Merge tag 'fscache-fixes-20220831' of git://git.kernel.org/pub/scm/linux/kernel/git...

Pull fscache/cachefiles fixes from David Howells:

 - Fix kdoc on fscache_use/unuse_cookie().

 - Fix the error returned by cachefiles_ondemand_copen() from an upcall
   result.

 - Fix the distribution of requests in on-demand mode in cachefiles to
   be fairer by cycling through them rather than picking the one with
   the lowest ID each time (IDs being reused).

* tag 'fscache-fixes-20220831' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs:
  cachefiles: make on-demand request distribution fairer
  cachefiles: fix error return code in cachefiles_ondemand_copen()
  fscache: fix misdocumented parameter

diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h
index 6cba2c6..2ad58c4 100644 (file)
--- a/fs/cachefiles/internal.h
+++ b/fs/cachefiles/internal.h
@@ -111,6 +111,7 @@ struct cachefiles_cache {
        char                            *tag;           /* cache binding tag */
        refcount_t                      unbind_pincount;/* refcount to do daemon unbind */
        struct xarray                   reqs;           /* xarray of pending on-demand requests */
+       unsigned long                   req_id_next;
        struct xarray                   ondemand_ids;   /* xarray for ondemand_id allocation */
        u32                             ondemand_id_next;
 };

diff --git a/fs/cachefiles/ondemand.c b/fs/cachefiles/ondemand.c
index 1fee702..0254ed3 100644 (file)
--- a/fs/cachefiles/ondemand.c
+++ b/fs/cachefiles/ondemand.c
@@ -158,9 +158,13 @@ int cachefiles_ondemand_copen(struct cachefiles_cache *cache, char *args)
 
        /* fail OPEN request if daemon reports an error */
        if (size < 0) {
-               if (!IS_ERR_VALUE(size))
-                       size = -EINVAL;
-               req->error = size;
+               if (!IS_ERR_VALUE(size)) {
+                       req->error = -EINVAL;
+                       ret = -EINVAL;
+               } else {
+                       req->error = size;
+                       ret = 0;
+               }
                goto out;
        }
 
@@ -238,14 +242,19 @@ ssize_t cachefiles_ondemand_daemon_read(struct cachefiles_cache *cache,
        unsigned long id = 0;
        size_t n;
        int ret = 0;
-       XA_STATE(xas, &cache->reqs, 0);
+       XA_STATE(xas, &cache->reqs, cache->req_id_next);
 
        /*
-        * Search for a request that has not ever been processed, to prevent
-        * requests from being processed repeatedly.
+        * Cyclically search for a request that has not ever been processed,
+        * to prevent requests from being processed repeatedly, and make
+        * request distribution fair.
         */
        xa_lock(&cache->reqs);
        req = xas_find_marked(&xas, UINT_MAX, CACHEFILES_REQ_NEW);
+       if (!req && cache->req_id_next > 0) {
+               xas_set(&xas, 0);
+               req = xas_find_marked(&xas, cache->req_id_next - 1, CACHEFILES_REQ_NEW);
+       }
        if (!req) {
                xa_unlock(&cache->reqs);
                return 0;
@@ -260,6 +269,7 @@ ssize_t cachefiles_ondemand_daemon_read(struct cachefiles_cache *cache,
        }
 
        xas_clear_mark(&xas, CACHEFILES_REQ_NEW);
+       cache->req_id_next = xas.xa_index + 1;
        xa_unlock(&cache->reqs);
 
        id = xas.xa_index;

diff --git a/include/linux/fscache.h b/include/linux/fscache.h
index 720874e..36e5dd8 100644 (file)
--- a/include/linux/fscache.h
+++ b/include/linux/fscache.h
@@ -258,7 +258,7 @@ struct fscache_cookie *fscache_acquire_cookie(struct fscache_volume *volume,
 
 /**
  * fscache_use_cookie - Request usage of cookie attached to an object
- * @object: Object description
+ * @cookie: The cookie representing the cache object
  * @will_modify: If cache is expected to be modified locally
  *
  * Request usage of the cookie attached to an object.  The caller should tell
@@ -274,7 +274,7 @@ static inline void fscache_use_cookie(struct fscache_cookie *cookie,
 
 /**
  * fscache_unuse_cookie - Cease usage of cookie attached to an object
- * @object: Object description
+ * @cookie: The cookie representing the cache object
  * @aux_data: Updated auxiliary data (or NULL)
  * @object_size: Revised size of the object (or NULL)
  *