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Message-ID: <4DAEB0CC.1000004@cn.fujitsu.com>
Date: Wed, 20 Apr 2011 18:09:16 +0800
From: Xiao Guangrong <xiaoguangrong@...fujitsu.com>
To: Chris Mason <chris.mason@...cle.com>
CC: LKML <linux-kernel@...r.kernel.org>,
BTRFS <linux-btrfs@...r.kernel.org>
Subject: [PATCH 5/5] Btrfs: using rcu lock in the reader side of devices list
fs_devices->devices is only updated on remove and add device paths, so we can
use rcu to protect it in the reader side
Signed-off-by: Xiao Guangrong <xiaoguangrong@...fujitsu.com>
---
fs/btrfs/disk-io.c | 21 +++++++------
fs/btrfs/ioctl.c | 7 ++--
fs/btrfs/volumes.c | 85 ++++++++++++++++++++++++++++++++++++----------------
fs/btrfs/volumes.h | 2 +
4 files changed, 76 insertions(+), 39 deletions(-)
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 {
--
1.7.4.4
--
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