[5/5] Btrfs: using rcu lock in the reader side of devices list

Message ID	4DAEB0CC.1000004@cn.fujitsu.com (mailing list archive)
State	New, archived
Headers	show Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by demeter1.kernel.org (8.14.4/8.14.3) with ESMTP id p3KA8aiw018834 for <patchwork-linux-btrfs@patchwork.kernel.org>; Wed, 20 Apr 2011 10:08:36 GMT Message-ID: <4DAEB0CC.1000004@cn.fujitsu.com> Date: Wed, 20 Apr 2011 18:09:16 +0800 From: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com> User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.15) Gecko/20110307 Fedora/3.1.9-0.39.b3pre.fc14 Thunderbird/3.1.9 MIME-Version: 1.0 To: Chris Mason <chris.mason@oracle.com> CC: LKML <linux-kernel@vger.kernel.org>, BTRFS <linux-btrfs@vger.kernel.org> Subject: [PATCH 5/5] Btrfs: using rcu lock in the reader side of devices list References: <4DAEB030.1070303@cn.fujitsu.com> In-Reply-To: <4DAEB030.1070303@cn.fujitsu.com> Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=UTF-8 Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index 5a70096..ea13c9f 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -1412,8 +1412,8 @@ static int btrfs_congested_fn(void *congested_data, int bdi_bits) struct btrfs_device *device; struct backing_dev_info *bdi; - mutex_lock(&info->fs_devices->device_list_mutex); - list_for_each_entry(device, &info->fs_devices->devices, dev_list) { + rcu_read_lock(); + list_for_each_entry_rcu(device, &info->fs_devices->devices, dev_list) { if (!device->bdev) continue; bdi = blk_get_backing_dev_info(device->bdev); @@ -1422,7 +1422,7 @@ static int btrfs_congested_fn(void *congested_data, int bdi_bits) break; } } - mutex_unlock(&info->fs_devices->device_list_mutex); + rcu_read_unlock(); return ret; } @@ -1436,8 +1436,9 @@ static void __unplug_io_fn(struct backing_dev_info *bdi, struct page *page) struct btrfs_fs_info *info; info = (struct btrfs_fs_info *)bdi->unplug_io_data; - mutex_lock(&info->fs_devices->device_list_mutex); - list_for_each_entry(device, &info->fs_devices->devices, dev_list) { + + rcu_read_lock(); + list_for_each_entry_rcu(device, &info->fs_devices->devices, dev_list) { if (!device->bdev) continue; @@ -1445,7 +1446,7 @@ static void __unplug_io_fn(struct backing_dev_info *bdi, struct page *page) if (bdi->unplug_io_fn) bdi->unplug_io_fn(bdi, page); } - mutex_unlock(&info->fs_devices->device_list_mutex); + rcu_read_unlock(); } static void btrfs_unplug_io_fn(struct backing_dev_info *bdi, struct page *page) @@ -2414,9 +2415,9 @@ int write_all_supers(struct btrfs_root *root, int max_mirrors) sb = &root->fs_info->super_for_commit; dev_item = &sb->dev_item; - mutex_lock(&root->fs_info->fs_devices->device_list_mutex); + rcu_read_lock(); head = &root->fs_info->fs_devices->devices; - list_for_each_entry(dev, head, dev_list) { + list_for_each_entry_rcu(dev, head, dev_list) { if (!dev->bdev) { total_errors++; continue; @@ -2449,7 +2450,7 @@ int write_all_supers(struct btrfs_root *root, int max_mirrors) } total_errors = 0; - list_for_each_entry(dev, head, dev_list) { + list_for_each_entry_rcu(dev, head, dev_list) { if (!dev->bdev) continue; if (!dev->in_fs_metadata || !dev->writeable) @@ -2459,7 +2460,7 @@ int write_all_supers(struct btrfs_root *root, int max_mirrors) if (ret) total_errors++; } - mutex_unlock(&root->fs_info->fs_devices->device_list_mutex); + rcu_read_unlock(); if (total_errors > max_errors) { printk(KERN_ERR "btrfs: %d errors while writing supers\n", total_errors); diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index