dm: remove unused functions (fwd)

The patch forwarded below still applies and compiles against 2.6.10-rc2-mm3.

Please apply or comment on it.

----- Forwarded message from Adrian Bunk <[email protected]> -----

Date: Fri, 29 Oct 2004 02:15:49 +0200
From: Adrian Bunk <[email protected]>
To: [email protected]
Cc: [email protected]
Subject: [2.6 patch] dm: remove unused functions

[ this time without the problems due to a digital signature... ]

The patch below removes two unsed functions from dm code.

diffstat output:

 drivers/md/dm-io.c   |   16 ----------------
 drivers/md/dm-snap.c |    5 -----
 2 files changed, 21 deletions(-)

@@ -149,22 +149,6 @@
 	return 0;
 }
 
-static inline void bs_bio_init(struct bio *bio)
-{
-	bio->bi_next = NULL;
-	bio->bi_flags = 1 << BIO_UPTODATE;
-	bio->bi_rw = 0;
-	bio->bi_vcnt = 0;
-	bio->bi_idx = 0;
-	bio->bi_phys_segments = 0;
-	bio->bi_hw_segments = 0;
-	bio->bi_size = 0;
-	bio->bi_max_vecs = 0;
-	bio->bi_end_io = NULL;
-	atomic_set(&bio->bi_cnt, 1);
-	bio->bi_private = NULL;
-}
-
 static unsigned _bio_count = 0;
 struct bio *bio_set_alloc(struct bio_set *bs, int gfp_mask, int nr_iovecs)
 {

@@ -271,11 +271,6 @@
 	return e;
 }
 
-static inline void free_exception(struct exception *e)
-{
-	kmem_cache_free(exception_cache, e);
-}
-
 static inline struct pending_exception *alloc_pending_exception(void)
 {
 	return mempool_alloc(pending_pool, GFP_NOIO);

-
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----- End forwarded message -----

Please check *why* the functions aren't used first.

e.g. An alloc function with a corresponding free that never gets called suggests a leak to me...

Alasdair

[email protected]

I have to admit that I don't thoroughly check the code where I find unused code. That's why I asked for comments on this patch. Ususally the maintainers of the code in question know best whether such a patch is correct or not.

Simply consider my patches as some kind of "list of unused functions".

cu
Adrian

       "Is there not promise of rain?" Ling Tan asked suddenly out
        of the darkness. There had been need of rain for many days.
       "Only a promise," Lao Er said.
                                       Pearl S. Buck - Dragon Seed

That one isn't a leak (referring to "kmem_cache_t *exception_cache" in dm-snap.c). Items are allocated from this cache using alloc_exception(). This can happen either when an existing snapshot is activated and it's exception table is read from disk into an in-memory hash-table, or when a copy-on-write completes and a new exception is added to this hash-table. As long as the snapshot is active, this hash-table remains in memory and items cannot be removed from it. When the snapshot is deactivated, we call exit_exception_table() and pass it a pointer to this hash-table and exception_cache. This routine calls kmem_cache_free() directly instead of using the free_exception() routine. The reason it doesn't use free_exception() is that exit_exception_table() is used to tear down two different but somewhat similar hash-tables, each of which uses a different kmem_cache_t.

So, it may be nice to keep the symmetric routines defined (alloc_exception() and free_exception()), but Adrian is correct in that the later is not being used, and it really can't be used without some more significant code changes.

As for bs_bio_init(), it can be safely removed. It was just a duplicate of bio_init() from fs/bio.c. The use of that call in dm-io.c was changed to use bio_init(), but apparently the routine itself was never removed.

Kevin Corry
[email protected]
http://evms.sourceforge.net/