14 20:16:30, Heinrich Schuchardt wrote: > >>The fanotify and the inotify API can be used to monitor changes of the file > >>system. > >> > >>System call ftruncate modifies files. Hence it should trigger the corresponding > >>fanotify (FAN_MODIFY) and inotify (IN_MODIFY) events. > > Hum, I would think that the appropriate event gets generated by > >fsnotify_change() called from notify_change()? > > > > Honza > > Hello Jan, > > thank you for reviewing. > > fsnotify_change() calls > fsnotify(inode, mask, inode, FSNOTIFY_EVENT_INODE, NULL, 0); > > fsnotify_modify() calls > fsnotify(inode, mask, path, FSNOTIFY_EVENT_PATH, NULL, 0); > > Only with FSNOTIFY_EVENT_PATH a mount is determined in fsnotify(). > > So a FAN_MODIFY event for a mount cannot occur. But I also did not > see a FAN_MODIFY event when watching a file either. Yeah, fanotify processes only FSNOTIFY_EVENT_PATH events (without a path it cannot create an fd to pass to userspace). > IN_MODIFY events are actually created. > > So would it be better to do the change in do_truncate and replace > the call to notify_change by a call to fsnotify_modify? > > I just had a look at > http://lxr.free-electrons.com/ident?i=notify_change > > There seem to be some other usages of notify_change that deserve > consideration, e.g. in ecryptfs_truncate(). Yeah, so the reason why we don't generate FSNOTIFY_EVENT_PATH in notify_change() is because we have only dentry available there. OTOH from a quick look it doesn't look impossible to pass path there from the callers. So I'd rather propagate path to notify_change() and generate also fanotify events there than generating truncate events for fanotify separately somewhere else... Honza > >>Signed-off-by: Heinrich Schuchardt <xypron.glpk@xxxxxx> > >>--- > >> fs/open.c | 2 ++ > >> 1 file changed, 2 insertions(+) > >> > >>diff --git a/fs/open.c b/fs/open.c > >>index d6fd3ac..e36f26e 100644 > >>--- a/fs/open.c > >>+++ b/fs/open.c > >>@@ -189,6 +189,8 @@ static long do_sys_ftruncate(unsigned int fd, loff_t length, int small) > >> error = security_path_truncate(&f.file->f_path); > >> if (!error) > >> error = do_truncate(dentry, length, ATTR_MTIME|ATTR_CTIME, f.file); > >>+ if (!error) > >>+ fsnotify_modify(f.file); > >> sb_end_write(inode->i_sb); > >> out_putf: > >> fdput(f); > >>-- > >>2.1.0 > >> > -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