f580a3a..c2f8920 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -275,8 +275,9 @@ static noinline int btrfs_ioctl_fitrim(struct file *file, void __user *arg) if (!capable(CAP_SYS_ADMIN)) return -EPERM; - mutex_lock(&fs_info->fs_devices->device_list_mutex); - list_for_each_entry(device, &fs_info->fs_devices->devices, dev_list) { + rcu_read_lock(); + list_for_each_entry_rcu(device, &fs_info->fs_devices->devices, + dev_list) { if (!device->bdev) continue; q = bdev_get_queue(device->bdev); @@ -286,7 +287,7 @@ static noinline int btrfs_ioctl_fitrim(struct file *file, void __user *arg) minlen); } } - mutex_unlock(&fs_info->fs_devices->device_list_mutex); + rcu_read_unlock(); if (!num_devices) return -EOPNOTSUPP; diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index f43b946..8998ce7 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -397,7 +397,7 @@ static noinline int device_list_add(const char *path, INIT_LIST_HEAD(&device->dev_alloc_list); mutex_lock(&fs_devices->device_list_mutex); - list_add(&device->dev_list, &fs_devices->devices); + list_add_rcu(&device->dev_list, &fs_devices->devices); mutex_unlock(&fs_devices->device_list_mutex); device->fs_devices = fs_devices; @@ -505,6 +505,29 @@ again: return 0; } +static void __free_device(struct work_struct *work) +{ + struct btrfs_device *device; + + device = container_of(work, struct btrfs_device, rcu_work); + + if (device->bdev) + blkdev_put(device->bdev, device->mode); + + kfree(device->name); + kfree(device); +} + +static void free_device(struct rcu_head *head) +{ + struct btrfs_device *device; + + device = container_of(head, struct btrfs_device, rcu); + + INIT_WORK(&device->rcu_work, __free_device); + schedule_work(&device->rcu_work); +} + static int __btrfs_close_devices(struct btrfs_fs_devices *fs_devices) { struct btrfs_device *device; @@ -514,18 +537,27 @@ static int __btrfs_close_devices(struct btrfs_fs_devices *fs_devices) mutex_lock(&fs_devices->device_list_mutex); list_for_each_entry(device, &fs_devices->devices, dev_list) { - if (device->bdev) { - blkdev_put(device->bdev, device->mode); + struct btrfs_device *new_device; + + if (device->bdev) fs_devices->open_devices--; - } + if (device->writeable) { list_del_init(&device->dev_alloc_list); fs_devices->rw_devices--; } - device->bdev = NULL; - device->writeable = 0; - device->in_fs_metadata = 0; + new_device = kmalloc(sizeof(*new_device), GFP_NOFS); + BUG_ON(!new_device); + memcpy(new_device, device, sizeof(*new_device)); + new_device->name = kstrdup(device->name, GFP_NOFS); + BUG_ON(!new_device->name); + new_device->bdev = NULL; + new_device->writeable = 0; + new_device->in_fs_metadata = 0; + list_replace_rcu(&device->dev_list, &new_device->dev_list); + + call_rcu(&device->rcu, free_device); } mutex_unlock(&fs_devices->device_list_mutex); @@ -1238,11 +1270,13 @@ int btrfs_rm_device(struct btrfs_root *root, char *device_path) struct block_device *bdev; struct buffer_head *bh = NULL; struct btrfs_super_block *disk_super; + struct btrfs_fs_devices *cur_devices; u64 all_avail; u64 devid; u64 num_devices; u8 *dev_uuid; int ret = 0; + bool clear_super = false; mutex_lock(&uuid_mutex); mutex_lock(&root->fs_info->volume_mutex); @@ -1328,6 +1362,7 @@ int btrfs_rm_device(struct btrfs_root *root, char *device_path) list_del_init(&device->dev_alloc_list); unlock_chunks(root); root->fs_info->fs_devices->rw_devices--; + clear_super = true; } ret = btrfs_shrink_device(device, 0); @@ -1338,16 +1373,15 @@ int btrfs_rm_device(struct