From: Christoph Hellwig <hch@infradead.org>
To: Jan Kara <jack@suse.cz>
Cc: Ben Myers <bpm@sgi.com>, Alex Elder <elder@kernel.org>,
David Chinner <dchinner@redhat.com>,
xfs@oss.sgi.com
Subject: Re: [PATCH v2] xfs: Fix overallocation in xfs_buf_allocate_memory()
Date: Wed, 20 Jun 2012 02:39:01 -0400 [thread overview]
Message-ID: <20120620063901.GA14760@infradead.org> (raw)
In-Reply-To: <1338935546-3914-1-git-send-email-jack@suse.cz>
On Wed, Jun 06, 2012 at 12:32:26AM +0200, Jan Kara wrote:
> Commit de1cbee which removed b_file_offset in favor of b_bn introduced a bug
> causing xfs_buf_allocate_memory() to overestimate the number of necessary
> pages. The problem is that xfs_buf_alloc() sets b_bn to -1 and thus effectively
> every buffer is straddling a page boundary which causes
> xfs_buf_allocate_memory() to allocate two pages and use vmalloc() for access
> which is unnecessary.
>
> Dave says xfs_buf_alloc() doesn't need to set b_bn to -1 anymore since the
> buffer is inserted into the cache only after being fully initialized now.
> So just make xfs_buf_alloc() fill in proper block number from the beginning.
Looks good. The b_io_length initialization in xfs_buf_get can also be
removed, but as that's a cosmetic change it can way for 3.6.
Reviewed-by: Christoph Hellwig <hch@lst.de>
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next prev parent reply other threads:[~2012-06-20 6:39 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-05 22:32 [PATCH v2] xfs: Fix overallocation in xfs_buf_allocate_memory() Jan Kara
2012-06-20 6:39 ` Christoph Hellwig [this message]
2012-06-20 6:41 ` Dave Chinner
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