From a9f06a61b2d8c31271afa2501bdf8fa06a772f8b Mon Sep 17 00:00:00 2001
From: nikita <nikita>
Date: Mon, 20 Nov 2006 23:17:56 +0000
Subject: [PATCH] __find_get_block_slow-scale.patch: attempt to reduce
 contention on bd_mapping->private_lock.

---
 .../patches/__find_get_block_slow-scale.patch      | 43 ++++++++++++++++++++++
 lustre/kernel_patches/series/2.6-rhel4.series      |  1 +
 2 files changed, 44 insertions(+)
 create mode 100644 lustre/kernel_patches/patches/__find_get_block_slow-scale.patch

diff --git a/lustre/kernel_patches/patches/__find_get_block_slow-scale.patch b/lustre/kernel_patches/patches/__find_get_block_slow-scale.patch
new file mode 100644
index 0000000..1da92d4
--- /dev/null
+++ b/lustre/kernel_patches/patches/__find_get_block_slow-scale.patch
@@ -0,0 +1,43 @@
+Index: linux/fs/buffer.c
+===================================================================
+--- linux.orig/fs/buffer.c
++++ linux/fs/buffer.c
+@@ -509,13 +509,18 @@ __find_get_block_slow(struct block_devic
+ 	struct buffer_head *head;
+ 	struct page *page;
+ 	int all_mapped = 1;
++	int spinlock = 0;
+ 
+ 	index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits);
+ 	page = find_get_page(bd_mapping, index);
+ 	if (!page)
+ 		goto out;
+ 
++	if (unlikely(TestSetPageLocked(page))) {
+ 	spin_lock(&bd_mapping->private_lock);
++		spinlock = 1;
++	}
++
+ 	if (!page_has_buffers(page))
+ 		goto out_unlock;
+ 	head = page_buffers(page);
+@@ -536,7 +541,7 @@ __find_get_block_slow(struct block_devic
+ 	 * file io on the block device and getblk.  It gets dealt with
+ 	 * elsewhere, don't buffer_error if we had some unmapped buffers
+ 	 */
+-	if (all_mapped) {
++	if (unlikely(all_mapped)) {
+ 		printk("__find_get_block_slow() failed. "
+ 			"block=%llu, b_blocknr=%llu\n",
+ 			(unsigned long long)block, (unsigned long long)bh->b_blocknr);
+@@ -544,7 +549,10 @@ __find_get_block_slow(struct block_devic
+ 		printk("device blocksize: %d\n", 1 << bd_inode->i_blkbits);
+ 	}
+ out_unlock:
++	if (unlikely(spinlock))
+ 	spin_unlock(&bd_mapping->private_lock);
++	else
++		unlock_page(page);
+ 	page_cache_release(page);
+ out:
+ 	return ret;
diff --git a/lustre/kernel_patches/series/2.6-rhel4.series b/lustre/kernel_patches/series/2.6-rhel4.series
index 2e2736e..cdd7279 100644
--- a/lustre/kernel_patches/series/2.6-rhel4.series
+++ b/lustre/kernel_patches/series/2.6-rhel4.series
@@ -35,3 +35,4 @@ dynamic-locks-2.6.9.patch
 jbd-copy-out-everything.patch 
 jbd-checkpoint-on-commit.patch 
 export-nr_free_buffer_pages.patch 
+__find_get_block_slow-scale.patch 
-- 
1.8.3.1