On Thu, Mar 16, 2017 at 09:59:09PM -0700, Andrei Vagin wrote: > On Fri, Mar 10, 2017 at 11:16:56AM +0300, Cyrill Gorcunov wrote: > > Since it is possbile to have same number in tfd field (say > > file added, closed, then nother file dup'ed to same number > > and added back) it is imposible to distinguish such target > > files solely by their numbers. > > > > Strictly speaking regular applications don't need to recognize > > these targets at all but for checkpoint/restore sake we need > > to collect targets to be able to push them back on restore > > stage in a proper order. > > > > Thus lets add file position, inode and device number where > > this target lays. This three fields can be used as a primary > > key for sorting, and together with kcmp help CRIU can find > > out an exact file target (from the whole set of processes > > being checkpointed). > > > > Signed-off-by: Cyrill Gorcunov <gorcunov@xxxxxxxxxx> > > CC: Al Viro <viro@xxxxxxxxxxxxxxxxxx> > > CC: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxx> > > CC: Andrey Vagin <avagin@xxxxxxxxxx> > > CC: Pavel Emelyanov <xemul@xxxxxxxxxxxxx> > > CC: Michael Kerrisk <mtk.manpages@xxxxxxxxx> > > CC: Kir Kolyshkin <kir@xxxxxxxxxx> > > CC: Jason Baron <jbaron@xxxxxxxxxx> > > CC: Andy Lutomirski <luto@xxxxxxxxxxxxxx> > > --- > > Documentation/filesystems/proc.txt | 6 +++++- > > fs/eventpoll.c | 8 ++++++-- > > 2 files changed, 11 insertions(+), 3 deletions(-) > > > > Index: linux-ml.git/Documentation/filesystems/proc.txt > > =================================================================== > > --- linux-ml.git.orig/Documentation/filesystems/proc.txt > > +++ linux-ml.git/Documentation/filesystems/proc.txt > > @@ -1779,12 +1779,16 @@ pair provide additional information part > > pos: 0 > > flags: 02 > > mnt_id: 9 > > - tfd: 5 events: 1d data: ffffffffffffffff > > + tfd: 5 events: 1d data: ffffffffffffffff pos:0 ino:61af sdev:7 > > I think it may be better to print mnt_id instead of sdev, because there > may be two file descriptors opened from different bind mounts. Fetching mnt_id is not that cheap in compare with sdev: instead of straight dereference inode->i_sb->s_dev we will have to figure out mnt_id from file+path, and our primary key is from sdev+ino anyway, so until _really_ needed I prefer cheaper/simplier solution.
