Pavel Emelianov [xemul@xxxxxxxxxx] wrote: | sukadev@xxxxxxxxxx wrote: | > Pavel Emelianov [xemul@xxxxxxxxxx] wrote: | > | sukadev@xxxxxxxxxx wrote: | > | > Subject: [PATCH 08/17] Pid-NS(V3) Define/use pid->upid_list list. | > | > | > | > From: Sukadev Bhattiprolu <sukadev@xxxxxxxxxx> | > | > | > | > | > | > With multiple pid namespaces, a process would be known by several pid_t | > | > values, one in each pid namespace. To represent this, we introduce a | > | > 'struct upid' which associates a single pid_t value with a single pid | > | > namespace. | > | > | > | > We then replace the pid->nr field in 'struct pid' with a list of struct upid' | > | > entries (referred to as 'pid->upid_list'). This list represents the multiple | > | > pid_t values of the process, one in each namespace. The current patch adds | > | > just one element to this list, corresponding to 'init_pid_ns'. Subsequent | > | > patches implement multiple pid namespaces and add more elements to the list. | > | > | > | > The 'struct upid' also replaces 'struct pid' in the pid_hash table to enable us | > | > to find processes given a pid_t from any namespace (i.e we find 'struct upid' | > | > for a given pid_t and from the 'struct upid', we find the 'struct pid' of the | > | > process) | > | > | > | > We finally reimplement find_pid() and pid_to_nr() to use pid->upid_list | > | > and remove unused fields from 'struct pid'. | > | > | > | > Changelog: | > | > 2.6.21-mm2-pidns3: | > | > | > | > - 'struct upid' used to be called 'struct pid_nr' and a list of these | > | > were hanging off of 'struct pid'. So, we renamed 'struct pid_nr' | > | > and now hold them in a statically sized array in 'struct pid' since | > | > the number of 'struct upid's for a process is known at process- | > | > creation time. | > | > | > | > 2.6.21-rc3-mm2: | > | > | > | > - [Eric Biederman] Combine all logical changes into one patch | > | > - [Eric Biederman] Implement __pid_nr(pid_ns, pid) for use in procfs. | > | > (now called pid_to_nr_in_ns()). | > | > - [Serge Hallyn]: Remove (!pid_nr) check in free_pid_nr() | > | > | > | > Signed-off-by: Cedric Le Goater <clg@xxxxxxxxxx> | > | > Signed-off-by: Sukadev Bhattiprolu <sukadev@xxxxxxxxxx> | > | > --- | > | > fs/proc/array.c | 30 ++++++-- | > | > fs/proc/base.c | 9 ++ | > | > include/linux/init_task.h | 14 +++- | > | > include/linux/pid.h | 62 ++++++++++++++--- | > | > include/linux/pid_namespace.h | 15 ++++ | > | > kernel/fork.c | 2 | > | > kernel/pid.c | 145 +++++++++++++++++++++++++++++++++--------- | > | > 7 files changed, 220 insertions(+), 57 deletions(-) | > | > | > | > Index: lx26-22-rc4-mm2/include/linux/pid.h | > | > =================================================================== | > | > --- lx26-22-rc4-mm2.orig/include/linux/pid.h 2007-06-15 18:44:50.000000000 -0700 | > | > +++ lx26-22-rc4-mm2/include/linux/pid.h 2007-06-15 19:47:58.000000000 -0700 | > | > @@ -16,6 +16,25 @@ enum pid_type | > | > PIDTYPE_MAX | > | > }; | > | > | > | > +struct pid_namespace; | > | > + | > | > +/* | > | > + * A struct upid holds a process identifier (or pid->nr) for a given | > | > + * pid namespace. | > | > + * | > | > + * A list of 'struct upid' entries is stored in the struct pid. This list | > | > + * is used to get the process identifier associated with the pid | > | > + * namespace it is being seen from. | > | > + */ | > | > +struct upid | > | > +{ | > | > + /* Try to keep pid_chain in the same cacheline as nr for find_pid */ | > | > + struct hlist_node pid_chain; /* link hash collisions on pid_hash */ | > | > + int nr; /* user space pid number */ | > | > + struct pid_namespace *pid_ns; /* pid namespace in which nr is valid */ | > | > + struct pid *pid; /* back to task's unique kernel pid */ | > | > +}; | > | > + | > | > /* | > | > * What is struct pid? | > | > * | > | > @@ -48,12 +67,11 @@ enum pid_type | > | > struct pid | > | > { | > | > atomic_t count; | > | > - /* Try to keep pid_chain in the same cacheline as nr for find_pid */ | > | > - int nr; | > | > - struct hlist_node pid_chain; | > | > /* lists of tasks that use this pid */ | > | > struct hlist_head tasks[PIDTYPE_MAX]; | > | > struct rcu_head rcu; | > | > + int num_upids; | > | > + struct upid upid_list[1]; | > | | > | Further in your patches you define MAX_NESTED_PID_NS. What for, you | > | use the linked list here!? | > | > Hmm. I don't understand. upid_list[] is an array (and not a linked | > list). Are you saying the '_list' in 'upid_list' is misleading ? | | Oh, I see! You allocate all the upids in one chunk. I have missed | that, sorry :) | | > Placing a limit like MAX_NESTED_PID_NS simplifies allocation of | > 'struct pid'. | | How? If we have, say, 100-level namespace than we have to create | the sizeof(struct pid) + 100 * sizeof(struct upid) bytes. I should have been a little more clear. I was comparing this with my previous version which did not have the MAX_NESTED_PID_NS limit and allowed for arbitrary levels of nesting (100 or even 1000 :-). Allocating that kind of 'struct pid' is more complex and looks like an overkill at this time. With a limit like MAX_NESTED_PID_NS, we could in theory create that many pid caches, one for each level of nesting and use the appropriate cache in clone(). | | > | > | | > | > }; | > | > | > | > extern struct pid init_struct_pid; | > | | > | [snip] | > _______________________________________________ | > Containers mailing list | > Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx | > https://lists.linux-foundation.org/mailman/listinfo/containers | > | > _______________________________________________ | > Devel mailing list | > Devel@xxxxxxxxxx | > https://openvz.org/mailman/listinfo/devel | > _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers