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Re: [PATCH] xfs: stop using the page cache to back the buffer cache

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: [PATCH] xfs: stop using the page cache to back the buffer cache
From: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Date: Fri, 11 Mar 2011 05:16:42 -0500
Cc: xfs@xxxxxxxxxxx, chris.mason@xxxxxxxxxx
In-reply-to: <1299719104-11961-1-git-send-email-david@xxxxxxxxxxxxx>
References: <1299719104-11961-1-git-send-email-david@xxxxxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
> +             if (((unsigned long)(bp->b_addr + bp->b_buffer_length - 1) &
> +                                                             PAGE_MASK) !=
> +                 ((unsigned long)bp->b_addr & PAGE_MASK)) {
> +                     /* b_addr spans two pages - use alloc_page instead */
> +                     kmem_free(bp->b_addr);
> +                     bp->b_addr = NULL;
> +                     goto use_alloc_page;
> +             }

Did you manage to hit this case?  If it happens with any frequency under
real workloads we really need to find a wayto avoid the allocation to
start with.


Otherwise looks good,

Reviewed-by: Christoph Hellwig <hch@xxxxxx>

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