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

4 files changed, 231 insertions, 15 deletions

diff --git a/fs/fuse/control.c b/fs/fuse/control.c
index 99c99dfb0373..3773fd63d2f9 100644
--- a/fs/fuse/control.c
+++ b/fs/fuse/control.c
@@ -61,6 +61,121 @@ static ssize_t fuse_conn_waiting_read(struct file *file, char __user *buf,
         return simple_read_from_buffer(buf, len, ppos, tmp, size);
 }
 
+static ssize_t fuse_conn_limit_read(struct file *file, char __user *buf,
+                                    size_t len, loff_t *ppos, unsigned val)
+{
+        char tmp[32];
+        size_t size = sprintf(tmp, "%u\n", val);
+
+        return simple_read_from_buffer(buf, len, ppos, tmp, size);
+}
+
+static ssize_t fuse_conn_limit_write(struct file *file, const char __user *buf,
+                                     size_t count, loff_t *ppos, unsigned *val,
+                                     unsigned global_limit)
+{
+        unsigned long t;
+        char tmp[32];
+        unsigned limit = (1 << 16) - 1;
+        int err;
+
+        if (*ppos || count >= sizeof(tmp) - 1)
+                return -EINVAL;
+
+        if (copy_from_user(tmp, buf, count))
+                return -EINVAL;
+
+        tmp[count] = '\0';
+
+        err = strict_strtoul(tmp, 0, &t);
+        if (err)
+                return err;
+
+        if (!capable(CAP_SYS_ADMIN))
+                limit = min(limit, global_limit);
+
+        if (t > limit)
+                return -EINVAL;
+
+        *val = t;
+
+        return count;
+}
+
+static ssize_t fuse_conn_max_background_read(struct file *file,
+                                             char __user *buf, size_t len,
+                                             loff_t *ppos)
+{
+        struct fuse_conn *fc;
+        unsigned val;
+
+        fc = fuse_ctl_file_conn_get(file);
+        if (!fc)
+                return 0;
+
+        val = fc->max_background;
+        fuse_conn_put(fc);
+
+        return fuse_conn_limit_read(file, buf, len, ppos, val);
+}
+
+static ssize_t fuse_conn_max_background_write(struct file *file,
+                                              const char __user *buf,
+                                              size_t count, loff_t *ppos)
+{
+        unsigned val;
+        ssize_t ret;
+
+        ret = fuse_conn_limit_write(file, buf, count, ppos, &val,
+                                    max_user_bgreq);
+        if (ret > 0) {
+                struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
+                if (fc) {
+                        fc->max_background = val;
+                        fuse_conn_put(fc);
+                }
+        }
+
+        return ret;
+}
+
+static ssize_t fuse_conn_congestion_threshold_read(struct file *file,
+                                                   char __user *buf, size_t len,
+                                                   loff_t *ppos)
+{
+        struct fuse_conn *fc;
+        unsigned val;
+
+        fc = fuse_ctl_file_conn_get(file);
+        if (!fc)
+                return 0;
+
+        val = fc->congestion_threshold;
+        fuse_conn_put(fc);
+
+        return fuse_conn_limit_read(file, buf, len, ppos, val);
+}
+
+static ssize_t fuse_conn_congestion_threshold_write(struct file *file,
+                                                    const char __user *buf,
+                                                    size_t count, loff_t *ppos)
+{
+        unsigned val;
+        ssize_t ret;
+
+        ret = fuse_conn_limit_write(file, buf, count, ppos, &val,
+                                    max_user_congthresh);
+        if (ret > 0) {
+                struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
+                if (fc) {
+                        fc->congestion_threshold = val;
+                        fuse_conn_put(fc);
+                }
+        }
+
+        return ret;
+}
+
 static const struct file_operations fuse_ctl_abort_ops = {
         .open = nonseekable_open,
         .write = fuse_conn_abort_write,
@@ -71,6 +186,18 @@ static const struct file_operations fuse_ctl_waiting_ops = {
         .read = fuse_conn_waiting_read,
 };
 
+static const struct file_operations fuse_conn_max_background_ops = {
+        .open = nonseekable_open,
+        .read = fuse_conn_max_background_read,
+        .write = fuse_conn_max_background_write,
+};
+
+static const struct file_operations fuse_conn_congestion_threshold_ops = {
+        .open = nonseekable_open,
+        .read = fuse_conn_congestion_threshold_read,
+        .write = fuse_conn_congestion_threshold_write,
+};
+
 static struct dentry *fuse_ctl_add_dentry(struct dentry *parent,
                                           struct fuse_conn *fc,
                                           const char *name,
@@ -127,9 +254,14 @@ int fuse_ctl_add_conn(struct fuse_conn *fc)
                 goto err;
 
