From: Wang Shilong <wangsl-fnst@xxxxxxxxxxxxxx>
The original code only has one spin_lock 'qgroup_lock' to protect
quota configurations on memory, if we want to add a BTRFS_QGROUP_INFO_KEY,
it will be added to Btree firstly and then update quota configuration
on memory,this case works ok just because of Btrfs internal btree lock.
However, if we want to add a BTRFS_QGROUP_RELATION_KEY, this will cause
problems, in fact,we need to check 'src' and 'dst' before, without an extra lock,
race conditions can not be avoided.
Holding mutex_lock, we can have the check before operations in safety.
Besides, we can remove some spin_lock usages and ease the burdern
of the global spin_lock.
Signed-off-by: Wang Shilong <wangsl-fnst@xxxxxxxxxxxxxx>
Reviewed-by: Miao Xie <miaox@xxxxxxxxxxxxxx>
---
fs/btrfs/ctree.h | 1 +
fs/btrfs/disk-io.c | 1 +
fs/btrfs/ioctl.c | 13 ++++++++++---
3 files changed, 12 insertions(+), 3 deletions(-)
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 6e81860..a7fec8c 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1582,6 +1582,7 @@ struct btrfs_fs_info {
/* holds configuration and tracking. Protected by qgroup_lock */
struct rb_root qgroup_tree;
+ struct mutex quota_lock;
spinlock_t qgroup_lock;
/* list of dirty qgroups to be written at next commit */
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index fe82d08..4552f14 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2250,6 +2250,7 @@ int open_ctree(struct super_block *sb,
mutex_init(&fs_info->dev_replace.lock);
spin_lock_init(&fs_info->qgroup_lock);
+ mutex_init(&fs_info->quota_lock);
fs_info->qgroup_tree = RB_ROOT;
INIT_LIST_HEAD(&fs_info->dirty_qgroups);
fs_info->qgroup_seq = 1;
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 222ce84..0b8ab81 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3693,6 +3693,7 @@ static long btrfs_ioctl_quota_ctl(struct file *file, void __user *arg)
goto drop_write;
}
+ mutex_lock(&root->fs_info->quota_lock);
down_read(&root->fs_info->subvol_sem);
if (sa->cmd != BTRFS_QUOTA_CTL_RESCAN) {
trans = btrfs_start_transaction(root, 2);
@@ -3728,6 +3729,7 @@ static long btrfs_ioctl_quota_ctl(struct file *file, void __user *arg)
out:
kfree(sa);
up_read(&root->fs_info->subvol_sem);
+ mutex_unlock(&root->fs_info->quota_lock);
drop_write:
mnt_drop_write_file(file);
return ret;
@@ -3754,6 +3756,7 @@ static long btrfs_ioctl_qgroup_assign(struct file *file, void __user *arg)
goto drop_write;
}
+ mutex_lock(&root->fs_info->quota_lock);
trans = btrfs_join_transaction(root);
if (IS_ERR(trans)) {
ret = PTR_ERR(trans);
@@ -3775,6 +3778,7 @@ static long btrfs_ioctl_qgroup_assign(struct file *file, void __user *arg)
out:
kfree(sa);
+ mutex_unlock(&root->fs_info->quota_lock);
drop_write:
mnt_drop_write_file(file);
return ret;
@@ -3805,11 +3809,11 @@ static long btrfs_ioctl_qgroup_create(struct file *file, void __user *arg)
ret = -EINVAL;
goto out;
}
-
+ mutex_lock(&root->fs_info->quota_lock);
trans = btrfs_join_transaction(root);
if (IS_ERR(trans)) {
ret = PTR_ERR(trans);
- goto out;
+ goto out_unlock;
}
/* FIXME: check if the IDs really exist */
@@ -3824,6 +3828,8 @@ static long btrfs_ioctl_qgroup_create(struct file *file, void __user *arg)
if (err && !ret)
ret = err;
+out_unlock:
+ mutex_unlock(&root->fs_info->quota_lock);
out:
kfree(sa);
drop_write:
@@ -3852,7 +3858,7 @@ static long btrfs_ioctl_qgroup_limit(struct file *file, void __user *arg)
ret = PTR_ERR(sa);
goto drop_write;
}
-
+ mutex_lock(&root->fs_info->quota_lock);
trans = btrfs_join_transaction(root);
if (IS_ERR(trans)) {
ret = PTR_ERR(trans);
@@ -3874,6 +3880,7 @@ static long btrfs_ioctl_qgroup_limit(struct file *file, void __user *arg)
out:
kfree(sa);
+ mutex_unlock(&root->fs_info->quota_lock);
drop_write:
mnt_drop_write_file(file);
return ret;
--
1.7.7.6
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