[PATCH V3 3/6] namespaces: expose ns instance serial numbers in proc

[Richard Guy Briggs]

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.

"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 <se...@hallyn.com>
Signed-off-by: Richard Guy Briggs <r...@redhat.com>
---
 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 9ae46b8..57fce90 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));
        len = strlen(name);
 
        if (len > buflen)
@@ -216,16 +222,23 @@ 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:
@@ -253,9 +266,13 @@ 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

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