         if (!fuse_ctl_add_dentry(parent, fc, "waiting", S_IFREG | 0400, 1,
-                                NULL, &fuse_ctl_waiting_ops) ||
+                                 NULL, &fuse_ctl_waiting_ops) ||
             !fuse_ctl_add_dentry(parent, fc, "abort", S_IFREG | 0200, 1,
-                                 NULL, &fuse_ctl_abort_ops))
+                                 NULL, &fuse_ctl_abort_ops) ||
+            !fuse_ctl_add_dentry(parent, fc, "max_background", S_IFREG | 0600,
+                                 1, NULL, &fuse_conn_max_background_ops) ||
+            !fuse_ctl_add_dentry(parent, fc, "congestion_threshold",
+                                 S_IFREG | 0600, 1, NULL,
+                                 &fuse_conn_congestion_threshold_ops))
                 goto err;
 
         return 0;
@@ -156,7 +288,7 @@ void fuse_ctl_remove_conn(struct fuse_conn *fc)
                 d_drop(dentry);
                 dput(dentry);
         }
-        fuse_control_sb->s_root->d_inode->i_nlink--;
+        drop_nlink(fuse_control_sb->s_root->d_inode);
 }
 
 static int fuse_ctl_fill_super(struct super_block *sb, void *data, int silent)
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 6484eb75acd6..51d9e33d634f 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -250,7 +250,7 @@ static void queue_request(struct fuse_conn *fc, struct fuse_req *req)
 
 static void flush_bg_queue(struct fuse_conn *fc)
 {
-        while (fc->active_background < FUSE_MAX_BACKGROUND &&
+        while (fc->active_background < fc->max_background &&
                !list_empty(&fc->bg_queue)) {
                 struct fuse_req *req;
 
@@ -280,11 +280,11 @@ __releases(&fc->lock)
         list_del(&req->intr_entry);
         req->state = FUSE_REQ_FINISHED;
         if (req->background) {
-                if (fc->num_background == FUSE_MAX_BACKGROUND) {
+                if (fc->num_background == fc->max_background) {
                         fc->blocked = 0;
                         wake_up_all(&fc->blocked_waitq);
                 }
-                if (fc->num_background == FUSE_CONGESTION_THRESHOLD &&
+                if (fc->num_background == fc->congestion_threshold &&
                     fc->connected && fc->bdi_initialized) {
                         clear_bdi_congested(&fc->bdi, BLK_RW_SYNC);
                         clear_bdi_congested(&fc->bdi, BLK_RW_ASYNC);
@@ -410,9 +410,9 @@ static void fuse_request_send_nowait_locked(struct fuse_conn *fc,
 {
         req->background = 1;
         fc->num_background++;
-        if (fc->num_background == FUSE_MAX_BACKGROUND)
+        if (fc->num_background == fc->max_background)
                 fc->blocked = 1;
-        if (fc->num_background == FUSE_CONGESTION_THRESHOLD &&
+        if (fc->num_background == fc->congestion_threshold &&
             fc->bdi_initialized) {
                 set_bdi_congested(&fc->bdi, BLK_RW_SYNC);
                 set_bdi_congested(&fc->bdi, BLK_RW_ASYNC);
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 52b641fc0faf..fc9c79feb5f7 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -25,12 +25,6 @@
 /** Max number of pages that can be used in a single read request */
 #define FUSE_MAX_PAGES_PER_REQ 32
 
-/** Maximum number of outstanding background requests */
-#define FUSE_MAX_BACKGROUND 12
-
-/** Congestion starts at 75% of maximum */
-#define FUSE_CONGESTION_THRESHOLD (FUSE_MAX_BACKGROUND * 75 / 100)
-
 /** Bias for fi->writectr, meaning new writepages must not be sent */
 #define FUSE_NOWRITE INT_MIN
 
@@ -38,7 +32,7 @@
 #define FUSE_NAME_MAX 1024
 
 /** Number of dentries for each connection in the control filesystem */
-#define FUSE_CTL_NUM_DENTRIES 3
+#define FUSE_CTL_NUM_DENTRIES 5
 
 /** If the FUSE_DEFAULT_PERMISSIONS flag is given, the filesystem
     module will check permissions based on the file mode.  Otherwise no
@@ -55,6 +49,10 @@ extern struct list_head fuse_conn_list;
 /** Global mutex protecting fuse_conn_list and the control filesystem */
 extern struct mutex fuse_mutex;
 
+/** Module parameters */
+extern unsigned max_user_bgreq;
+extern unsigned max_user_congthresh;
+
 /** FUSE inode */
 struct fuse_inode {
         /** Inode data */
@@ -349,6 +347,12 @@ struct fuse_conn {
         /** rbtree of fuse_files waiting for poll events indexed by ph */
         struct rb_root polled_files;
 
+        /** Maximum number of outstanding background requests */
+        unsigned max_background;
+
+        /** Number of background requests at which congestion starts */
+        unsigned congestion_threshold;
+
         /** Number of requests currently in the background */
         unsigned num_background;
 
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: