[PATCH] EXT2: Remove superblock lock contention in ext2_statfs

Dave Kleikamp
2006-09-18T20:36:33Z

EXT2: Remove superblock lock contention in ext2_statfs

Fix a performance degradation introduced in 2.6.17. (30% degradation running
dbench with 16 threads)

Patch 21730eed11de42f22afcbd43f450a1872a0b5ea1, which claims to make
EXT2_DEBUG work again, moves the taking of the kernel lock out of debug-only
code in ext2_count_free_inodes and ext2_count_free_blocks and into
ext2_statfs. This patch reverses that part of the patch.

Signed-off-by: Dave Kleikamp <shaggy@austin.ibm.com>

diff --git a/fs/ext2/balloc.c b/fs/ext2/balloc.c
index d487043..fddefff 100644
--- a/fs/ext2/balloc.c
+++ b/fs/ext2/balloc.c
@@ -539,7 +539,6 @@ unsigned long ext2_count_free (struct bu

#endif /* EXT2FS_DEBUG */

-/* Superblock must be locked */
unsigned long ext2_count_free_blocks (struct super_block * sb)
{
struct ext2_group_desc * desc;
@@ -549,6 +548,7 @@ #ifdef EXT2FS_DEBUG
unsigned long bitmap_count, x;
struct ext2_super_block *es;

+ lock_super(sb);
es = EXT2_SB(sb)->s_es;
desc_count = 0;
bitmap_count = 0;
@@ -572,6 +572,7 @@ #ifdef EXT2FS_DEBUG
printk("ext2_count_free_blocks: stored = %lu, computed = %lu, %lu\n",
(long)le32_to_cpu(es->s_free_blocks_count),
desc_count, bitmap_count);
+ unlock_super(sb);
return bitmap_count;
#else
for (i = 0; i < EXT2_SB(sb)->s_groups_count; i++) {
diff --git a/fs/ext2/ialloc.c b/fs/ext2/ialloc.c
index de85c61..5d1d1c9 100644
--- a/fs/ext2/ialloc.c
+++ b/fs/ext2/ialloc.c
@@ -637,7 +637,6 @@ fail:
return ERR_PTR(err);
}

-/* Superblock must be locked */
unsigned long ext2_count_free_inodes (struct super_block * sb)
{
struct ext2_group_desc *desc;
@@ -649,6 +648,7 @@ #ifdef EXT2FS_DEBUG
unsigned long bitmap_count = 0;
struct buffer_head *bitmap_bh = NULL;

+ lock_super(sb);
es = EXT2_SB(sb)->s_es;
for (i = 0; i < EXT2_SB(sb)->s_groups_count; i++) {
unsigned x;
@@ -671,6 +671,7 @@ #ifdef EXT2FS_DEBUG
printk("ext2_count_free_inodes: stored = %lu, computed = %lu, %lu\n",
percpu_counter_read(&EXT2_SB(sb)->s_freeinodes_counter),
desc_count, bitmap_count);
+ unlock_super(sb);
return desc_count;
#else
for (i = 0; i < EXT2_SB(sb)->s_groups_count; i++) {
diff --git a/fs/ext2/super.c b/fs/ext2/super.c
index ca5bfb6..4286ff6 100644
--- a/fs/ext2/super.c
+++ b/fs/ext2/super.c
@@ -1083,7 +1083,6 @@ static int ext2_statfs (struct dentry *
unsigned long overhead;
int i;

- lock_super(sb);
if (test_opt (sb, MINIX_DF))
overhead = 0;
else {
@@ -1124,7 +1123,6 @@ static int ext2_statfs (struct dentry *
buf->f_files = le32_to_cpu(sbi->s_es->s_inodes_count);
buf->f_ffree = ext2_count_free_inodes (sb);
buf->f_namelen = EXT2_NAME_LEN;
- unlock_super(sb);
return 0;
}

--
David Kleikamp
IBM Linux Technology Center