linux-kernel - [PATCH 4/4] fs/btrfs: Convert block context kmap's to kmap_local

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Date:   Tue, 16 Feb 2021 18:48:26 -0800
From:   ira.weiny@...el.com
To:     David Sterba <dsterba@...e.cz>
Cc:     Ira Weiny <ira.weiny@...el.com>, Chris Mason <clm@...com>,
        Josef Bacik <josef@...icpanda.com>,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: [PATCH 4/4] fs/btrfs: Convert block context kmap's to kmap_local_page()

From: Ira Weiny <ira.weiny@...el.com>

btrfsic_read_block() (which calls kmap()) and
btrfsic_release_block_ctx() (which calls kunmap()) are always called
within a single thread of execution.

Therefore the mappings created within these calls can be a thread local
mapping.

Convert the kmap() of bloc_ctx->pagev to kmap_local_page().  Luckily the
unmap loops backwards through the array pointer so no adjustment needs
to be made to the unmapping order.

Signed-off-by: Ira Weiny <ira.weiny@...el.com>
---
 fs/btrfs/check-integrity.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/check-integrity.c b/fs/btrfs/check-integrity.c
index 726eb894be8b..1ff9e19508a7 100644
--- a/fs/btrfs/check-integrity.c
+++ b/fs/btrfs/check-integrity.c
@@ -1558,7 +1558,7 @@ static void btrfsic_release_block_ctx(struct btrfsic_block_data_ctx *block_ctx)
 		while (num_pages > 0) {
 			num_pages--;
 			if (block_ctx->datav[num_pages]) {
-				kunmap(block_ctx->pagev[num_pages]);
+				kunmap_local(block_ctx->datav[num_pages]);
 				block_ctx->datav[num_pages] = NULL;
 			}
 			if (block_ctx->pagev[num_pages]) {
@@ -1637,7 +1637,7 @@ static int btrfsic_read_block(struct btrfsic_state *state,
 		i = j;
 	}
 	for (i = 0; i < num_pages; i++)
-		block_ctx->datav[i] = kmap(block_ctx->pagev[i]);
+		block_ctx->datav[i] = kmap_local_page(block_ctx->pagev[i]);
 
 	return block_ctx->len;
 }
-- 
2.28.0.rc0.12.gb6a658bd00c9