Merge branch 'mutex-ops@next-for-chris' of git://github.com/idryomov/btrfs-unstable into linus

2 files changed, 86 insertions, 31 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 982c0b9ceea5..afbf3ac2079d 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1340,7 +1340,7 @@ static noinline int btrfs_ioctl_resize(struct file *file,
                         1)) {
                 pr_info("btrfs: dev add/delete/balance/replace/resize operation in progress\n");
                 mnt_drop_write_file(file);
-                return -EINPROGRESS;
+                return -EINVAL;
         }
 
         mutex_lock(&root->fs_info->volume_mutex);
@@ -1446,8 +1446,8 @@ out_free:
         kfree(vol_args);
 out:
         mutex_unlock(&root->fs_info->volume_mutex);
-        mnt_drop_write_file(file);
         atomic_set(&root->fs_info->mutually_exclusive_operation_running, 0);
+        mnt_drop_write_file(file);
         return ret;
 }
 
@@ -2186,19 +2186,20 @@ static int btrfs_ioctl_defrag(struct file *file, void __user *argp)
         struct btrfs_ioctl_defrag_range_args *range;
         int ret;
 
-        if (btrfs_root_readonly(root))
-                return -EROFS;
+        ret = mnt_want_write_file(file);
+        if (ret)
+                return ret;
 
         if (atomic_xchg(&root->fs_info->mutually_exclusive_operation_running,
                         1)) {
                 pr_info("btrfs: dev add/delete/balance/replace/resize operation in progress\n");
-                return -EINPROGRESS;
+                mnt_drop_write_file(file);
+                return -EINVAL;
         }
-        ret = mnt_want_write_file(file);
-        if (ret) {
-                atomic_set(&root->fs_info->mutually_exclusive_operation_running,
-                           0);
-                return ret;
+
+        if (btrfs_root_readonly(root)) {
+                ret = -EROFS;
+                goto out;
         }
 
         switch (inode->i_mode & S_IFMT) {
@@ -2250,8 +2251,8 @@ static int btrfs_ioctl_defrag(struct file *file, void __user *argp)
                 ret = -EINVAL;
         }
 out:
-        mnt_drop_write_file(file);
         atomic_set(&root->fs_info->mutually_exclusive_operation_running, 0);
+        mnt_drop_write_file(file);
         return ret;
 }
 
@@ -2266,7 +2267,7 @@ static long btrfs_ioctl_add_dev(struct btrfs_root *root, void __user *arg)
         if (atomic_xchg(&root->fs_info->mutually_exclusive_operation_running,
                         1)) {
                 pr_info("btrfs: dev add/delete/balance/replace/resize operation in progress\n");
-                return -EINPROGRESS;
+                return -EINVAL;
         }
 
         mutex_lock(&root->fs_info->volume_mutex);
@@ -2303,7 +2304,7 @@ static long btrfs_ioctl_rm_dev(struct file *file, void __user *arg)
                         1)) {
                 pr_info("btrfs: dev add/delete/balance/replace/resize operation in progress\n");
                 mnt_drop_write_file(file);
-                return -EINPROGRESS;
+                return -EINVAL;
         }
 
         mutex_lock(&root->fs_info->volume_mutex);
@@ -2319,8 +2320,8 @@ static long btrfs_ioctl_rm_dev(struct file *file, void __user *arg)
         kfree(vol_args);
 out:
         mutex_unlock(&root->fs_info->volume_mutex);
-        mnt_drop_write_file(file);
         atomic_set(&root->fs_info->mutually_exclusive_operation_running, 0);
+        mnt_drop_write_file(file);
         return ret;
 }
 
@@ -3440,8 +3441,8 @@ static long btrfs_ioctl_balance(struct file *file, void __user *arg)
         struct btrfs_fs_info *fs_info = root->fs_info;
         struct btrfs_ioctl_balance_args *bargs;
         struct btrfs_balance_control *bctl;
+        bool need_unlock; /* for mut. excl. ops lock */
         int ret;
-        int need_to_clear_lock = 0;
 
         if (!capable(CAP_SYS_ADMIN))
                 return -EPERM;
@@ -3450,14 +3451,61 @@ static long btrfs_ioctl_balance(struct file *file, void __user *arg)
         if (ret)
                 return ret;
 
-        mutex_lock(&fs_info->volume_mutex);
+again:
+        if (!atomic_xchg(&fs_info->mutually_exclusive_operation_running, 1)) {
+                mutex_lock(&fs_info->volume_mutex);
+                mutex_lock(&fs_info->balance_mutex);
+                need_unlock = true;
+                goto locked;
+        }
+
+        /*
+         * mut. excl. ops lock is locked.  Three possibilites:
+         *   (1) some other op is running
+         *   (2) balance is running
+         *   (3) balance is paused -- special case (think resume)
+         */
         mutex_lock(&fs_info->balance_mutex);
+        if (fs_info->balance_ctl) {
+                /* this is either (2) or (3) */
+                if (!atomic_read(&fs_info->balance_running)) {
+                        mutex_unlock(&fs_info->balance_mutex);
+                        if (!mutex_trylock(&fs_info->volume_mutex))
+                                goto again;
+                        mutex_lock(&fs_info->balance_mutex);
+
+                        if (fs_info->balance_ctl &&
+                            !atomic_read(&fs_info->balance_running)) {
+                                /* this is (3) */
+                                need_unlock = false;
+                                goto locked;
+                        }
+
+                        mutex_unlock(&fs_info->balance_mutex);
+                        mutex_unlock(&fs_info->volume_mutex);
+                        goto again;
+                } else {
+                        /* this is (2) */
+                        mutex_unlock(&fs_info->balance_mutex);
+                        ret = -EINPROGRESS;
+                        goto out;
+                }
+        } else {
+                /* this is (1) */
+                mutex_unlock(&fs_info->balance_mutex);
+                pr_info("btrfs: dev add/delete/balance/replace/resize operation in progress\n");
+                ret = -EINVAL;
+                goto out;
+        }
+
+locked:
+        BUG_ON(!atomic_read(&fs_info->mutually_exclusive_operation_running));
 
