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

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Date:   Sun, 28 Mar 2021 23:54:00 -0700
From:   ira.weiny@...el.com
To:     Jan Kara <jack@...e.com>
Cc:     Ira Weiny <ira.weiny@...el.com>, linux-ext4@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 0/2] ext2: Convert kmap to kmap_local_page

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.

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