Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse:
  fuse: add fusectl interface to max_background
  fuse: limit user-specified values of max background requests
  fuse: use drop_nlink() instead of direct nlink manipulation
  fuse: document protocol version negotiation
  fuse: make the number of max background requests and congestion threshold tunable

1 files changed, 80 insertions, 0 deletions

diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index e5dbecd87b0f..6da947daabda 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -14,6 +14,7 @@
 #include <linux/seq_file.h>
 #include <linux/init.h>
 #include <linux/module.h>
+#include <linux/moduleparam.h>
 #include <linux/parser.h>
 #include <linux/statfs.h>
 #include <linux/random.h>
@@ -28,10 +29,34 @@ static struct kmem_cache *fuse_inode_cachep;
 struct list_head fuse_conn_list;
 DEFINE_MUTEX(fuse_mutex);
 
+static int set_global_limit(const char *val, struct kernel_param *kp);
+
+unsigned max_user_bgreq;
+module_param_call(max_user_bgreq, set_global_limit, param_get_uint,
+                  &max_user_bgreq, 0644);
+__MODULE_PARM_TYPE(max_user_bgreq, "uint");
+MODULE_PARM_DESC(max_user_bgreq,
+ "Global limit for the maximum number of backgrounded requests an "
+ "unprivileged user can set");
+
+unsigned max_user_congthresh;
+module_param_call(max_user_congthresh, set_global_limit, param_get_uint,
+                  &max_user_congthresh, 0644);
+__MODULE_PARM_TYPE(max_user_congthresh, "uint");
+MODULE_PARM_DESC(max_user_congthresh,
+ "Global limit for the maximum congestion threshold an "
+ "unprivileged user can set");
+
 #define FUSE_SUPER_MAGIC 0x65735546
 
 #define FUSE_DEFAULT_BLKSIZE 512
 
+/** Maximum number of outstanding background requests */
+#define FUSE_DEFAULT_MAX_BACKGROUND 12
+
+/** Congestion starts at 75% of maximum */
+#define FUSE_DEFAULT_CONGESTION_THRESHOLD (FUSE_DEFAULT_MAX_BACKGROUND * 3 / 4)
+
 struct fuse_mount_data {
         int fd;
         unsigned rootmode;
@@ -517,6 +542,8 @@ void fuse_conn_init(struct fuse_conn *fc)
         INIT_LIST_HEAD(&fc->bg_queue);
         INIT_LIST_HEAD(&fc->entry);
         atomic_set(&fc->num_waiting, 0);
+        fc->max_background = FUSE_DEFAULT_MAX_BACKGROUND;
+        fc->congestion_threshold = FUSE_DEFAULT_CONGESTION_THRESHOLD;
         fc->khctr = 0;
         fc->polled_files = RB_ROOT;
         fc->reqctr = 0;
@@ -727,6 +754,54 @@ static const struct super_operations fuse_super_operations = {
         .show_options   = fuse_show_options,
 };
 
+static void sanitize_global_limit(unsigned *limit)
+{
+        if (*limit == 0)
+                *limit = ((num_physpages << PAGE_SHIFT) >> 13) /
+                         sizeof(struct fuse_req);
+
+        if (*limit >= 1 << 16)
+                *limit = (1 << 16) - 1;
+}
+
+static int set_global_limit(const char *val, struct kernel_param *kp)
+{
+        int rv;
+
+        rv = param_set_uint(val, kp);
+        if (rv)
+                return rv;
+
+        sanitize_global_limit((unsigned *)kp->arg);
+
+        return 0;
+}
+
+static void process_init_limits(struct fuse_conn *fc, struct fuse_init_out *arg)
+{
+        int cap_sys_admin = capable(CAP_SYS_ADMIN);
+
+        if (arg->minor < 13)
+                return;
+
+        sanitize_global_limit(&max_user_bgreq);
+        sanitize_global_limit(&max_user_congthresh);
+
+        if (arg->max_background) {
+                fc->max_background = arg->max_background;
+
+                if (!cap_sys_admin && fc->max_background > max_user_bgreq)
+                        fc->max_background = max_user_bgreq;
+        }
+        if (arg->congestion_threshold) {
+                fc->congestion_threshold = arg->congestion_threshold;
+
+                if (!cap_sys_admin &&
+                    fc->congestion_threshold > max_user_congthresh)
+                        fc->congestion_threshold = max_user_congthresh;
+        }
+}
+
 static void process_init_reply(struct fuse_conn *fc, struct fuse_req *req)
 {
         struct fuse_init_out *arg = &req->misc.init_out;
@@ -736,6 +811,8 @@ static void process_init_reply(struct fuse_conn *fc, struct fuse_req *req)
         else {
                 unsigned long ra_pages;
 
+                process_init_limits(fc, arg);
+
                 if (arg->minor >= 6) {
                         ra_pages = arg->max_readahead / PAGE_CACHE_SIZE;
                         if (arg->flags & FUSE_ASYNC_READ)
@@ -1150,6 +1227,9 @@ static int __init fuse_init(void)
         if (res)
                 goto err_sysfs_cleanup;
 
+        sanitize_global_limit(&max_user_bgreq);
+        sanitize_global_limit(&max_user_congthresh);
+
         return 0;
 
  err_sysfs_cleanup: