xfs: remove pointless pointer increment in xfs_dir2_block_compact()

PATCH In review Eric Sandeen 2 participants 3 messages Apr 9, 2014 XFS filesystem

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Eric Sandeen

author

2014-04-09 20:30 UTC #0 lore raw

PATCH 1/1 xfs: remove pointless pointer increment in xfs_dir2_block_compact()

xfs_dir2_block_compact() is passed a pointer to *blp, and advances it locally - but nobody uses the pointer (locally) after that.

This behavior came about as part of prior refactoring,

20f7e9f xfs: factor dir2 block read operations

and looking at the code as it was before, it seems quite clear that this change introduced a bug; the pre-refactoring code expects blp to be modified after compaction.
And indeed it did; see this commit which fixed it:

37f1356 xfs: recalculate leaf entry pointer after compacting a dir2 block

So the bug was introduced & resolved in the 3.8 cycle.

Whoops. Well, it's fixed now, and mystery solved; just remove the now-pointless local increment of the blp pointer.

(I guess we should have run clang earlier!)

Signed-off-by Eric Sandeen <[email protected]>

---

fs/xfs/xfs_dir2_block.c +0 -1

index 4f6a38c..5259939 100644
@@ -319,7 +319,6 @@ xfs_dir2_block_compact(
 		(xfs_dir2_data_aoff_t)((char *)blp - (char *)hdr),
 		(xfs_dir2_data_aoff_t)((be32_to_cpu(btp->stale) - 1) * sizeof(*blp)),
 		needlog, &needscan);
-	blp += be32_to_cpu(btp->stale) - 1;
 	btp->stale = cpu_to_be32(1);
 	/*
 	 * If we now need to rebuild the bestfree map, do so.

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Mark Tinguely

Reviewed-by on v1 1/1

2014-04-09 21:34 UTC #1 lore raw

Quoted 17 lines · Eric Sandeen

xfs_dir2_block_compact() is passed a pointer to *blp, and advances it locally - but nobody uses the pointer (locally) after that.
This behavior came about as part of prior refactoring,
20f7e9f xfs: factor dir2 block read operations
and looking at the code as it was before, it seems quite clear that this change introduced a bug; the pre-refactoring code expects blp to be modified after compaction.
And indeed it did; see this commit which fixed it:
37f1356 xfs: recalculate leaf entry pointer after compacting a dir2 block
So the bug was introduced & resolved in the 3.8 cycle.

Quoted 7 lines

Whoops. Well, it's fixed now, and mystery solved; just remove the now-pointless local increment of the blp pointer.
(I guess we should have run clang earlier!)
Signed-off-by Eric Sandeen<[email protected]>
---

Harmless, but yes it should be removed.

Reviewed-by Mark Tinguely <[email protected]>

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Eric Sandeen

author

2014-04-09 21:35 UTC #2 lore raw

Quoted 21 lines · Mark Tinguely

Quoted 20 lines · Eric Sandeen
xfs_dir2_block_compact() is passed a pointer to *blp, and advances it locally - but nobody uses the pointer (locally) after that.
This behavior came about as part of prior refactoring,
20f7e9f xfs: factor dir2 block read operations
and looking at the code as it was before, it seems quite clear that this change introduced a bug; the pre-refactoring code expects blp to be modified after compaction.
And indeed it did; see this commit which fixed it:
37f1356 xfs: recalculate leaf entry pointer after compacting a dir2 block
So the bug was introduced & resolved in the 3.8 cycle.
Whoops. Well, it's fixed now, and mystery solved; just remove the now-pointless local increment of the blp pointer.

Quoted 6 lines

Quoted 4 lines
(I guess we should have run clang earlier!)
Signed-off-by Eric Sandeen<[email protected]>
---
Harmless, but yes it should be removed.

Harmless now that we fixed it the hard way back in January... ;)

thanks for the reviews,
-Eric

Quoted 1 line

Reviewed-by Mark Tinguely <[email protected]>

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