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-rw-r--r--fs/super.c48
1 files changed, 47 insertions, 1 deletions
diff --git a/fs/super.c b/fs/super.c
index 1cb26a3..19eb70b 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -465,6 +465,48 @@ rescan:
}
EXPORT_SYMBOL(get_super);
+
+/**
+ * get_active_super - get an active reference to the superblock of a device
+ * @bdev: device to get the superblock for
+ *
+ * Scans the superblock list and finds the superblock of the file system
+ * mounted on the device given. Returns the superblock with an active
+ * reference and s_umount held exclusively or %NULL if none was found.
+ */
+struct super_block *get_active_super(struct block_device *bdev)
+{
+ struct super_block *sb;
+
+ if (!bdev)
+ return NULL;
+
+ spin_lock(&sb_lock);
+ list_for_each_entry(sb, &super_blocks, s_list) {
+ if (sb->s_bdev != bdev)
+ continue;
+
+ sb->s_count++;
+ spin_unlock(&sb_lock);
+ down_write(&sb->s_umount);
+ if (sb->s_root) {
+ spin_lock(&sb_lock);
+ if (sb->s_count > S_BIAS) {
+ atomic_inc(&sb->s_active);
+ sb->s_count--;
+ spin_unlock(&sb_lock);
+ return sb;
+ }
+ spin_unlock(&sb_lock);
+ }
+ up_write(&sb->s_umount);
+ put_super(sb);
+ yield();
+ spin_lock(&sb_lock);
+ }
+ spin_unlock(&sb_lock);
+ return NULL;
+}
struct super_block * user_get_super(dev_t dev)
{
@@ -527,11 +569,15 @@ int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
{
int retval;
int remount_rw;
-
+
+ if (sb->s_frozen != SB_UNFROZEN)
+ return -EBUSY;
+
#ifdef CONFIG_BLOCK
if (!(flags & MS_RDONLY) && bdev_read_only(sb->s_bdev))
return -EACCES;
#endif
+
if (flags & MS_RDONLY)
acct_auto_close(sb);
shrink_dcache_sb(sb);
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