On Tue, Feb 07, 2012 at 11:37:46PM +0100, Jan Kara wrote:
> 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.
>
> Signed-off-by: Jan Kara <jack@xxxxxxx>
> ---
> fs/super.c | 47 +++++++++++++++++++++++++++++++++++------------
> include/linux/fs.h | 1 +
> 2 files changed, 36 insertions(+), 12 deletions(-)
>
> diff --git a/fs/super.c b/fs/super.c
> index 6015c02..e320239 100644
> --- a/fs/super.c
> +++ b/fs/super.c
> @@ -593,15 +593,7 @@ void iterate_supers_type(struct file_system_type *type,
>
> EXPORT_SYMBOL(iterate_supers_type);
>
> -/**
> - * get_super - get 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. %NULL is returned if no match is found.
> - */
> -
> -struct super_block *get_super(struct block_device *bdev)
> +static struct super_block *__get_super(struct block_device *bdev, bool thawed)
> {
> struct super_block *sb;
>
> @@ -618,9 +610,13 @@ rescan:
> spin_unlock(&sb_lock);
> down_read(&sb->s_umount);
> /* still alive? */
> - if (sb->s_root && (sb->s_flags & MS_BORN))
> - return sb;
> - up_read(&sb->s_umount);
> + if (sb->s_root && (sb->s_flags & MS_BORN)) {
> + if (sb->s_frozen == SB_UNFROZEN)
> + return sb;
> + up_read(&sb->s_umount);
> + vfs_check_frozen(sb, SB_FREEZE_WRITE);
> + } else
> + up_read(&sb->s_umount);
> /* nope, got unmounted */
> spin_lock(&sb_lock);
> __put_super(sb);
> @@ -631,9 +627,36 @@ rescan:
> return NULL;
> }
The thawed parameter appears to be unused and the waiting for frozen
filesystems appears to happen for all callers. Is this intentional?
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
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