9p: Replace the fidlist with an IDR

The p9_idpool being used to allocate the IDs uses an IDR to allocate
the IDs ... which we then keep in a doubly-linked list, rather than in
the IDR which allocated them.  We can use an IDR directly which saves
two pointers per p9_fid, and a tiny memory allocation per p9_client.

Link: http://lkml.kernel.org/r/20180711210225.19730-4-willy@infradead.org
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Cc: Eric Van Hensbergen <ericvh@gmail.com>
Cc: Ron Minnich <rminnich@sandia.gov>
Cc: Latchesar Ionkov <lucho@ionkov.net>
Signed-off-by: Dominique Martinet <dominique.martinet@cea.fr>

2 files changed, 19 insertions, 34 deletions

diff --git a/include/net/9p/client.h b/include/net/9p/client.h
index 7af9d769b97d..e405729cd1c7 100644
--- a/include/net/9p/client.h
+++ b/include/net/9p/client.h
@@ -27,6 +27,7 @@
 #define NET_9P_CLIENT_H
 
 #include <linux/utsname.h>
+#include <linux/idr.h>
 
 /* Number of requests per row */
 #define P9_ROW_MAXTAG 255
@@ -128,8 +129,7 @@ struct p9_req_t {
  * @proto_version: 9P protocol version to use
  * @trans_mod: module API instantiated with this client
  * @trans: tranport instance state and API
- * @fidpool: fid handle accounting for session
- * @fidlist: List of active fid handles
+ * @fids: All active FID handles
  * @tagpool - transaction id accounting for session
  * @reqs - 2D array of requests
  * @max_tag - current maximum tag id allocated
@@ -169,8 +169,7 @@ struct p9_client {
                 } tcp;
         } trans_opts;
 
-        struct p9_idpool *fidpool;
-        struct list_head fidlist;
+        struct idr fids;
 
         struct p9_idpool *tagpool;
         struct p9_req_t *reqs[P9_ROW_MAXTAG];
@@ -188,7 +187,6 @@ struct p9_client {
  * @iounit: the server reported maximum transaction size for this file
  * @uid: the numeric uid of the local user who owns this handle
  * @rdir: readdir accounting structure (allocated on demand)
- * @flist: per-client-instance fid tracking
  * @dlist: per-dentry fid tracking
  *
  * TODO: This needs lots of explanation.
@@ -204,7 +202,6 @@ struct p9_fid {
 
         void *rdir;
 
-        struct list_head flist;
         struct hlist_node dlist;        /* list of all fids attached to a dentry */
 };
 
diff --git a/net/9p/client.c b/net/9p/client.c
index 7c317d39bf62..cd33cf636c47 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -909,30 +909,29 @@ static struct p9_fid *p9_fid_create(struct p9_client *clnt)
 {
         int ret;
         struct p9_fid *fid;
-        unsigned long flags;
 
         p9_debug(P9_DEBUG_FID, "clnt %p\n", clnt);
         fid = kmalloc(sizeof(struct p9_fid), GFP_KERNEL);
         if (!fid)
                 return NULL;
 
-        ret = p9_idpool_get(clnt->fidpool);
-        if (ret < 0)
-                goto error;
-        fid->fid = ret;
-
         memset(&fid->qid, 0, sizeof(struct p9_qid));
         fid->mode = -1;
         fid->uid = current_fsuid();
         fid->clnt = clnt;
         fid->rdir = NULL;
-        spin_lock_irqsave(&clnt->lock, flags);
-        list_add(&fid->flist, &clnt->fidlist);
-        spin_unlock_irqrestore(&clnt->lock, flags);
+        fid->fid = 0;
 
-        return fid;
+        idr_preload(GFP_KERNEL);
+        spin_lock_irq(&clnt->lock);
+        ret = idr_alloc_u32(&clnt->fids, fid, &fid->fid, P9_NOFID - 1,
+                            GFP_NOWAIT);
+        spin_unlock_irq(&clnt->lock);
+        idr_preload_end();
+
+        if (!ret)
+                return fid;
 
-error:
         kfree(fid);
         return NULL;
 }
@@ -944,9 +943,8 @@ static void p9_fid_destroy(struct p9_fid *fid)
 
         p9_debug(P9_DEBUG_FID, "fid %d\n", fid->fid);
         clnt = fid->clnt;
-        p9_idpool_put(fid->fid, clnt->fidpool);
         spin_lock_irqsave(&clnt->lock, flags);
-        list_del(&fid->flist);
+        idr_remove(&clnt->fids, fid->fid);
         spin_unlock_irqrestore(&clnt->lock, flags);
         kfree(fid->rdir);
         kfree(fid);
@@ -1029,7 +1027,7 @@ struct p9_client *p9_client_create(const char *dev_name, char *options)
         memcpy(clnt->name, client_id, strlen(client_id) + 1);
 
         spin_lock_init(&clnt->lock);
-        INIT_LIST_HEAD(&clnt->fidlist);
+        idr_init(&clnt->fids);
 
         err = p9_tag_init(clnt);
         if (err < 0)
@@ -1049,18 +1047,12 @@ struct p9_client *p9_client_create(const char *dev_name, char *options)
                 goto destroy_tagpool;
         }
 
-        clnt->fidpool = p9_idpool_create();
-        if (IS_ERR(clnt->fidpool)) {
-                err = PTR_ERR(clnt->fidpool);
-                goto put_trans;
-        }
-
         p9_debug(P9_DEBUG_MUX, "clnt %p trans %p msize %d protocol %d\n",
                  clnt, clnt->trans_mod, clnt->msize, clnt->proto_version);
 
         err = clnt->trans_mod->create(clnt, dev_name, options);
         if (err)
-                goto destroy_fidpool;
+                goto put_trans;
 
         if (clnt->msize > clnt->trans_mod->maxsize)
                 clnt->msize = clnt->trans_mod->maxsize;
@@ -1073,8 +1065,6 @@ struct p9_client *p9_client_create(const char *dev_name, char *options)
 
 close_trans:
         clnt->trans_mod->close(clnt);
-destroy_fidpool:
-        p9_idpool_destroy(clnt->fidpool);
 put_trans:
         v9fs_put_trans(clnt->trans_mod);
 destroy_tagpool:
@@ -1087,7 +1077,8 @@ EXPORT_SYMBOL(p9_client_create);
 
 void p9_client_destroy(struct p9_client *clnt)
 {
-        struct p9_fid *fid, *fidptr;
+        struct p9_fid *fid;
+        int id;
 
         p9_debug(P9_DEBUG_MUX, "clnt %p\n", clnt);
 
@@ -1096,14 +1087,11 @@ void p9_client_destroy(struct p9_client *clnt)
 
         v9fs_put_trans(clnt->trans_mod);
 
-        list_for_each_entry_safe(fid, fidptr, &clnt->fidlist, flist) {
+        idr_for_each_entry(&clnt->fids, fid, id) {
                 pr_info("Found fid %d not clunked\n", fid->fid);
                 p9_fid_destroy(fid);
         }
 
-        if (clnt->fidpool)
-                p9_idpool_destroy(clnt->fidpool);
-
         p9_tag_cleanup(clnt);
 
         kfree(clnt);