From: Christoph Hellwig <hch@lst.de>
To: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: linux-xfs@vger.kernel.org, hch@lst.de, chandanrlinux@gmail.com
Subject: Re: [PATCH 2/2] xfs: fix deadlock and streamline xfs_getfsmap performance
Date: Tue, 6 Oct 2020 08:26:26 +0200 [thread overview]
Message-ID: <20201006062626.GC7033@lst.de> (raw)
In-Reply-To: <160192209677.2569942.16673759463630442919.stgit@magnolia>
On Mon, Oct 05, 2020 at 11:21:36AM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
>
> Refactor xfs_getfsmap to improve its performance: instead of indirectly
> calling a function that copies one record to userspace at a time, create
> a shadow buffer in the kernel and copy the whole array once at the end.
> On the author's computer, this reduces the runtime on his /home by ~20%.
>
> This also eliminates a deadlock when running GETFSMAP against the
> realtime device. The current code locks the rtbitmap to create
> fsmappings and copies them into userspace, having not released the
> rtbitmap lock. If the userspace buffer is an mmap of a sparse file that
> itself resides on the realtime device, the write page fault will recurse
> into the fs for allocation, which will deadlock on the rtbitmap lock.
>
> Fixes: 4c934c7dd60c ("xfs: report realtime space information via the rtbitmap")
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Looks good,
Reviewed-by: Christoph Hellwig <hch@lst.de>
next prev parent reply other threads:[~2020-10-06 6:26 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-05 18:21 [PATCH v2 0/2] xfs: a few fixes and cleanups to GETFSMAP Darrick J. Wong
2020-10-05 18:21 ` [PATCH 1/2] xfs: limit entries returned when counting fsmap records Darrick J. Wong
2020-10-05 18:21 ` [PATCH 2/2] xfs: fix deadlock and streamline xfs_getfsmap performance Darrick J. Wong
2020-10-06 6:26 ` Christoph Hellwig [this message]
2020-10-07 8:40 ` Chandan Babu R
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