linux-kernel - Re: [PATCH 0/2] ext2: Convert kmap to kmap_local

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Date:   Wed, 31 Mar 2021 14:05:08 +0200
From:   Jan Kara <jack@...e.cz>
To:     ira.weiny@...el.com
Cc:     Jan Kara <jack@...e.com>, linux-ext4@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] ext2: Convert kmap to kmap_local_page

Hi Ira!

On Sun 28-03-21 23:54:00, ira.weiny@...el.com wrote:
> From: Ira Weiny <ira.weiny@...el.com>
> 
> kmap is inefficient and can be abused so it is being phased out in favor of
> kmap_local_page where possible.
> 
> ext2 uses kmap in ext2_[get|put]_page().  All of the calls to
> ext2_[get|put]_page() occur in single threads so it is perfectly safe and
> preferable to use kmap_local_page().
> 
> This series has a clean up which matches ext2_put_page() with ext2_dotdot() and
> ext2_find_entry().  Those calls use ext2_get_page() to map the page prior to
> returning it to their callers.  And they document that ext2_put_page() should
> be matched up with them.  This was the case but the ext2_put_page() calls were
> hidden in other functions.  We lift the ext2_put_page() calls to match up to
> the functions where ext2_dotdot() and ext2_find_entry() are called.
> 
> After that clean up convert ext2_[get|put]_page() to kmap and adjust for
> kunmap_local() requiring the page address.
> 
> Nesting of kmap_local_page() calls is maintained with minor changes.

Pulled into my tree. Thanks!

								Honza

> 
> Ira Weiny (2):
>   ext2: Match up ext2_put_page() with ext2_dotdot() and
>     ext2_find_entry()
>   fs/ext2: Replace kmap() with kmap_local_page()
> 
>  fs/ext2/dir.c   | 94 +++++++++++++++++++++++++++++++------------------
>  fs/ext2/ext2.h  | 12 ++++---
>  fs/ext2/namei.c | 34 +++++++++++-------
>  3 files changed, 89 insertions(+), 51 deletions(-)
> 
> -- 
> 2.28.0.rc0.12.gb6a658bd00c9
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR