From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kara Subject: Re: [PATCH 1/2] vfs: Provide function to get superblock and wait for it to thaw Date: Thu, 9 Feb 2012 00:27:05 +0100 Message-ID: <20120208232705.GF1696@quack.suse.cz> References: <1328654267-18855-1-git-send-email-jack@suse.cz> <1328654267-18855-2-git-send-email-jack@suse.cz> <20120208232049.GC7479@dastard> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Jan Kara , Al Viro , linux-fsdevel@vger.kernel.org, LKML , mpatocka@redhat.com, sandeen@sandeen.net To: Dave Chinner Return-path: Received: from cantor2.suse.de ([195.135.220.15]:36339 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757198Ab2BHX1H (ORCPT ); Wed, 8 Feb 2012 18:27:07 -0500 Content-Disposition: inline In-Reply-To: <20120208232049.GC7479@dastard> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Thu 09-02-12 10:20:49, Dave Chinner wrote: > 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? Ah, sorry. Obviously that's a bug. Thanks for spotting it. I'll fix it up. Honza -- Jan Kara SUSE Labs, CR