[CRIU] [PATCH v4 04/12] gc: implement link remaps deletion

[Eugene Batalov]

2016-10-12 11:54 GMT+03:00 Pavel Emelyanov <xemul at virtuozzo.com>:

> On 09/11/2016 08:14 PM, Eugene Batalov wrote:
> > We reuse minimal subset of criu restore command logic sufficient
> > to locate all the link remaps in all ps tree mnt namespaces.
> > No ps tree processes are created but all the ps tree mnt
> > namespaces and mountpoints are created. After creation of ps
> > tree mnt namespaces each link remap is deleted in its namespace.
> >
> > Exact logic is the following:
> > 1. check_img_inventory() - prepare_pstree(). These calls are needed to
> >    initialize root_ns_mask that is used during ps tree mnt namespaces
> >    creation.
>
> The root_ns_mask() is set up only in prepare_pstree() (which does much
> more than just this). But what is check_img_inventory() for?
>

check_img_inventory() call is intended to check that criu dump files that
we pass to criu gc are supported and somewhat valid.
check_img_inventory() is also called in the beginning of criu restore and
cr_lazy_pages.
So it looks like we should have it in cr-gc.


>
> > 2. prepare_shared_fdinfo() - collect_remaps_and_regfiles(). These calls
> >    are needed to collect information about link remaps and reg files of
> >    ps tree from dump.
>
> Why prepare_shared_fdinfo() needed?
>

prepare_shared_fdinfo() is needed because
during collect_remaps_and_regfiles() call collect_one_regfile() is called
and collect_one_regfile() calls file_desc_add().


>
> > 3. gc_setup_mntns() (if needed) creates all the ps tree mnt namespaces
> >    and performs mounting of proper fs hierachies into them.
>
> The read_mntns_img() does this, no?
>

No. The whole logic of gc_setup_mntns() does this. The main component
of gc_setup_mntns() is prepare_mnt_ns() call that instantiates
all the ps tree mnt namespaces and their root file systems.


