[v7,8/9] btrfs: Use sb_want_write() to protect label change.

Commit Message

Qu Wenruo Feb. 6, 2015, 5:45 a.m. UTC

Use the new vfs API sb_want_write() to do the write protection of the
label change transaction.

Signed-off-by: Qu Wenruo <[e-mail]>
---
v4:
  Newly introduced.
v5:
  Change to use sb_want_write().
v6:
  Move sb_want_write() at the beginning of the function.
v7:
  None
---
 fs/btrfs/sysfs.c | 22 +++++++++++++++-------
 1 file changed, 15 insertions(+), 7 deletions(-)

Patch

diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index b2e7bb4..7e548f7 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 +378,9 @@  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;
+	ret = sb_want_write(fs_info->sb);
+	if (ret)
+		return ret;
 
 	/*
 	 * p_len is the len until the first occurrence of either
@@ -386,12 +388,17 @@  static ssize_t btrfs_label_store(struct kobject *kobj,
 	 */
 	p_len = strcspn(buf, "\n");
 
-	if (p_len >= BTRFS_LABEL_SIZE)
-		return -EINVAL;
+	if (p_len >= BTRFS_LABEL_SIZE) {
+		ret = -EINVAL;
+		goto out;
+	}
+
 
 	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 +406,10 @@  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);