btrfs_root *root, char *device_path) if (ret) goto error_undo; - device->in_fs_metadata = 0; - /* * the device list mutex makes sure that we don't change * the device list while someone else is writing out all * the device supers. */ + + cur_devices = device->fs_devices; mutex_lock(&root->fs_info->fs_devices->device_list_mutex); - list_del_init(&device->dev_list); - mutex_unlock(&root->fs_info->fs_devices->device_list_mutex); + list_del_rcu(&device->dev_list); device->fs_devices->num_devices--; @@ -1361,36 +1395,36 @@ int btrfs_rm_device(struct btrfs_root *root, char *device_path) if (device->bdev == root->fs_info->fs_devices->latest_bdev) root->fs_info->fs_devices->latest_bdev = next_device->bdev; - if (device->bdev) { - blkdev_put(device->bdev, device->mode); - device->bdev = NULL; + if (device->bdev) device->fs_devices->open_devices--; - } + + call_rcu(&device->rcu, free_device); + mutex_unlock(&root->fs_info->fs_devices->device_list_mutex); num_devices = btrfs_super_num_devices(&root->fs_info->super_copy) - 1; btrfs_set_super_num_devices(&root->fs_info->super_copy, num_devices); - if (device->fs_devices->open_devices == 0) { + if (cur_devices->open_devices == 0) { struct btrfs_fs_devices *fs_devices; fs_devices = root->fs_info->fs_devices; while (fs_devices) { - if (fs_devices->seed == device->fs_devices) + if (fs_devices->seed == cur_devices) break; fs_devices = fs_devices->seed; } - fs_devices->seed = device->fs_devices->seed; - device->fs_devices->seed = NULL; + fs_devices->seed = cur_devices->seed; + cur_devices->seed = NULL; lock_chunks(root); - __btrfs_close_devices(device->fs_devices); + __btrfs_close_devices(cur_devices); unlock_chunks(root); - free_fs_devices(device->fs_devices); + free_fs_devices(cur_devices); } /* * at this point, the device is zero sized. We want to * remove it from the devices list and zero out the old super */ - if (device->writeable) { + if (clear_super) { /* make sure this device isn't detected as part of * the FS anymore */ @@ -1399,8 +1433,6 @@ int btrfs_rm_device(struct btrfs_root *root, char *device_path) sync_dirty_buffer(bh); } - kfree(device->name); - kfree(device); ret = 0; error_brelse: @@ -1459,7 +1491,8 @@ static int btrfs_prepare_sprout(struct btrfs_trans_handle *trans, mutex_init(&seed_devices->device_list_mutex); mutex_lock(&root->fs_info->fs_devices->device_list_mutex); - list_splice_init(&fs_devices->devices, &seed_devices->devices); + list_splice_init_rcu(&fs_devices->devices, &seed_devices->devices, + synchronize_rcu); mutex_unlock(&root->fs_info->fs_devices->device_list_mutex); list_splice_init(&fs_devices->alloc_list, &seed_devices->alloc_list); @@ -1658,7 +1691,7 @@ int btrfs_init_new_device(struct btrfs_root *root, char *device_path) * half setup */ mutex_lock(&root->fs_info->fs_devices->device_list_mutex); - list_add(&device->dev_list, &root->fs_info->fs_devices->devices); + list_add_rcu(&device->dev_list, &root->fs_info->fs_devices->devices); list_add(&device->dev_alloc_list, &root->fs_info->fs_devices->alloc_list); root->fs_info->fs_devices->num_devices++; diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h index cc2eada..f1b2e4f 100644 --- a/fs/btrfs/volumes.h +++ b/fs/btrfs/volumes.h @@ -86,6 +86,8 @@ struct btrfs_device { u8 uuid[BTRFS_UUID_SIZE]; struct btrfs_work work; + struct rcu_head rcu; + struct work_struct rcu_work; }; struct btrfs_fs_devices {

[5/5] Btrfs: using rcu lock in the reader side of devices list

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