btrfs: make btrfs_read_disk_super return struct btrfs_disk_super

Instead of returning both the page and the super block structure, make
btrfs_read_disk_super just return a pointer to struct btrfs_disk_super.
As a result the function signature is simplified. Also,
read_cache_page_gfp can never return NULL so check its return value only
for IS_ERR.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index c1909e5f4506835f7741c5003c51ac65982a3a29..aa1e0ae32943b9b49efc966f1a006f2cc7cf25f3 100644 (file)
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1251,49 +1251,48 @@ void btrfs_release_disk_super(struct btrfs_super_block *super)
        put_page(page);
 }
 
-static int btrfs_read_disk_super(struct block_device *bdev, u64 bytenr,
-                                struct page **page,
-                                struct btrfs_super_block **disk_super)
+static struct btrfs_super_block *btrfs_read_disk_super(struct block_device *bdev,
+                                                      u64 bytenr)
 {
+       struct btrfs_super_block *disk_super;
+       struct page *page;
        void *p;
        pgoff_t index;
 
        /* make sure our super fits in the device */
        if (bytenr + PAGE_SIZE >= i_size_read(bdev->bd_inode))
-               return 1;
+               return ERR_PTR(-EINVAL);
 
        /* make sure our super fits in the page */
-       if (sizeof(**disk_super) > PAGE_SIZE)
-               return 1;
+       if (sizeof(*disk_super) > PAGE_SIZE)
+               return ERR_PTR(-EINVAL);
 
        /* make sure our super doesn't straddle pages on disk */
        index = bytenr >> PAGE_SHIFT;
-       if ((bytenr + sizeof(**disk_super) - 1) >> PAGE_SHIFT != index)
-               return 1;
+       if ((bytenr + sizeof(*disk_super) - 1) >> PAGE_SHIFT != index)
+               return ERR_PTR(-EINVAL);
 
        /* pull in the page with our super */
-       *page = read_cache_page_gfp(bdev->bd_inode->i_mapping,
-                                  index, GFP_KERNEL);
+       page = read_cache_page_gfp(bdev->bd_inode->i_mapping, index, GFP_KERNEL);
 
-       if (IS_ERR(*page))
-               return 1;
+       if (IS_ERR(page))
+               return ERR_CAST(page);
 
-       p = page_address(*page);
+       p = page_address(page);
 
        /* align our pointer to the offset of the super block */
-       *disk_super = p + offset_in_page(bytenr);
+       disk_super = p + offset_in_page(bytenr);
 
-       if (btrfs_super_bytenr(*disk_super) != bytenr ||
-           btrfs_super_magic(*disk_super) != BTRFS_MAGIC) {
+       if (btrfs_super_bytenr(disk_super) != bytenr ||
+           btrfs_super_magic(disk_super) != BTRFS_MAGIC) {
                btrfs_release_disk_super(p);
-               return 1;
+               return ERR_PTR(-EINVAL);
        }
 
-       if ((*disk_super)->label[0] &&
-               (*disk_super)->label[BTRFS_LABEL_SIZE - 1])
-               (*disk_super)->label[BTRFS_LABEL_SIZE - 1] = '\0';
+       if (disk_super->label[0] && disk_super->label[BTRFS_LABEL_SIZE - 1])
+               disk_super->label[BTRFS_LABEL_SIZE - 1] = 0;
 
-       return 0;
+       return disk_super;
 }
 
 int btrfs_forget_devices(const char *path)
@@ -1319,7 +1318,6 @@ struct btrfs_device *btrfs_scan_one_device(const char *path, fmode_t flags,
        bool new_device_added = false;
        struct btrfs_device *device = NULL;
        struct block_device *bdev;
-       struct page *page;
        u64 bytenr;
 
        lockdep_assert_held(&uuid_mutex);
@@ -1337,8 +1335,9 @@ struct btrfs_device *btrfs_scan_one_device(const char *path, fmode_t flags,
        if (IS_ERR(bdev))
                return ERR_CAST(bdev);
 
-       if (btrfs_read_disk_super(bdev, bytenr, &page, &disk_super)) {
-               device = ERR_PTR(-EINVAL);
+       disk_super = btrfs_read_disk_super(bdev, bytenr);
+       if (IS_ERR(disk_super)) {
+               device = ERR_CAST(disk_super);
                goto error_bdev_put;
        }