Hi Tvrtko,
> > 1. Race in cache implementation.
>
> [snip]
>
> > I be believe it could be solved by introducing two more ignore mark
> > flags. The fist one to set before the scan starts. It could be cleaned
> > by write operation. The second one to ask fanotify to set ignore flags
> > only if the first flag is still set. In this case we will never have
> > file with not scanned file changes in cache.
>
> Interesting that you have also found this - I suspected it but did not
> actually got round verifying it.
>
> Another possible (and simpler) solution is to refuse (ignore) adding ignore
> marks if file (well inode) is opened for writing (inode->i_writecount > 0)?
> More or less this is the approach we use in Talpa.
I agree. It's simpler and more clear and doesn't require changing the
interface.
> > 2. As I understood it was intended to flush cache via FAN_MARK_FLUSH
> > flag but it is currently disabled and there is no notion about it in the
> > man page. There are cases when it is necessary to flush all cache, for
> > example on anti-malware bases update.
>
> Where do you see this as disabled?
In fanotify_mark syscall flags argument is checked and if FAN_MARK_FLUSH
bit is set then EINVAL error is returned.
include/linux/fanotify.h:
31 #define FAN_MARK_ADD 0x00000001
32 #define FAN_MARK_REMOVE 0x00000002
33 #define FAN_MARK_DONT_FOLLOW 0x00000004
34 #define FAN_MARK_ONLYDIR 0x00000008
35 #define FAN_MARK_MOUNT 0x00000010
36 #define FAN_MARK_IGNORED_MASK 0x00000020
37 #define FAN_MARK_IGNORED_SURV_MODIFY 0x00000040
38 #define FAN_MARK_FLUSH 0x00000080
39
40 #define FAN_ALL_MARK_FLAGS (FAN_MARK_ADD |\
41 FAN_MARK_REMOVE |\
42 FAN_MARK_DONT_FOLLOW |\
43 FAN_MARK_ONLYDIR |\
44 FAN_MARK_MOUNT |\
45 FAN_MARK_IGNORED_MASK |\
46 FAN_MARK_IGNORED_SURV_MODIFY)
fs/notify/fanotify/fanotify_user.c:
678 SYSCALL_DEFINE(fanotify_mark)(int fanotify_fd, unsigned int
flags,
679 __u64 mask, int dfd,
680 const char __user * pathname)
...
696 if (flags & ~FAN_ALL_MARK_FLAGS)
697 return -EINVAL;
Regards,
Vasily
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