linux-kernel - Re: [PATCH v2 6/7] VFS: Document s_frozen state through freeze

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Message-ID: <20120106003604.GD3790@quack.suse.cz>
Date:	Fri, 6 Jan 2012 01:36:04 +0100
From:	Jan Kara <jack@...e.cz>
To:	Kamal Mostafa <kamal@...onical.com>
Cc:	Jan Kara <jack@...e.cz>, Alexander Viro <viro@...iv.linux.org.uk>,
	Andreas Dilger <adilger.kernel@...ger.ca>,
	Matthew Wilcox <matthew@....cx>,
	Randy Dunlap <rdunlap@...otime.net>,
	Theodore Tso <tytso@....edu>, linux-doc@...r.kernel.org,
	linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, Surbhi Palande <csurbhi@...il.com>,
	Valerie Aurora <val@...consulting.com>,
	Christopher Chaltain <christopher.chaltain@...onical.com>,
	"Peter M. Petrakis" <peter.petrakis@...onical.com>,
	Mikulas Patocka <mpatocka@...hat.com>
Subject: Re: [PATCH v2 6/7] VFS: Document s_frozen state through
 freeze_super

On Thu 08-12-11 10:04:36, Kamal Mostafa wrote:
> From: Valerie Aurora <val@...consulting.com>
  Looks good. You can add:
Acked-by: Jan Kara <jack@...e.cz>

								Honza

> BugLink: https://bugs.launchpad.net/bugs/897421
> Signed-off-by: Valerie Aurora <val@...consulting.com>
> Cc: Kamal Mostafa <kamal@...onical.com>
> Tested-by: Peter M. Petrakis <peter.petrakis@...onical.com>
> [kamal@...onical.com: patch restructure]
> Signed-off-by: Kamal Mostafa <kamal@...onical.com>
> ---
>  fs/super.c |   18 ++++++++++++++++++
>  1 files changed, 18 insertions(+), 0 deletions(-)
> 
> diff --git a/fs/super.c b/fs/super.c
> index 5629d06..a56696b 100644
> --- a/fs/super.c
> +++ b/fs/super.c
> @@ -1140,6 +1140,24 @@ out:
>   * Syncs the super to make sure the filesystem is consistent and calls the fs's
>   * freeze_fs.  Subsequent calls to this without first thawing the fs will return
>   * -EBUSY.
> + *
> + * During this function, sb->s_frozen goes through these values:
> + *
> + * SB_UNFROZEN: File system is normal, all writes progress as usual.
> + *
> + * SB_FREEZE_WRITE: The file system is in the process of being frozen
> + * and any remaining out-standing writes are being synced.  Writes
> + * that complete in-process writes should be permitted but new ones
> + * should be blocked.
> + *
> + * SB_FREEZE_TRANS: The file system is frozen.  The ->freeze_fs and
> + * ->unfreeze_fs ops are the only operations permitted to write to the
> + * file system in this state.
> + *
> + * sb->s_frozen is protected by sb->s_umount.  Additionally,
> + * SB_FREEZE_WRITE is only temporarily set during freeze/thaw while
> + * holding sb->s_umount for writing, so any other callers holding
> + * sb->s_umount will never see this state.
>   */
>  int freeze_super(struct super_block *sb)
>  {
> -- 
> 1.7.5.4
> 
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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