         if (arg) {
                 bargs = memdup_user(arg, sizeof(*bargs));
                 if (IS_ERR(bargs)) {
                         ret = PTR_ERR(bargs);
-                        goto out;
+                        goto out_unlock;
                 }
 
                 if (bargs->flags & BTRFS_BALANCE_RESUME) {
@@ -3477,13 +3525,10 @@ static long btrfs_ioctl_balance(struct file *file, void __user *arg)
                 bargs = NULL;
         }
 
-        if (atomic_xchg(&root->fs_info->mutually_exclusive_operation_running,
-                        1)) {
-                pr_info("btrfs: dev add/delete/balance/replace/resize operation in progress\n");
+        if (fs_info->balance_ctl) {
                 ret = -EINPROGRESS;
                 goto out_bargs;
         }
-        need_to_clear_lock = 1;
 
         bctl = kzalloc(sizeof(*bctl), GFP_NOFS);
         if (!bctl) {
@@ -3504,11 +3549,17 @@ static long btrfs_ioctl_balance(struct file *file, void __user *arg)
         }
 
 do_balance:
-        ret = btrfs_balance(bctl, bargs);
         /*
-         * bctl is freed in __cancel_balance or in free_fs_info if
-         * restriper was paused all the way until unmount
+         * Ownership of bctl and mutually_exclusive_operation_running
+         * goes to to btrfs_balance.  bctl is freed in __cancel_balance,
+         * or, if restriper was paused all the way until unmount, in
+         * free_fs_info.  mutually_exclusive_operation_running is
+         * cleared in __cancel_balance.
          */
+        need_unlock = false;
+
+        ret = btrfs_balance(bctl, bargs);
+
         if (arg) {
                 if (copy_to_user(arg, bargs, sizeof(*bargs)))
                         ret = -EFAULT;
@@ -3516,12 +3567,12 @@ do_balance:
 
 out_bargs:
         kfree(bargs);
-out:
-        if (need_to_clear_lock)
-                atomic_set(&root->fs_info->mutually_exclusive_operation_running,
-                           0);
+out_unlock:
         mutex_unlock(&fs_info->balance_mutex);
         mutex_unlock(&fs_info->volume_mutex);
+        if (need_unlock)
+                atomic_set(&fs_info->mutually_exclusive_operation_running, 0);
+out:
         mnt_drop_write_file(file);
         return ret;
 }
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 86279c37de64..9c84dbe64f18 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2959,6 +2959,8 @@ static void __cancel_balance(struct btrfs_fs_info *fs_info)
         unset_balance_control(fs_info);
         ret = del_balance_item(fs_info->tree_root);
         BUG_ON(ret);
+
+        atomic_set(&fs_info->mutually_exclusive_operation_running, 0);
 }
 
 void update_ioctl_balance_args(struct btrfs_fs_info *fs_info, int lock,
@@ -3138,8 +3140,10 @@ int btrfs_balance(struct btrfs_balance_control *bctl,
 out:
         if (bctl->flags & BTRFS_BALANCE_RESUME)
                 __cancel_balance(fs_info);
-        else
+        else {
                 kfree(bctl);
+                atomic_set(&fs_info->mutually_exclusive_operation_running, 0);
+        }
         return ret;
 }
 
@@ -3156,7 +3160,6 @@ static int balance_kthread(void *data)
                 ret = btrfs_balance(fs_info->balance_ctl, NULL);
         }
 
-        atomic_set(&fs_info->mutually_exclusive_operation_running, 0);
         mutex_unlock(&fs_info->balance_mutex);
         mutex_unlock(&fs_info->volume_mutex);
 
@@ -3179,7 +3182,6 @@ int btrfs_resume_balance_async(struct btrfs_fs_info *fs_info)
                 return 0;
         }
 
-        WARN_ON(atomic_xchg(&fs_info->mutually_exclusive_operation_running, 1));
         tsk = kthread_run(balance_kthread, fs_info, "btrfs-balance");
         if (IS_ERR(tsk))
                 return PTR_ERR(tsk);
@@ -3233,6 +3235,8 @@ int btrfs_recover_balance(struct btrfs_fs_info *fs_info)
         btrfs_balance_sys(leaf, item, &disk_bargs);
         btrfs_disk_balance_args_to_cpu(&bctl->sys, &disk_bargs);
 
+        WARN_ON(atomic_xchg(&fs_info->mutually_exclusive_operation_running, 1));
+
         mutex_lock(&fs_info->volume_mutex);
         mutex_lock(&fs_info->balance_mutex);