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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>
This commit is contained in:
Johannes Thumshirn 2020-02-14 00:24:30 +09:00 committed by David Sterba
parent f6d9abbc1f
commit c514c9b10b
1 changed files with 2 additions and 3 deletions
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5
fs/btrfs/volumes.c
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@ -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);