btrfs: track exclusive filesystem operation in flags

There are several operations, usually started from ioctls, that cannot
run concurrently. The status is tracked in
mutually_exclusive_operation_running as an atomic_t. We can easily track
the status as one of the per-filesystem flag bits with same
synchronization guarantees.

The conversion replaces:

* atomic_xchg(..., 1)    ->   test_and_set_bit(FLAG, ...)
* atomic_set(..., 0)     ->   clear_bit(FLAG, ...)

Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index e9d7711..70631d7 100644 (file)
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -705,6 +705,11 @@ struct btrfs_delayed_root;
 #define BTRFS_FS_BTREE_ERR                     11
 #define BTRFS_FS_LOG1_ERR                      12
 #define BTRFS_FS_LOG2_ERR                      13
+/*
+ * Indicate that a whole-filesystem exclusive operation is running
+ * (device replace, resize, device add/delete, balance)
+ */
+#define BTRFS_FS_EXCL_OP                       14
 
 struct btrfs_fs_info {
        u8 fsid[BTRFS_FSID_SIZE];
@@ -1070,8 +1075,6 @@ struct btrfs_fs_info {
        /* device replace state */
        struct btrfs_dev_replace dev_replace;
 
-       atomic_t mutually_exclusive_operation_running;
-
        struct percpu_counter bio_counter;
        wait_queue_head_t replace_wait;
 

diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
index e653921..de7b2c8 100644 (file)
--- a/fs/btrfs/dev-replace.c
+++ b/fs/btrfs/dev-replace.c
@@ -784,8 +784,7 @@ int btrfs_resume_dev_replace_async(struct btrfs_fs_info *fs_info)
        }
        btrfs_dev_replace_unlock(dev_replace, 1);
 
-       WARN_ON(atomic_xchg(
-               &fs_info->mutually_exclusive_operation_running, 1));
+       WARN_ON(test_and_set_bit(BTRFS_FS_EXCL_OP, &fs_info->flags));
        task = kthread_run(btrfs_dev_replace_kthread, fs_info, "btrfs-devrepl");
        return PTR_ERR_OR_ZERO(task);
 }
@@ -814,7 +813,7 @@ static int btrfs_dev_replace_kthread(void *data)
                        (unsigned int)progress);
        }
        btrfs_dev_replace_continue_on_mount(fs_info);
-       atomic_set(&fs_info->mutually_exclusive_operation_running, 0);
+       clear_bit(BTRFS_FS_EXCL_OP, &fs_info->flags);
 
        return 0;
 }

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index dabfc7a..a29dc3f 100644 (file)
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1504,7 +1504,7 @@ static noinline int btrfs_ioctl_resize(struct file *file,
        if (ret)
                return ret;
 
-       if (atomic_xchg(&fs_info->mutually_exclusive_operation_running, 1)) {
+       if (test_and_set_bit(BTRFS_FS_EXCL_OP, &fs_info->flags)) {
                mnt_drop_write_file(file);
                return BTRFS_ERROR_DEV_EXCL_RUN_IN_PROGRESS;
        }
@@ -1619,7 +1619,7 @@ out_free:
        kfree(vol_args);
 out:
        mutex_unlock(&fs_info->volume_mutex);
-       atomic_set(&fs_info->mutually_exclusive_operation_running, 0);
+       clear_bit(BTRFS_FS_EXCL_OP, &fs_info->flags);
        mnt_drop_write_file(file);
        return ret;
 }
@@ -2661,7 +2661,7 @@ static long btrfs_ioctl_add_dev(struct btrfs_fs_info *fs_info, void __user *arg)
        if (!capable(CAP_SYS_ADMIN))
                return -EPERM;
 
-       if (atomic_xchg(&fs_info->mutually_exclusive_operation_running, 1))
+       if (test_and_set_bit(BTRFS_FS_EXCL_OP, &fs_info->flags))
                return BTRFS_ERROR_DEV_EXCL_RUN_IN_PROGRESS;
 
        mutex_lock(&fs_info->volume_mutex);
@@ -2680,7 +2680,7 @@ static long btrfs_ioctl_add_dev(struct btrfs_fs_info *fs_info, void __user *arg)
        kfree(vol_args);
 out:
        mutex_unlock(&fs_info->volume_mutex);
-       atomic_set(&fs_info->mutually_exclusive_operation_running, 0);
+       clear_bit(BTRFS_FS_EXCL_OP, &fs_info->flags);
        return ret;
 }
 
@@ -2708,7 +2708,7 @@ static long btrfs_ioctl_rm_dev_v2(struct file *file, void __user *arg)
        if (vol_args->flags & ~BTRFS_VOL_ARG_V2_FLAGS_SUPPORTED)
                return -EOPNOTSUPP;
 
