[v6,2/7] btrfs: don't kmap() pages from block devices
diff mbox series

Message ID 20200210183225.10137-3-johannes.thumshirn@wdc.com
State New
Headers show
Series
  • btrfs: remove buffer heads form superblock handling
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Commit Message

Johannes Thumshirn Feb. 10, 2020, 6:32 p.m. UTC
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>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
---
 fs/btrfs/volumes.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

Patch
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diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 6ebdd95b798d..620794f1ea64 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);