linux-kernel - Re: [PATCH 02/22] r/o bind mounts: add vfsmount writer counts

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Date:	Sat, 10 Feb 2007 00:41:16 +0100
From:	Eric Dumazet <dada1@...mosbay.com>
To:	Dave Hansen <hansendc@...ibm.com>
CC:	linux-kernel@...r.kernel.org, akpm@...l.org, hch@...radead.org
Subject: Re: [PATCH 02/22] r/o bind mounts: add vfsmount writer counts

Dave Hansen a écrit :

> @@ -56,6 +57,7 @@ struct vfsmount {
>  	struct vfsmount *mnt_master;	/* slave is on master->mnt_slave_list */
>  	struct mnt_namespace *mnt_ns;	/* containing namespace */
>  	struct user_namespace *mnt_user_ns; /* namespace for uid interpretation */
> +	int mnt_writers;		/* nr files open for write */
>  	/*
>  	 * We put mnt_count & mnt_expiry_mark at the end of struct vfsmount
>  	 * to let these frequently modified fields in a separate cache line
> @@ -72,7 +74,26 @@ static inline struct vfsmount *mntget(st
>  		atomic_inc(&mnt->mnt_count);
>  	return mnt;

Dave, please read again this comment in struct vfsmount definition.

If I understand your infrastructure, mnt_writers is going to be frequently 
modified, so it should be placed at the end of struct vfsmount, in the same 
cache line than mnt_count.

Thank you
Eric

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