On Fri, Jan 30, 2015 at 05:20:53PM +0800, Qu Wenruo wrote:
> Use the new vfs API sb_want_write() to do the write protection of the
> label change transaction.
>
> Signed-off-by: Qu Wenruo <quwenruo@xxxxxxxxxxxxxx>
> ---
> v4:
> Newly introduced.
> v5:
> Change to use sb_want_write().
> ---
> fs/btrfs/sysfs.c | 16 +++++++++++-----
> 1 file changed, 11 insertions(+), 5 deletions(-)
>
> diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
> index b2e7bb4..3218245 100644
> --- a/fs/btrfs/sysfs.c
> +++ b/fs/btrfs/sysfs.c
> @@ -25,6 +25,7 @@
> #include <linux/bug.h>
> #include <linux/genhd.h>
> #include <linux/debugfs.h>
> +#include <linux/mount.h>
>
> #include "ctree.h"
> #include "disk-io.h"
> @@ -377,8 +378,6 @@ static ssize_t btrfs_label_store(struct kobject *kobj,
> int ret;
> size_t p_len;
>
> - if (fs_info->sb->s_flags & MS_RDONLY)
> - return -EROFS;
>
> /*
> * p_len is the len until the first occurrence of either
> @@ -389,9 +388,15 @@ static ssize_t btrfs_label_store(struct kobject *kobj,
> if (p_len >= BTRFS_LABEL_SIZE)
> return -EINVAL;
>
> + ret = sb_want_write(fs_info->sb);
> + if (ret)
> + return ret;
Please move the check to the beginning of the function, where the
original MS_RDONLY check was.
> +
> trans = btrfs_start_transaction(root, 0);
> - if (IS_ERR(trans))
> - return PTR_ERR(trans);
> + if (IS_ERR(trans)) {
> + ret = PTR_ERR(trans);
> + goto out;
> + }
>
> spin_lock(&root->fs_info->super_lock);
> memset(fs_info->super_copy->label, 0, BTRFS_LABEL_SIZE);
> @@ -399,9 +404,10 @@ static ssize_t btrfs_label_store(struct kobject *kobj,
> spin_unlock(&root->fs_info->super_lock);
> ret = btrfs_commit_transaction(trans, root);
>
> +out:
> + sb_drop_write(fs_info->sb);
> if (!ret)
> return len;
> -
> return ret;
> }
> BTRFS_ATTR_RW(label, btrfs_label_show, btrfs_label_store);
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