-       if (atomic_xchg(&fs_info->mutually_exclusive_operation_running, 1)) {
+       if (test_and_set_bit(BTRFS_FS_EXCL_OP, &fs_info->flags)) {
                ret = BTRFS_ERROR_DEV_EXCL_RUN_IN_PROGRESS;
                goto out;
        }
@@ -2721,7 +2721,7 @@ static long btrfs_ioctl_rm_dev_v2(struct file *file, void __user *arg)
                ret = btrfs_rm_device(fs_info, vol_args->name, 0);
        }
        mutex_unlock(&fs_info->volume_mutex);
-       atomic_set(&fs_info->mutually_exclusive_operation_running, 0);
+       clear_bit(BTRFS_FS_EXCL_OP, &fs_info->flags);
 
        if (!ret) {
                if (vol_args->flags & BTRFS_DEVICE_SPEC_BY_ID)
@@ -2752,7 +2752,7 @@ static long btrfs_ioctl_rm_dev(struct file *file, void __user *arg)
        if (ret)
                return ret;
 
-       if (atomic_xchg(&fs_info->mutually_exclusive_operation_running, 1)) {
+       if (test_and_set_bit(BTRFS_FS_EXCL_OP, &fs_info->flags)) {
                ret = BTRFS_ERROR_DEV_EXCL_RUN_IN_PROGRESS;
                goto out_drop_write;
        }
@@ -2772,7 +2772,7 @@ static long btrfs_ioctl_rm_dev(struct file *file, void __user *arg)
                btrfs_info(fs_info, "disk deleted %s", vol_args->name);
        kfree(vol_args);
 out:
-       atomic_set(&fs_info->mutually_exclusive_operation_running, 0);
+       clear_bit(BTRFS_FS_EXCL_OP, &fs_info->flags);
 out_drop_write:
        mnt_drop_write_file(file);
 
@@ -4442,13 +4442,11 @@ static long btrfs_ioctl_dev_replace(struct btrfs_fs_info *fs_info,
                        ret = -EROFS;
                        goto out;
                }
-               if (atomic_xchg(
-                       &fs_info->mutually_exclusive_operation_running, 1)) {
+               if (test_and_set_bit(BTRFS_FS_EXCL_OP, &fs_info->flags)) {
                        ret = BTRFS_ERROR_DEV_EXCL_RUN_IN_PROGRESS;
                } else {
                        ret = btrfs_dev_replace_by_ioctl(fs_info, p);
-                       atomic_set(
-                        &fs_info->mutually_exclusive_operation_running, 0);
+                       clear_bit(BTRFS_FS_EXCL_OP, &fs_info->flags);
                }
                break;
        case BTRFS_IOCTL_DEV_REPLACE_CMD_STATUS:
@@ -4643,7 +4641,7 @@ static long btrfs_ioctl_balance(struct file *file, void __user *arg)
                return ret;
 
 again:
-       if (!atomic_xchg(&fs_info->mutually_exclusive_operation_running, 1)) {
+       if (!test_and_set_bit(BTRFS_FS_EXCL_OP, &fs_info->flags)) {
                mutex_lock(&fs_info->volume_mutex);
                mutex_lock(&fs_info->balance_mutex);
                need_unlock = true;
@@ -4689,7 +4687,7 @@ again:
        }
 
 locked:
-       BUG_ON(!atomic_read(&fs_info->mutually_exclusive_operation_running));
+       BUG_ON(!test_bit(BTRFS_FS_EXCL_OP, &fs_info->flags));
 
        if (arg) {
                bargs = memdup_user(arg, sizeof(*bargs));
@@ -4745,11 +4743,10 @@ locked:
 
 do_balance:
        /*
-        * Ownership of bctl and mutually_exclusive_operation_running
+        * Ownership of bctl and filesystem flag BTRFS_FS_EXCL_OP
         * 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.
+        * free_fs_info.  The flag is cleared in __cancel_balance.
         */
        need_unlock = false;
 
@@ -4769,7 +4766,7 @@ 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);
+               clear_bit(BTRFS_FS_EXCL_OP, &fs_info->flags);
 out:
        mnt_drop_write_file(file);
        return ret;

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index df50a63..2e425a9 100644 (file)
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -3761,7 +3761,7 @@ static void __cancel_balance(struct btrfs_fs_info *fs_info)
        if (ret)
                btrfs_handle_fs_error(fs_info, ret, NULL);
 
-       atomic_set(&fs_info->mutually_exclusive_operation_running, 0);
+       clear_bit(BTRFS_FS_EXCL_OP, &fs_info->flags);
 }
 
 /* Non-zero return value signifies invalidity */
@@ -3941,7 +3941,7 @@ out:
                __cancel_balance(fs_info);
        else {
                kfree(bctl);
-               atomic_set(&fs_info->mutually_exclusive_operation_running, 0);
+               clear_bit(BTRFS_FS_EXCL_OP, &fs_info->flags);
        }
        return ret;
 }
@@ -4031,7 +4031,7 @@ 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));
+       WARN_ON(test_and_set_bit(BTRFS_FS_EXCL_OP, &fs_info->flags));
 
        mutex_lock(&fs_info->volume_mutex);
        mutex_lock(&fs_info->balance_mutex);