btrfs: remove unnecessary -ENOMEM BUG_ON check in extent-tree.c/exclude_super_stripes

PATCH In review Wang Sheng-Hui 2 participants 3 messages Sep 6, 2012 Btrfs file system

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Wang Sheng-Hui

author

2012-09-06 06:40 UTC #0 lore raw

PATCH 1/3 btrfs: remove unnecessary -ENOMEM BUG_ON check in extent-tree.c/exclude_super_stripes

The memory allocation failure is BUG_ON in add_excluded_extent (following the code path) and btrfs_rmap_block. No need to BUG_ON -ENOMEM inside exclude_super_stripes itself.

Its return value is always 0, and useless for its callers. Set it as void instead 0-returned.

Signed-off-by Wang Sheng-Hui <[email protected]>

---
 fs/btrfs/extent-tree.c |   20 +++++++-------------
 1 files changed, 7 insertions(+), 13 deletions(-)

fs/btrfs/extent-tree.c +7 ~~-13~~

index ba58024..95492cc 100644
@@ -234,39 +234,33 @@ static void free_excluded_extents(struct btrfs_root *root,
 			  start, end, EXTENT_UPTODATE, GFP_NOFS);
 }
 
-static int exclude_super_stripes(struct btrfs_root *root,
+static void exclude_super_stripes(struct btrfs_root *root,
 				 struct btrfs_block_group_cache *cache)
 {
 	u64 bytenr;
 	u64 *logical;
 	int stripe_len;
-	int i, nr, ret;
+	int i, nr;
 
 	if (cache->key.objectid < BTRFS_SUPER_INFO_OFFSET) {
 		stripe_len = BTRFS_SUPER_INFO_OFFSET - cache->key.objectid;
 		cache->bytes_super += stripe_len;
-		ret = add_excluded_extent(root, cache->key.objectid,
-					  stripe_len);
-		BUG_ON(ret); /* -ENOMEM */
+		add_excluded_extent(root, cache->key.objectid, stripe_len);
 	}
 
 	for (i = 0; i < BTRFS_SUPER_MIRROR_MAX; i++) {
 		bytenr = btrfs_sb_offset(i);
-		ret = btrfs_rmap_block(&root->fs_info->mapping_tree,
-				       cache->key.objectid, bytenr,
-				       0, &logical, &nr, &stripe_len);
-		BUG_ON(ret); /* -ENOMEM */
+		btrfs_rmap_block(&root->fs_info->mapping_tree,
+				 cache->key.objectid, bytenr,
+				 0, &logical, &nr, &stripe_len);
 
 		while (nr--) {
 			cache->bytes_super += stripe_len;
-			ret = add_excluded_extent(root, logical[nr],
-						  stripe_len);
-			BUG_ON(ret); /* -ENOMEM */
+			add_excluded_extent(root, logical[nr], stripe_len);
 		}
 
 		kfree(logical);
 	}
-	return 0;
 }
 
 static struct btrfs_caching_control *

Signature · 1 line

1.7.1

David Sterba

2012-09-06 10:09 UTC #1 lore raw

Quoted 3 lines · Wang Sheng-Hui

The memory allocation failure is BUG_ON in add_excluded_extent (following the code path) and btrfs_rmap_block. No need to BUG_ON -ENOMEM inside exclude_super_stripes itself.

No please.

Quoted 2 lines

Its return value is always 0, and useless for its callers. Set it as void instead 0-returned.

btrfs_rmap_block itself contains a BUG_ON:

3980 int btrfs_rmap_block(struct btrfs_mapping_tree *map_tree,
3981 u64 chunk_start, u64 physical, u64 devid,
3982 u64 **logical, int *naddrs, int *stripe_len)
3983 {

3984         struct extent_map_tree *em_tree = &map_tree->map_tree;
3985         struct extent_map *em;
3986         struct map_lookup *map;
3987         u64 *buf;
3988         u64 bytenr;
3989         u64 length;
3990         u64 stripe_nr;
3991         int i, j, nr = 0;
3992
3993         read_lock(&em_tree->lock);
3994         em = lookup_extent_mapping(em_tree, chunk_start, 1);
3995         read_unlock(&em_tree->lock);

3996
3997 BUG_ON(!em || em->start != chunk_start);

And this should be turned into an 'return error', thus giving a non-zero return code that should be handled in the callers.

Eg. this patch attempts to do that
http://www.mail-archive.com/[email protected]/msg15470.html

but has not been merged due to incorrect fix inside exclude_super_stripes (introduced in the patch).

The same objection for return code cleanups will hold for any function that returns 0 but is full of BUG_ONs.

david

Wang Sheng-Hui

author

2012-09-06 14:12 UTC #2 lore raw

Quoted 37 lines · David Sterba

Quoted 3 lines · Wang Sheng-Hui
The memory allocation failure is BUG_ON in add_excluded_extent (following the code path) and btrfs_rmap_block. No need to BUG_ON -ENOMEM inside exclude_super_stripes itself.
No please.
Quoted 2 lines
Its return value is always 0, and useless for its callers. Set it as void instead 0-returned.
btrfs_rmap_block itself contains a BUG_ON:
3980 int btrfs_rmap_block(struct btrfs_mapping_tree *map_tree,
3981 u64 chunk_start, u64 physical, u64 devid,
3982 u64 **logical, int *naddrs, int *stripe_len)
3983 {
3984         struct extent_map_tree *em_tree = &map_tree->map_tree;
3985         struct extent_map *em;
3986         struct map_lookup *map;
3987         u64 *buf;
3988         u64 bytenr;
3989         u64 length;
3990         u64 stripe_nr;
3991         int i, j, nr = 0;
3992
3993         read_lock(&em_tree->lock);
3994         em = lookup_extent_mapping(em_tree, chunk_start, 1);
3995         read_unlock(&em_tree->lock);
3996
3997 BUG_ON(!em || em->start != chunk_start);
And this should be turned into an 'return error', thus giving a non-zero return code that should be handled in the callers.
Eg. this patch attempts to do that
http://www.mail-archive.com/[email protected]/msg15470.html

Quoted 8 lines

but has not been merged due to incorrect fix inside exclude_super_stripes (introduced in the patch).
The same objection for return code cleanups will hold for any function that returns 0 but is full of BUG_ONs.
david

Got it. Thanks, David!

Regards,
Sheng-Hui