bio.c: make bio_destructor static

bio_destructor in fs/bio.c isn't used outside of this file, and after quickly thinking about it I didn't find a reason why it should.

The patch below makes it static.

@@ -91,7 +91,7 @@
 /*
  * default destructor for a bio allocated with bio_alloc()
  */
-void bio_destructor(struct bio *bio)
+static void bio_destructor(struct bio *bio)
 {
 	const int pool_idx = BIO_POOL_IDX(bio);
 	struct biovec_pool *bp = bvec_array + pool_idx;

Jens,

This change does not break me either. Seems benign. One thing to consider is the ability to remap block addresses from bios for mv operations that occur across mount points. At present, do_rename returns -EXDEV if someone attempts an mv operation accross mount points which point to physical storage in the same system, and requires all the data copy up to user space then back down. This seems wasteful of cycles and inefficient.

A better model, and one I have implemented in the dsfs file system (I changed do_rename extensively) is to cache the mv'd file and alias the bio chain to point to the new disk location during mv commands, even across mount points, and allow the data to DMA directly between local mount points without moving the data up to user space and back down.

I am doing this with some heavy modifications, but I think it more appropriately should be a kernel feature "fait acompli." The bio interface in the buffer cache (and some triggers in do rename) has to be able to remap data chains to another device on the fly.

Why? If you are using remote Fiber Channel adapters that map storage local as SCSI it's super fast and low cycle overhead to simply mv the files and have them dma out on the storage and skip the inefficient user space copy.

Just a suggestion.

Jeff