Commit c514c9b1 authored Feb 14, 2020 by Johannes Thumshirn Committed by David Sterba Mar 23, 2020

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>

parent f6d9abbc

fs/btrfs/volumes.c

+2 −3

Original line number	Diff line number	Diff line
		@@ -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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