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Date: Mon, 7 Nov 2011 15:13:08 -0800
From: Vivek Haldar <haldar@...gle.com>
To: "Theodore Ts'o" <tytso@....edu>,
Andreas Dilger <adilger.kernel@...ger.ca>,
linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: Vivek Haldar <haldar@...gle.com>
Subject: [PATCH] ext4: protect extent cache with r/w spinlock.
The extent cache used to be protected by an exclusive spinlock. Using
a r/w lock instead will allow multiple concurrent readers. Also, use
percpu counters for cache hit/miss stats.
Tested: xfstests.
Signed-off-by: Vivek Haldar <haldar@...gle.com>
---
fs/ext4/ext4.h | 10 +++++++---
fs/ext4/extents.c | 17 +++++++----------
fs/ext4/super.c | 18 ++++++++++++++++--
3 files changed, 30 insertions(+), 15 deletions(-)
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 604c200..4732e55 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -882,6 +882,9 @@ struct ext4_inode_info {
ext4_io_end_t *cur_aio_dio;
atomic_t i_aiodio_unwritten; /* Nr. of inflight conversions pending */
+ /* r/w lock for extent cache */
+ rwlock_t extent_cache_lock;
+
spinlock_t i_block_reservation_lock;
/*
@@ -1183,9 +1186,10 @@ struct ext4_sb_info {
unsigned long s_ext_blocks;
unsigned long s_ext_extents;
#endif
- /* ext4 extent cache stats */
- unsigned long extent_cache_hits;
- unsigned long extent_cache_misses;
+
+ /* ext4 extent cache stats, per cpu */
+ struct percpu_counter extent_cache_hits;
+ struct percpu_counter extent_cache_misses;
/* for buddy allocator */
struct ext4_group_info ***s_group_info;
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 61fa9e1..9dd748f 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -1951,13 +1951,13 @@ ext4_ext_put_in_cache(struct inode *inode, ext4_lblk_t block,
{
struct ext4_ext_cache *cex;
BUG_ON(len == 0);
- spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
+ write_lock(&EXT4_I(inode)->extent_cache_lock);
trace_ext4_ext_put_in_cache(inode, block, len, start);
cex = &EXT4_I(inode)->i_cached_extent;
cex->ec_block = block;
cex->ec_len = len;
cex->ec_start = start;
- spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
+ write_unlock(&EXT4_I(inode)->extent_cache_lock);
}
/*
@@ -2031,10 +2031,7 @@ static int ext4_ext_check_cache(struct inode *inode, ext4_lblk_t block,
struct ext4_sb_info *sbi;
int ret = 0;
- /*
- * We borrow i_block_reservation_lock to protect i_cached_extent
- */
- spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
+ read_lock(&EXT4_I(inode)->extent_cache_lock);
cex = &EXT4_I(inode)->i_cached_extent;
sbi = EXT4_SB(inode->i_sb);
@@ -2050,12 +2047,12 @@ static int ext4_ext_check_cache(struct inode *inode, ext4_lblk_t block,
ret = 1;
}
errout:
+ trace_ext4_ext_in_cache(inode, block, ret);
+ read_unlock(&EXT4_I(inode)->extent_cache_lock);
if (!ret)
- sbi->extent_cache_misses++;
+ percpu_counter_inc(&sbi->extent_cache_misses);
else
- sbi->extent_cache_hits++;
- trace_ext4_ext_in_cache(inode, block, ret);
- spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
+ percpu_counter_inc(&sbi->extent_cache_hits);
return ret;
}
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 9953d80..739ca96 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -842,6 +842,8 @@ static void ext4_put_super(struct super_block *sb)
percpu_counter_destroy(&sbi->s_freeinodes_counter);
percpu_counter_destroy(&sbi->s_dirs_counter);
percpu_counter_destroy(&sbi->s_dirtyclusters_counter);
+ percpu_counter_destroy(&sbi->extent_cache_hits);
+ percpu_counter_destroy(&sbi->extent_cache_misses);
brelse(sbi->s_sbh);
#ifdef CONFIG_QUOTA
for (i = 0; i < MAXQUOTAS; i++)
@@ -904,6 +906,7 @@ static struct inode *ext4_alloc_inode(struct super_block *sb)
ei->i_allocated_meta_blocks = 0;
ei->i_da_metadata_calc_len = 0;
spin_lock_init(&(ei->i_block_reservation_lock));
+ rwlock_init(&(ei->extent_cache_lock));
#ifdef CONFIG_QUOTA
ei->i_reserved_quota = 0;
#endif
@@ -2507,13 +2510,15 @@ static ssize_t lifetime_write_kbytes_show(struct ext4_attr *a,
static ssize_t extent_cache_hits_show(struct ext4_attr *a,
struct ext4_sb_info *sbi, char *buf)
{
- return snprintf(buf, PAGE_SIZE, "%lu\n", sbi->extent_cache_hits);
+ return snprintf(buf, PAGE_SIZE, "%lld\n",
+ percpu_counter_sum(&sbi->extent_cache_hits));
}
static ssize_t extent_cache_misses_show(struct ext4_attr *a,
struct ext4_sb_info *sbi, char *buf)
{
- return snprintf(buf, PAGE_SIZE, "%lu\n", sbi->extent_cache_misses);
+ return snprintf(buf, PAGE_SIZE, "%lld\n",
+ percpu_counter_sum(&sbi->extent_cache_misses));
}
static ssize_t inode_readahead_blks_store(struct ext4_attr *a,
@@ -3589,6 +3594,13 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
if (!err) {
err = percpu_counter_init(&sbi->s_dirtyclusters_counter, 0);
}
+
+ /* Allocate cache hit/miss counters. */
+ if (!err)
+ err = percpu_counter_init(&sbi->extent_cache_hits, 0);
+ if (!err)
+ err = percpu_counter_init(&sbi->extent_cache_misses, 0);
+
if (err) {
ext4_msg(sb, KERN_ERR, "insufficient memory");
goto failed_mount3;
@@ -3855,6 +3867,8 @@ failed_mount3:
percpu_counter_destroy(&sbi->s_freeinodes_counter);
percpu_counter_destroy(&sbi->s_dirs_counter);
percpu_counter_destroy(&sbi->s_dirtyclusters_counter);
+ percpu_counter_destroy(&sbi->extent_cache_hits);
+ percpu_counter_destroy(&sbi->extent_cache_misses);
if (sbi->s_mmp_tsk)
kthread_stop(sbi->s_mmp_tsk);
failed_mount2:
--
1.7.3.1
--
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