>
> > 4. prepare_remaps() call is needed to associate link remaps and reg
> >    files structs we've read from dump. It also works with ps tree fs
> >    so mnt namespaces should be created before this call.
> >
> > 5. gc_link_remaps() - delete all the link remaps in their mnt namespaces.
> >
> > Signed-off-by: Eugene Batalov <eabatalov89 at gmail.com>
> > ---
> >  criu/cr-gc.c             | 104 ++++++++++++++++++++++++++++++
> ++++++++++++++++-
> >  criu/files-reg.c         |  37 +++++++++++++++++
> >  criu/include/files-reg.h |   1 +
> >  3 files changed, 141 insertions(+), 1 deletion(-)
> >
> > diff --git a/criu/cr-gc.c b/criu/cr-gc.c
> > index bdd3723..e248e66 100644
> > --- a/criu/cr-gc.c
> > +++ b/criu/cr-gc.c
> > @@ -1,6 +1,108 @@
> > +#include <sched.h>
> > +#include <unistd.h>
> > +
> > +#include "criu-log.h"
> >  #include "crtools.h"
> > +#include "pstree.h"
> > +#include "files.h"
> > +#include "files-reg.h"
> > +#include "mount.h"
> > +#include "namespaces.h"
> > +#include "util.h"
> >
> > -int cr_gc(void)
> > +static int root_mntns = -1;
> > +
> > +static int gc_setup_mntns(void)
> > +{
> > +     if (mntns_maybe_create_roots() < 0)
> > +             return -1;
> > +
> > +     if (read_mnt_ns_img() < 0)
> > +             return -1;
> > +
> > +     if (root_ns_mask & CLONE_NEWNS) {
> > +             /* prepare_mnt_ns() expects that root mnt ns is already
> created */
> > +             if (unshare(CLONE_NEWNS)) {
> > +                     pr_perror("Couldn't create root mount
> namespace\n");
> > +                     return -1;
> > +             }
> > +
> > +             root_mntns = open_proc(PROC_SELF, "ns/mnt");
> > +             if (root_mntns < 0)
> > +                     return -1;
> > +     }
> > +
> > +     if (prepare_mnt_ns() < 0)
> > +             return -1;
> > +
> > +     return 0;
> > +}
> > +
> > +static int gc_cleanup_mntns(void)
> > +{
> > +     int ret = depopulate_roots_yard(root_mntns, false);
> > +
> > +     if ((root_mntns != -1) && close(root_mntns)) {
> > +             pr_perror("Couldn't close root mntns fd");
> > +             ret = -1;
> > +     }
> > +
> > +     return ret;
> > +}
> > +
> > +static int gc_do(void)
> >  {
> > +     if (gc_link_remaps() < 0)
> > +             return -1;
> > +
> >       return 0;
> >  }
> > +
> > +int cr_gc(void)
> > +{
> > +     int ret = 0;
> > +
> > +     if (check_img_inventory() < 0) {
> > +             ret = -1;
> > +             goto exit;
> > +     }
> > +
> > +     if (prepare_task_entries() < 0) {
> > +             ret = -1;
> > +             goto exit;
> > +     }
> > +
> > +     if (prepare_pstree() < 0) {
> > +             ret = -1;
> > +             goto exit;
> > +     }
> > +
> > +     if (prepare_shared_fdinfo() < 0) {
> > +             ret = -1;
> > +             goto exit;
> > +     }
> > +
> > +     if (collect_remaps_and_regfiles()) {
> > +             ret = -1;
> > +             goto exit;
> > +     }
> > +
> > +     if (gc_setup_mntns()) {
> > +             ret = -1;
> > +             goto exit;
> > +     }
> > +
> > +     if (prepare_remaps() < 0) {
> > +             ret = -1;
> > +             goto exit;
> > +     }
> > +
> > +     if (gc_do())
> > +             ret = -1;
> > +
> > +exit:
> > +     if (gc_cleanup_mntns())
> > +             ret = -1;
> > +
> > +     return ret;
> > +}
> > diff --git a/criu/files-reg.c b/criu/files-reg.c
> > index 45100f9..07e9772 100644
> > --- a/criu/files-reg.c
> > +++ b/criu/files-reg.c
> > @@ -712,6 +712,43 @@ static void __rollback_link_remaps(bool do_unlink)
> >  void delete_link_remaps(void) { __rollback_link_remaps(true); }
> >  void free_link_remaps(void) { __rollback_link_remaps(false); }
> >
> > +int gc_link_remaps(void)
> > +{
> > +     struct remap_info *ri;
> > +     struct file_remap *remap;
> > +
> > +     list_for_each_entry(ri, &remaps, list) {
> > +             if (ri->rfe->remap_type != REMAP_TYPE__LINKED)
> > +                     continue;
> > +
> > +             remap = ri->rfi->remap;
> > +             struct ns_id *remap_mntns = lookup_nsid_by_mnt_id(remap->
> rmnt_id);
> > +
> > +             if (!remap_mntns) {
> > +                     pr_err("Can't get remap %s mnt ns %d\n",
> > +                                     remap->rpath, remap->rmnt_id);
> > +                     return -1;
> > +             }
> > +
> > +             if (remap_mntns->nd->cflag != CLONE_NEWNS) {
> > +                     pr_err("Wrong clone flag of remap mntns %x
> (id:%d)",
> > +                                     remap_mntns->nd->cflag,
> remap->rmnt_id);
> > +                     return -1;
> > +             }
> > +
> > +             /*
> > +              * We are root ps tree item in restore cmd terms.
> > +              * All the mnt namespaces and their fds are created
> > +              * by root ps tree item on restore.
> > +              * So we can simply use mnt ns fds here.
> > +              */
> > +             if (clean_one_remap(remap, remap_mntns->mnt.root_fd))
> > +                     return -1;
> > +     }
> > +
> > +     return 0;
> > +}
> > +
> >  static int create_link_remap(char *path, int len, int lfd,
> >                               u32 *idp, struct ns_id *nsid)
> >  {
> > diff --git a/criu/include/files-reg.h b/criu/include/files-reg.h
> > index 6cc2454..ff54303 100644
> > --- a/criu/include/files-reg.h
> > +++ b/criu/include/files-reg.h
> > @@ -52,6 +52,7 @@ extern void delete_link_remaps(void);
> >  extern void free_link_remaps(void);
> >  extern int prepare_remaps(void);
> >  extern void try_clean_remaps(void);
> > +extern int gc_link_remaps(void);
> >
> >  extern int strip_deleted(struct fd_link *link);
> >
> >
>
>


-- 
Best regards,
Eugene Batalov.
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