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authorJan Kara <jack@suse.cz>2012-02-10 11:03:00 +0100
committerAl Viro <viro@zeniv.linux.org.uk>2012-02-13 20:45:38 -0500
commit6b6dc836a195e077e76977b6c020a73de411b46d (patch)
tree59920a3aab6db4997f6b7a95c753219bdc12bd64
parent074b85175a43a23fdbde60f55feea636e0bf0f85 (diff)
vfs: Provide function to get superblock and wait for it to thaw
In quota code we need to find a superblock corresponding to a device and wait for superblock to be unfrozen. However this waiting has to happen without s_umount semaphore because that is required for superblock to thaw. So provide a function in VFS for this to keep dances with s_umount where they belong. [AV: implementation switched to saner variant] Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
-rw-r--r--fs/super.c22
-rw-r--r--include/linux/fs.h1
2 files changed, 23 insertions, 0 deletions
diff --git a/fs/super.c b/fs/super.c
index 6015c02296b..6277ec6cb60 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -634,6 +634,28 @@ rescan:
EXPORT_SYMBOL(get_super);
/**
+ * get_super_thawed - get thawed 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. The superblock is returned once it is thawed
+ * (or immediately if it was not frozen). %NULL is returned if no match
+ * is found.
+ */
+struct super_block *get_super_thawed(struct block_device *bdev)
+{
+ while (1) {
+ struct super_block *s = get_super(bdev);
+ if (!s || s->s_frozen == SB_UNFROZEN)
+ return s;
+ up_read(&s->s_umount);
+ vfs_check_frozen(s, SB_FREEZE_WRITE);
+ put_super(s);
+ }
+}
+EXPORT_SYMBOL(get_super_thawed);
+
+/**
* get_active_super - get an active reference to the superblock of a device
* @bdev: device to get the superblock for
*
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 386da09f229..69cd5bb640f 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2496,6 +2496,7 @@ extern void get_filesystem(struct file_system_type *fs);
extern void put_filesystem(struct file_system_type *fs);
extern struct file_system_type *get_fs_type(const char *name);
extern struct super_block *get_super(struct block_device *);
+extern struct super_block *get_super_thawed(struct block_device *);
extern struct super_block *get_active_super(struct block_device *bdev);
extern void drop_super(struct super_block *sb);
extern void iterate_supers(void (*)(struct super_block *, void *), void *);