Re: [PATCH V4 3/8] namespaces: expose ns instance serial numbers in proc

On Aug 20, 2014 8:12 PM, "Richard Guy Briggs" <rgb(a)redhat.com&gt; wrote: > Expose the namespace instace serial numbers in the proc filesystem at > /proc/<pid>/ns/<ns>_snum. The link text gives the serial number in hex. What's the use case? I understand the utility of giving unique numbers to the audit code, but I don't think this part is necessary for that, and I'd like to understand what else will use this before committing to a duplicative API like this.

Note that this API is thoroughly incompatible with CRIU. If we do this, someone will ask for a namespace number namespace, and that way lies madness.

--Andy > > "snum" was chosen instead of "seq" for consistency with inum and there are a > number of other uses of "seq" in the namespace code. > > Suggested-by: Serge E. Hallyn <serge(a)hallyn.com&gt; > Signed-off-by: Richard Guy Briggs <rgb(a)redhat.com&gt; > --- > fs/proc/namespaces.c | 33 +++++++++++++++++++++++++-------- > 1 files changed, 25 insertions(+), 8 deletions(-) > > diff --git a/fs/proc/namespaces.c b/fs/proc/namespaces.c > index 8902609..e953e0a 100644 > --- a/fs/proc/namespaces.c > +++ b/fs/proc/namespaces.c > @@ -47,12 +47,15 @@ static char *ns_dname(struct dentry *dentry, char *buffer, int buflen) > struct inode *inode = dentry->d_inode; > const struct proc_ns_operations *ns_ops = PROC_I(inode)->ns.ns_ops; > > - return dynamic_dname(dentry, buffer, buflen, "%s:[%lu]", > - ns_ops->name, inode->i_ino); > + if (strstr(dentry->d_iname, "_snum")) > + return dynamic_dname(dentry, buffer, buflen, "%s_snum:[%llx]", > + ns_ops->name, ns_ops->snum(PROC_I(inode)->ns.ns)); > + else > + return dynamic_dname(dentry, buffer, buflen, "%s:[%lu]", > + ns_ops->name, inode->i_ino); > } > > -const struct dentry_operations ns_dentry_operations = > -{ > +const struct dentry_operations ns_dentry_operations = { > .d_delete = always_delete_dentry, > .d_dname = ns_dname, > }; > @@ -160,7 +163,10 @@ static int proc_ns_readlink(struct dentry *dentry, char __user *buffer, int bufl > if (!ns) > goto out_put_task; > > - snprintf(name, sizeof(name), "%s:[%u]", ns_ops->name, ns_ops->inum(ns)); > + if (strstr(dentry->d_iname, "_snum")) > + snprintf(name, sizeof(name), "%s_snum:[%llx]", ns_ops->name, ns_ops->snum(ns)); > + else > + snprintf(name, sizeof(name), "%s:[%u]", ns_ops->name, ns_ops->inum(ns)); > res = readlink_copy(buffer, buflen, name); > ns_ops->put(ns); > out_put_task: > @@ -210,16 +216,23 @@ static int proc_ns_dir_readdir(struct file *file, struct dir_context *ctx) > > if (!dir_emit_dots(file, ctx)) > goto out; > - if (ctx->pos >= 2 + ARRAY_SIZE(ns_entries)) > + if (ctx->pos >= 2 + 2 * ARRAY_SIZE(ns_entries)) > goto out; > entry = ns_entries + (ctx->pos - 2); > last = &ns_entries[ARRAY_SIZE(ns_entries) - 1]; > while (entry <= last) { > const struct proc_ns_operations *ops = *entry; > + char name[50]; > + > if (!proc_fill_cache(file, ctx, ops->name, strlen(ops->name), > proc_ns_instantiate, task, ops)) > break; > ctx->pos++; > + snprintf(name, sizeof(name), "%s_snum", ops->name); > + if (!proc_fill_cache(file, ctx, name, strlen(name), > + proc_ns_instantiate, task, ops)) > + break; > + ctx->pos++; > entry++; > } > out: > @@ -247,9 +260,13 @@ static struct dentry *proc_ns_dir_lookup(struct inode *dir, > > last = &ns_entries[ARRAY_SIZE(ns_entries)]; > for (entry = ns_entries; entry < last; entry++) { > - if (strlen((*entry)->name) != len) > + char name[50]; > + > + snprintf(name, sizeof(name), "%s_snum", (*entry)->name); > + if (strlen((*entry)->name) != len && strlen(name) != len) > continue; > - if (!memcmp(dentry->d_name.name, (*entry)->name, len)) > + if (!memcmp(dentry->d_name.name, (*entry)->name, len) > + || !memcmp(dentry->d_name.name, name, len)) > break; > } > if (entry == last) > -- > 1.7.1 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-api" in > the body of a message to majordomo(a)vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html