[PATCH v7 3/4] dcache: replace d_lock/d_count by d_lockcnt
From: Waiman Long
Date: Mon Aug 05 2013 - 23:13:49 EST
This patch replaces the d_lock and d_count fields of the dentry
data structure by the combined d_lockcnt structure. A d_lock macro
is defined to remap the old d_lock name to the new d_lockcnt.lock
name. This is needed as a lot of files use the d_lock spinlock.
Read accesses to d_count are replaced by the d_count() helper
function. Write accesses to d_count are replaced by the new
d_lockcnt.refcnt name. Other than that, there is no other functional
change in this patch.
The offsets of the new d_lockcnt field are at byte 72 and 88 for
32-bit and 64-bit SMP systems respectively. In both cases, they are
8-byte aligned and their combination into a single 8-byte word will
not introduce a hole that increase the size of the dentry structure.
Signed-off-by: Waiman Long <Waiman.Long@xxxxxx>
---
fs/dcache.c | 54 ++++++++++++++++++++++++------------------------
fs/namei.c | 6 ++--
include/linux/dcache.h | 15 ++++++++----
3 files changed, 40 insertions(+), 35 deletions(-)
diff --git a/fs/dcache.c b/fs/dcache.c
index 87bdb53..3adb6aa 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -54,7 +54,7 @@
* - d_flags
* - d_name
* - d_lru
- * - d_count
+ * - d_lockcnt.refcnt
* - d_unhashed()
* - d_parent and d_subdirs
* - childrens' d_child and d_parent
@@ -229,7 +229,7 @@ static void __d_free(struct rcu_head *head)
*/
static void d_free(struct dentry *dentry)
{
- BUG_ON(dentry->d_count);
+ BUG_ON(d_count(dentry));
this_cpu_dec(nr_dentry);
if (dentry->d_op && dentry->d_op->d_release)
dentry->d_op->d_release(dentry);
@@ -467,7 +467,7 @@ relock:
}
if (ref)
- dentry->d_count--;
+ dentry->d_lockcnt.refcnt--;
/*
* inform the fs via d_prune that this dentry is about to be
* unhashed and destroyed.
@@ -513,12 +513,12 @@ void dput(struct dentry *dentry)
return;
repeat:
- if (dentry->d_count == 1)
+ if (d_count(dentry) == 1)
might_sleep();
spin_lock(&dentry->d_lock);
- BUG_ON(!dentry->d_count);
- if (dentry->d_count > 1) {
- dentry->d_count--;
+ BUG_ON(!d_count(dentry));
+ if (d_count(dentry) > 1) {
+ dentry->d_lockcnt.refcnt--;
spin_unlock(&dentry->d_lock);
return;
}
@@ -535,7 +535,7 @@ repeat:
dentry->d_flags |= DCACHE_REFERENCED;
dentry_lru_add(dentry);
- dentry->d_count--;
+ dentry->d_lockcnt.refcnt--;
spin_unlock(&dentry->d_lock);
return;
@@ -590,7 +590,7 @@ int d_invalidate(struct dentry * dentry)
* We also need to leave mountpoints alone,
* directory or not.
*/
- if (dentry->d_count > 1 && dentry->d_inode) {
+ if (d_count(dentry) > 1 && dentry->d_inode) {
if (S_ISDIR(dentry->d_inode->i_mode) || d_mountpoint(dentry)) {
spin_unlock(&dentry->d_lock);
return -EBUSY;
@@ -606,7 +606,7 @@ EXPORT_SYMBOL(d_invalidate);
/* This must be called with d_lock held */
static inline void __dget_dlock(struct dentry *dentry)
{
- dentry->d_count++;
+ dentry->d_lockcnt.refcnt++;
}
static inline void __dget(struct dentry *dentry)
@@ -634,8 +634,8 @@ repeat:
goto repeat;
}
rcu_read_unlock();
- BUG_ON(!ret->d_count);
- ret->d_count++;
+ BUG_ON(!d_count(ret));
+ ret->d_lockcnt.refcnt++;
spin_unlock(&ret->d_lock);
return ret;
}
@@ -718,7 +718,7 @@ restart:
spin_lock(&inode->i_lock);
hlist_for_each_entry(dentry, &inode->i_dentry, d_alias) {
spin_lock(&dentry->d_lock);
- if (!dentry->d_count) {
+ if (!d_count(dentry)) {
__dget_dlock(dentry);
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
@@ -734,7 +734,7 @@ EXPORT_SYMBOL(d_prune_aliases);
/*
* Try to throw away a dentry - free the inode, dput the parent.
