From c514c9b10bc1ec8b487e82900ab57f46a21956d9 Mon Sep 17 00:00:00 2001 From: Johannes Thumshirn 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 Reviewed-by: Christoph Hellwig Signed-off-by: Johannes Thumshirn Reviewed-by: David Sterba Signed-off-by: David Sterba --- 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 89be36a0fed6..00baa806662a 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);