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From: David Sterba <>
Cc: Chris Mason <>, Josef Bacik <>,,
Subject: Re: [PATCH 2/4] fs/btrfs: Convert raid5/6 kmaps to kmap_local_page()
Date: Fri, 12 Mar 2021 20:26:34 +0100	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Tue, Feb 16, 2021 at 06:48:24PM -0800, wrote:
> From: Ira Weiny <>
> These kmaps are thread local and don't need to be atomic.  So they can use
> the more efficient kmap_local_page().  However, the mapping of pages in
> the stripes and the additional parity and qstripe pages are a bit
> trickier because the unmapping must occur in the opposite order from the
> mapping.  Furthermore, the pointer array in __raid_recover_end_io() may
> get reordered.
> Convert these calls to kmap_local_page() taking care to reverse the
> unmappings of any page arrays as well as being careful with the mappings
> of any special pages such as the parity and qstripe pages.

Though there's one more allocation for the additional array, I don't see
a simpler way to avoid it and track the array reordering at a lower
memory cost. At least it's not in a performance critical code and the
array size is reasonably small.

  reply	other threads:[~2021-03-12 19:29 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-17  2:48 [PATCH 0/4] btrfs: Convert more kmaps to kmap_local_page() ira.weiny
2021-02-17  2:48 ` [PATCH 1/4] fs/btrfs: Convert kmap to kmap_local_page() using coccinelle ira.weiny
2021-03-12 18:58   ` David Sterba
2021-03-12 20:03     ` Ira Weiny
2021-03-16 11:04       ` David Sterba
2021-02-17  2:48 ` [PATCH 2/4] fs/btrfs: Convert raid5/6 kmaps to kmap_local_page() ira.weiny
2021-03-12 19:26   ` David Sterba [this message]
2021-02-17  2:48 ` [PATCH 3/4] fs/btrfs: Use kmap_local_page() in __btrfsic_submit_bio() ira.weiny
2021-02-17  2:48 ` [PATCH 4/4] fs/btrfs: Convert block context kmap's to kmap_local_page() ira.weiny
2021-03-11 21:30 ` [PATCH 0/4] btrfs: Convert more kmaps " Ira Weiny
2021-03-12 19:41 ` David Sterba
2021-03-12 20:05   ` Ira Weiny
2021-03-16 11:07     ` David Sterba
2021-03-16 16:56       ` Ira Weiny

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