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Re: [PATCH 07/17] vfs: Introduce new helpers for syncing after writing t

To: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Subject: Re: [PATCH 07/17] vfs: Introduce new helpers for syncing after writing to O_SYNC file or IS_SYNC inode
From: Jamie Lokier <jamie@xxxxxxxxxxxxx>
Date: Sun, 30 Aug 2009 17:35:51 +0100
Cc: Jan Kara <jack@xxxxxxx>, LKML <linux-kernel@xxxxxxxxxxxxxxx>, hch@xxxxxx, linux-fsdevel@xxxxxxxxxxxxxxx, Evgeniy Polyakov <zbr@xxxxxxxxxxx>, ocfs2-devel@xxxxxxxxxxxxxx, Joel Becker <joel.becker@xxxxxxxxxx>, Felix Blyakher <felixb@xxxxxxx>, xfs@xxxxxxxxxxx, Anton Altaparmakov <aia21@xxxxxxxxxx>, linux-ntfs-dev@xxxxxxxxxxxxxxxxxxxxx, OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>, linux-ext4@xxxxxxxxxxxxxxx, tytso@xxxxxxx
In-reply-to: <20090827173540.GA19115@xxxxxxxxxxxxx>
References: <1250875447-15622-1-git-send-email-jack@xxxxxxx> <1250875447-15622-8-git-send-email-jack@xxxxxxx> <20090827173540.GA19115@xxxxxxxxxxxxx>
User-agent: Mutt/1.5.13 (2006-08-11)
Christoph Hellwig wrote:
> int generic_write_sync(struct file *file, loff_t pos, loff_t count)
> {
>       if (!(file->f_flags & O_SYNC) && !IS_SYNC(file->f_mapping->host))
>               return 0;
>       return vfs_fsync_range(file, file->f_path.dentry, pos,
>                              pos + count - 1, 1);
> }
> 
> and we can look into replacing the datasync flag with something more
> meaningfull later through the whole fsync stack.

I like that.  It looks really clear and self-documenting, if
vfs_fsync_range does what it sounds like, which is a nice change.

If I've guessed right what that code does, proper O_RSYNC will be easy:

int generic_sync_before_read(struct file *file, loff_t pos, loff_t count)
{
        int is_sync = ((file->f_flags & O_SYNC)
                       || IS_SYNC(file->f_mapping->host));
        int is_dsync = is_sync || (file->f_flags & O_DSYNC);

        if (!is_dsync || !(file->f_flags & O_RSYNC))
                return 0;
        return vfs_fsync_range(file, file->f_ath.denty, pos,
                               pos + count - 1, is_sync);
}

(By the way, did I mention Irix has range-fsync and range-fdatasync
system calls too :-) (actually fcntls))

-- Jamie

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