[1/7] btrfs: optimize use of volume_mutex in btrfs_ioctl_resize()

Commit Message

Anand Jain Nov. 6, 2017, 8:36 a.m. UTC

We can push volume_mutex lock further down after the memory operation.

Signed-off-by: Anand Jain <[e-mail]>
---
 fs/btrfs/ioctl.c | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

Comments

David Sterba Nov. 6, 2017, 4:50 p.m. UTC | #1

On Mon, Nov 06, 2017 at 04:36:12PM +0800, Anand Jain wrote:
> We can push volume_mutex lock further down after the memory operation.

I'm a bit reluctant to apply any patches that cleanup volume_mutex as
it's going to be removed.
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Patch

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 09c95f1b07dc..2eb220213d63 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1470,7 +1470,6 @@  static noinline int btrfs_ioctl_resize(struct file *file,
 		return BTRFS_ERROR_DEV_EXCL_RUN_IN_PROGRESS;
 	}
 
-	mutex_lock(&fs_info->volume_mutex);
 	vol_args = memdup_user(arg, sizeof(*vol_args));
 	if (IS_ERR(vol_args)) {
 		ret = PTR_ERR(vol_args);
@@ -1495,12 +1494,13 @@  static noinline int btrfs_ioctl_resize(struct file *file,
 		btrfs_info(fs_info, "resizing devid %llu", devid);
 	}
 
+	mutex_lock(&fs_info->volume_mutex);
 	device = btrfs_find_device(fs_info, devid, NULL, NULL);
 	if (!device) {
 		btrfs_info(fs_info, "resizer unable to find device %llu",
 			   devid);
 		ret = -ENODEV;
-		goto out_free;
+		goto out_mutex;
 	}
 
 	if (!device->writeable) {
@@ -1508,7 +1508,7 @@  static noinline int btrfs_ioctl_resize(struct file *file,
 			   "resizer unable to apply on readonly device %llu",
 		       devid);
 		ret = -EPERM;
-		goto out_free;
+		goto out_mutex;
 	}
 
 	if (!strcmp(sizestr, "max"))
@@ -1524,13 +1524,13 @@  static noinline int btrfs_ioctl_resize(struct file *file,
 		new_size = memparse(sizestr, &retptr);
 		if (*retptr != '\0' || new_size == 0) {
 			ret = -EINVAL;
-			goto out_free;
+			goto out_mutex;
 		}
 	}
 
 	if (device->is_tgtdev_for_dev_replace) {
 		ret = -EPERM;
-		goto out_free;
+		goto out_mutex;
 	}
 
 	old_size = btrfs_device_get_total_bytes(device);
@@ -1538,24 +1538,24 @@  static noinline int btrfs_ioctl_resize(struct file *file,
 	if (mod < 0) {
 		if (new_size > old_size) {
 			ret = -EINVAL;
-			goto out_free;
+			goto out_mutex;
 		}
 		new_size = old_size - new_size;
 	} else if (mod > 0) {
 		if (new_size > ULLONG_MAX - old_size) {
 			ret = -ERANGE;
-			goto out_free;
+			goto out_mutex;
 		}
 		new_size = old_size + new_size;
 	}
 
 	if (new_size < SZ_256M) {
 		ret = -EINVAL;
-		goto out_free;
+		goto out_mutex;
 	}
 	if (new_size > device->bdev->bd_inode->i_size) {
 		ret = -EFBIG;
-		goto out_free;
+		goto out_mutex;
 	}
 
 	new_size = round_down(new_size, fs_info->sectorsize);
@@ -1567,7 +1567,7 @@  static noinline int btrfs_ioctl_resize(struct file *file,
 		trans = btrfs_start_transaction(root, 0);
 		if (IS_ERR(trans)) {
 			ret = PTR_ERR(trans);
-			goto out_free;
+			goto out_mutex;
 		}
 		ret = btrfs_grow_device(trans, device, new_size);
 		btrfs_commit_transaction(trans);
@@ -1575,10 +1575,11 @@  static noinline int btrfs_ioctl_resize(struct file *file,
 		ret = btrfs_shrink_device(device, new_size);
 	} /* equal, nothing need to do */
 
+out_mutex:
+	mutex_unlock(&fs_info->volume_mutex);
 out_free:
 	kfree(vol_args);
 out:
-	mutex_unlock(&fs_info->volume_mutex);
 	clear_bit(BTRFS_FS_EXCL_OP, &fs_info->flags);
 	mnt_drop_write_file(file);
 	return ret;