From c514c9b10bc1ec8b487e82900ab57f46a21956d9 Mon Sep 17 00:00:00 2001
From: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Date: Fri, 14 Feb 2020 00:24:30 +0900
Subject: [PATCH] btrfs: don't kmap() pages from block devices
Block device mappings are never in highmem so kmap() / kunmap() calls for
pages from block devices are unneeded. Use page_address() instead of
kmap() to get to the virtual addreses.
While we're at it, read_cache_page_gfp() doesn't return NULL on error,
only an ERR_PTR, so use IS_ERR() to check for errors.
Suggested-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---
fs/btrfs/volumes.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 89be36a0fed62..00baa806662a0 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1249,7 +1249,6 @@ int btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
void btrfs_release_disk_super(struct page *page)
{
- kunmap(page);
put_page(page);
}
@@ -1277,10 +1276,10 @@ static int btrfs_read_disk_super(struct block_device *bdev, u64 bytenr,
*page = read_cache_page_gfp(bdev->bd_inode->i_mapping,
index, GFP_KERNEL);
- if (IS_ERR_OR_NULL(*page))
+ if (IS_ERR(*page))
return 1;
- p = kmap(*page);
+ p = page_address(*page);
/* align our pointer to the offset of the super block */
*disk_super = p + offset_in_page(bytenr);
--
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