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| author | Nikolay Borisov <nborisov@suse.com> | 2020-07-22 11:09:22 +0300 |
|---|---|---|
| committer | David Sterba <dsterba@suse.com> | 2020-10-07 12:12:15 +0200 |
| commit | f4cfa9bdd40c038ac901fbf3c57ab63e9e8eb949 (patch) | |
| tree | 7a20b38750670a960177ec071178ea99720e0801 /fs/btrfs/volumes.c | |
| parent | d16c702fe4f274bd77b47d3ab737eadcf24e0b93 (diff) | |
| download | linux-f4cfa9bdd40c038ac901fbf3c57ab63e9e8eb949.tar.gz | |
btrfs: use RCU for quick device check in btrfs_init_new_device
When adding a new device there's a mandatory check to see if a device is
being duplicated to the filesystem it's added to. Since this is a
read-only operations not necessary to take device_list_mutex and can simply
make do with an rcu-readlock.
Using just RCU is safe because there won't be another device add delete
running in parallel as btrfs_init_new_device is called only from
btrfs_ioctl_add_dev.
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs/btrfs/volumes.c')
| -rw-r--r-- | fs/btrfs/volumes.c | 9 |
1 files changed, 4 insertions, 5 deletions
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 29c6f0154c62..5449e3899e67 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -2515,16 +2515,15 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path filemap_write_and_wait(bdev->bd_inode->i_mapping); - mutex_lock(&fs_devices->device_list_mutex); - list_for_each_entry(device, &fs_devices->devices, dev_list) { + rcu_read_lock(); + list_for_each_entry_rcu(device, &fs_devices->devices, dev_list) { if (device->bdev == bdev) { ret = -EEXIST; - mutex_unlock( - &fs_devices->device_list_mutex); + rcu_read_unlock(); goto error; } } - mutex_unlock(&fs_devices->device_list_mutex); + rcu_read_unlock(); device = btrfs_alloc_device(fs_info, NULL, NULL); if (IS_ERR(device)) { |