- * Requires dentry->d_lock is held, and dentry->d_count == 0.
+ * Requires dentry->d_lock is held, and dentry->d_lockcnt.refcnt == 0.
* Releases dentry->d_lock.
*
* This may fail if locks cannot be acquired no problem, just try again.
@@ -764,8 +764,8 @@ static void try_prune_one_dentry(struct dentry *dentry)
dentry = parent;
while (dentry) {
spin_lock(&dentry->d_lock);
- if (dentry->d_count > 1) {
- dentry->d_count--;
+ if (d_count(dentry) > 1) {
+ dentry->d_lockcnt.refcnt--;
spin_unlock(&dentry->d_lock);
return;
}
@@ -793,7 +793,7 @@ static void shrink_dentry_list(struct list_head *list)
* the LRU because of laziness during lookup. Do not free
* it - just keep it off the LRU list.
*/
- if (dentry->d_count) {
+ if (d_count(dentry)) {
dentry_lru_del(dentry);
spin_unlock(&dentry->d_lock);
continue;
@@ -913,7 +913,7 @@ static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
dentry_lru_del(dentry);
__d_shrink(dentry);
- if (dentry->d_count != 0) {
+ if (d_count(dentry) != 0) {
printk(KERN_ERR
"BUG: Dentry %p{i=%lx,n=%s}"
" still in use (%d)"
@@ -922,7 +922,7 @@ static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
dentry->d_inode ?
dentry->d_inode->i_ino : 0UL,
dentry->d_name.name,
- dentry->d_count,
+ d_count(dentry),
dentry->d_sb->s_type->name,
dentry->d_sb->s_id);
BUG();
@@ -933,7 +933,7 @@ static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
list_del(&dentry->d_u.d_child);
} else {
parent = dentry->d_parent;
- parent->d_count--;
+ parent->d_lockcnt.refcnt--;
list_del(&dentry->d_u.d_child);
}
@@ -981,7 +981,7 @@ void shrink_dcache_for_umount(struct super_block *sb)
dentry = sb->s_root;
sb->s_root = NULL;
- dentry->d_count--;
+ dentry->d_lockcnt.refcnt--;
shrink_dcache_for_umount_subtree(dentry);
while (!hlist_bl_empty(&sb->s_anon)) {
@@ -1147,7 +1147,7 @@ resume:
* loop in shrink_dcache_parent() might not make any progress
* and loop forever.
