From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Chinner Subject: Re: [PATCH 1/2] vfs: Provide function to get superblock and wait for it to thaw Date: Thu, 9 Feb 2012 10:20:49 +1100 Message-ID: <20120208232049.GC7479@dastard> References: <1328654267-18855-1-git-send-email-jack@suse.cz> <1328654267-18855-2-git-send-email-jack@suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Al Viro , linux-fsdevel@vger.kernel.org, LKML , mpatocka@redhat.com, sandeen@sandeen.net To: Jan Kara Return-path: Content-Disposition: inline In-Reply-To: <1328654267-18855-2-git-send-email-jack@suse.cz> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org 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 > --- > 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@fromorbit.com