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Commit 939b3f0b authored by Robert Jennings's avatar Robert Jennings Committed by Greg Kroah-Hartman
Browse files

zram/xvmalloc: combine duplicate block delete code 



This patch eliminates duplicate code.  The remove_block_head function
is a special case of remove_block which can be contained in remove_block
without confusion.

The portion of code in remove_block_head which was noted as "DEBUG ONLY"
is now mandatory.  Doing this provides consistent management of the double
linked list of blocks under a freelist and makes this consolidation
of delete block code safe.  The first and last blocks will have NULL
pointers in their previous and next page pointers respectively.

Additionally, any time a block is removed from a free list the next and
previous pointers will be set to NULL to avoid misuse outside xvmalloc.

Signed-off-by: default avatarRobert Jennings <rcj@linux.vnet.ibm.com>
Reviewed-by: default avatarPekka Enberg <penberg@kernel.org>
Acked-by: default avatarNitin Gupta <ngupta@vflare.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 2787f959

drivers/staging/zram/xvmalloc.c

+31 −42
Original line number Diff line number Diff line
@@ -212,55 +212,15 @@ static void insert_block(struct xv_pool *pool, struct page *page, u32 offset, 
	__set_bit(flindex, &pool->flbitmap);

}



/*

 * Remove block from head of freelist. Index 'slindex' identifies the freelist.

 */

static void remove_block_head(struct xv_pool *pool,

			struct block_header *block, u32 slindex)

{

	struct block_header *tmpblock;

	u32 flindex = slindex / BITS_PER_LONG;



	pool->freelist[slindex].page = block->link.next_page;

	pool->freelist[slindex].offset = block->link.next_offset;

	block->link.prev_page = NULL;

	block->link.prev_offset = 0;



	if (!pool->freelist[slindex].page) {

		__clear_bit(slindex % BITS_PER_LONG, &pool->slbitmap[flindex]);

		if (!pool->slbitmap[flindex])

			__clear_bit(flindex, &pool->flbitmap);

	} else {

		/*

		 * DEBUG ONLY: We need not reinitialize freelist head previous

		 * pointer to 0 - we never depend on its value. But just for

		 * sanity, lets do it.

		 */

		tmpblock = get_ptr_atomic(pool->freelist[slindex].page,

				pool->freelist[slindex].offset, KM_USER1);

		tmpblock->link.prev_page = NULL;

		tmpblock->link.prev_offset = 0;

		put_ptr_atomic(tmpblock, KM_USER1);

	}

}



/*

 * Remove block from freelist. Index 'slindex' identifies the freelist.

 */

static void remove_block(struct xv_pool *pool, struct page *page, u32 offset,

			struct block_header *block, u32 slindex)

{

	u32 flindex;

	u32 flindex = slindex / BITS_PER_LONG;

	struct block_header *tmpblock;



	if (pool->freelist[slindex].page == page

	   && pool->freelist[slindex].offset == offset) {

		remove_block_head(pool, block, slindex);

		return;

	}



	flindex = slindex / BITS_PER_LONG;



	if (block->link.prev_page) {

		tmpblock = get_ptr_atomic(block->link.prev_page,

				block->link.prev_offset, KM_USER1);
@@ -276,6 +236,35 @@ static void remove_block(struct xv_pool *pool, struct page *page, u32 offset, 
		tmpblock->link.prev_offset = block->link.prev_offset;

		put_ptr_atomic(tmpblock, KM_USER1);

	}



	/* Is this block is at the head of the freelist? */

	if (pool->freelist[slindex].page == page

	   && pool->freelist[slindex].offset == offset) {



		pool->freelist[slindex].page = block->link.next_page;

		pool->freelist[slindex].offset = block->link.next_offset;



		if (pool->freelist[slindex].page) {

			struct block_header *tmpblock;

			tmpblock = get_ptr_atomic(pool->freelist[slindex].page,

					pool->freelist[slindex].offset,

					KM_USER1);

			tmpblock->link.prev_page = NULL;

			tmpblock->link.prev_offset = 0;

			put_ptr_atomic(tmpblock, KM_USER1);

		} else {

			/* This freelist bucket is empty */

			__clear_bit(slindex % BITS_PER_LONG,

				    &pool->slbitmap[flindex]);

			if (!pool->slbitmap[flindex])

				__clear_bit(flindex, &pool->flbitmap);

		}

	}



	block->link.prev_page = NULL;

	block->link.prev_offset = 0;

	block->link.next_page = NULL;

	block->link.next_offset = 0;

}



/*
@@ -384,7 +373,7 @@ int xv_malloc(struct xv_pool *pool, u32 size, struct page **page, 


	block = get_ptr_atomic(*page, *offset, KM_USER0);



	remove_block_head(pool, block, index);

	remove_block(pool, *page, *offset, block, index);



	/* Split the block if required */

	tmpoffset = *offset + size + XV_ALIGN;