*/
- if (dentry->d_count) {
+ if (d_count(dentry)) {
dentry_lru_del(dentry);
} else if (!(dentry->d_flags & DCACHE_SHRINK_LIST)) {
dentry_lru_move_list(dentry, dispose);
@@ -1269,7 +1269,7 @@ struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
smp_wmb();
dentry->d_name.name = dname;
- dentry->d_count = 1;
+ dentry->d_lockcnt.refcnt = 1;
dentry->d_flags = 0;
spin_lock_init(&dentry->d_lock);
seqcount_init(&dentry->d_seq);
@@ -1970,7 +1970,7 @@ struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name)
goto next;
}
- dentry->d_count++;
+ dentry->d_lockcnt.refcnt++;
found = dentry;
spin_unlock(&dentry->d_lock);
break;
@@ -2069,7 +2069,7 @@ again:
spin_lock(&dentry->d_lock);
inode = dentry->d_inode;
isdir = S_ISDIR(inode->i_mode);
- if (dentry->d_count == 1) {
+ if (d_count(dentry) == 1) {
if (!spin_trylock(&inode->i_lock)) {
spin_unlock(&dentry->d_lock);
cpu_relax();
@@ -2937,7 +2937,7 @@ resume:
}
if (!(dentry->d_flags & DCACHE_GENOCIDE)) {
dentry->d_flags |= DCACHE_GENOCIDE;
- dentry->d_count--;
+ dentry->d_lockcnt.refcnt--;
}
spin_unlock(&dentry->d_lock);
}
@@ -2945,7 +2945,7 @@ resume:
struct dentry *child = this_parent;
if (!(this_parent->d_flags & DCACHE_GENOCIDE)) {
this_parent->d_flags |= DCACHE_GENOCIDE;
- this_parent->d_count--;
+ this_parent->d_lockcnt.refcnt--;
}
this_parent = try_to_ascend(this_parent, locked, seq);
if (!this_parent)
diff --git a/fs/namei.c b/fs/namei.c
index 8b61d10..28e5152 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -536,8 +536,8 @@ static int unlazy_walk(struct nameidata *nd, struct dentry *dentry)
* a reference at this point.
*/
BUG_ON(!IS_ROOT(dentry) && dentry->d_parent != parent);
- BUG_ON(!parent->d_count);
- parent->d_count++;
+ BUG_ON(!d_count(parent));
+ parent->d_lockcnt.refcnt++;
spin_unlock(&dentry->d_lock);
}
spin_unlock(&parent->d_lock);
@@ -3327,7 +3327,7 @@ void dentry_unhash(struct dentry *dentry)
{
shrink_dcache_parent(dentry);
spin_lock(&dentry->d_lock);
- if (dentry->d_count == 1)
+ if (d_count(dentry) == 1)
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
}
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index b90337c..20e6f2e 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -9,6 +9,7 @@
#include <linux/seqlock.h>
#include <linux/cache.h>
#include <linux/rcupdate.h>
+#include <linux/spinlock_refcount.h>
struct nameidata;
struct path;
@@ -112,8 +113,7 @@ struct dentry {
unsigned char d_iname[DNAME_INLINE_LEN]; /* small names */
/* Ref lookup also touches following */
- unsigned int d_count; /* protected by d_lock */
- spinlock_t d_lock; /* per dentry lock */
+ struct lockref d_lockcnt; /* per dentry lock & count */
const struct dentry_operations *d_op;
struct super_block *d_sb; /* The root of the dentry tree */
unsigned long d_time; /* used by d_revalidate */
@@ -132,6 +132,11 @@ struct dentry {
};
/*
+ * Define macros to access the name-changed spinlock
+ */
+#define d_lock d_lockcnt.lock
+
+/*
* dentry->d_lock spinlock nesting subclasses:
*
* 0: normal
@@ -318,7 +323,7 @@ static inline int __d_rcu_to_refcount(struct dentry *dentry, unsigned seq)
assert_spin_locked(&dentry->d_lock);
if (!read_seqcount_retry(&dentry->d_seq, seq)) {
ret = 1;
- dentry->d_count++;
+ dentry->d_lockcnt.refcnt++;
}
return ret;
@@ -326,7 +331,7 @@ static inline int __d_rcu_to_refcount(struct dentry *dentry, unsigned seq)
static inline unsigned d_count(const struct dentry *dentry)
{
- return dentry->d_count;
+ return dentry->d_lockcnt.refcnt;
}
/* validate "insecure" dentry pointer */
@@ -356,7 +361,7 @@ extern char *dentry_path(struct dentry *, char *, int);
static inline struct dentry *dget_dlock(struct dentry *dentry)
{
if (dentry)
- dentry->d_count++;
+ dentry->d_lockcnt.refcnt++;
return dentry;
}
--
1.7.1
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