Subject: Re: [lkml]Re: VM problems still in 2.2.18
To: andrea@suse.de (Andrea Arcangeli)
Date: Fri, 15 Dec 2000 17:57:18 +0000 (GMT)
Cc: alan@lxorguk.ukuu.org.uk (Alan Cox), jjs@toyota.com (J Sloan),
        linux-kernel@vger.kernel.org (Linux kernel)
In-Reply-To: <20001215152908.M11505@inspiron.random> from "Andrea Arcangeli" at Dec 15, 2000 03:29:08 PM
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From: Alan Cox <alan@lxorguk.ukuu.org.uk>
Sender: linux-kernel-owner@vger.kernel.org

> The changes in semaphore semantics are necessary to fix the spurious out of
> memory with MAP_SHARED mappings and they came together with the removal of the
> always-asynchronous kpiod. While it's certainly possible to remove it I don't
> think removing the fix for MAP_SHARED stuff is a good idea.

How hard is it to seperate losing kpiod (optimisation) from the MAP_SHARED 
changes ? I am assuming they are two seperate issues, possibly wrongly

> Basically it's always safe to replace:
> 
> 	down(&inode->i_sem);
> 	/* critical section */
> 	up(&inode->isem);
> 
> with the new fs-semaphore:
> 
> 	fs_down(&inode->i_sem);
> 	/* critical section */
> 	fs_up(&inode->i_sem);

Providing no inode semaphore is upped from a different task , which seems
currently quite a valid legal thing to do (ditto doing the up on completion of
something in bh or irq context)

Alan

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