linux-kernel - [PATCH 3/7] [v2] zram/xvmalloc: free bit block insertion optimization

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Message-ID: <20110128145853.GD2062@linux.vnet.ibm.com>
Date:	Fri, 28 Jan 2011 08:58:54 -0600
From:	Robert Jennings <rcj@...ux.vnet.ibm.com>
To:	Nitin Gupta <ngupta@...are.org>
Cc:	Greg Kroah-Hartman <gregkh@...e.de>,
	Robert Jennings <rcj@...ux.vnet.ibm.com>,
	Pekka Enberg <penberg@...helsinki.fi>,
	devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: [PATCH 3/7] [v2] zram/xvmalloc: free bit block insertion
 optimization

This change is in a conditional block which is entered only when there is
an existing data block on the freelist where the insert has taken place.

The new block is pushed onto the freelist stack and this conditional block
is updating links in the prior stack head to point to the new stack head.
After this conditional block the first-/second-level indices are updated
to indicate that there is a free block at this location.

This patch adds an immediate return from the conditional block to avoid
setting bits again to indicate a free block on this freelist. The bits
would already be set because there was an existing free block on this
freelist.

Signed-off-by: Robert Jennings <rcj@...ux.vnet.ibm.com>
---
 drivers/staging/zram/xvmalloc.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/drivers/staging/zram/xvmalloc.c b/drivers/staging/zram/xvmalloc.c
index b644067..149138a 100644
--- a/drivers/staging/zram/xvmalloc.c
+++ b/drivers/staging/zram/xvmalloc.c
@@ -200,6 +200,8 @@ static void insert_block(struct xv_pool *pool, struct page *page, u32 offset,
 		nextblock->link.prev_page = page;
 		nextblock->link.prev_offset = offset;
 		put_ptr_atomic(nextblock, KM_USER1);
+		/* If there was a next page then the free bits are set. */
+		return;
 	}

 	__set_bit(slindex % BITS_PER_LONG, &pool->slbitmap[flindex]);
-- 
1.7.0.4

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