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fs: dcache scale dentry refcount

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Make d_count non-atomic and protect it with d_lock. This allows us to ensure a
0 refcount dentry remains 0 without dcache_lock. It is also fairly natural when
we start protecting many other dentry members with d_lock.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
This commit is contained in:
Nick Piggin
2011-01-07 17:49:32 +11:00
parent 2304450783
commit b7ab39f631
21 changed files with 126 additions and 69 deletions
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29
include/linux/dcache.h
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@@ -87,7 +87,7 @@ full_name_hash(const unsigned char *name, unsigned int len)
#endif
struct dentry {
atomic_t d_count;
unsigned int d_count; /* protected by d_lock */
unsigned int d_flags; /* protected by d_lock */
spinlock_t d_lock; /* per dentry lock */
int d_mounted;
@@ -297,17 +297,28 @@ extern char *dentry_path(struct dentry *, char *, int);
* needs and they take necessary precautions) you should hold dcache_lock
* and call dget_locked() instead of dget().
*/
static inline struct dentry *dget_dlock(struct dentry *dentry)
{
if (dentry) {
BUG_ON(!dentry->d_count);
dentry->d_count++;
}
return dentry;
}
static inline struct dentry *dget(struct dentry *dentry)
{
if (dentry) {
BUG_ON(!atomic_read(&dentry->d_count));
atomic_inc(&dentry->d_count);
spin_lock(&dentry->d_lock);
dget_dlock(dentry);
spin_unlock(&dentry->d_lock);
}
return dentry;
}
extern struct dentry * dget_locked(struct dentry *);
extern struct dentry * dget_locked_dlock(struct dentry *);
extern struct dentry *dget_parent(struct dentry *dentry);
/**
* d_unhashed - is dentry hashed
@@ -338,16 +349,6 @@ static inline void dont_mount(struct dentry *dentry)
spin_unlock(&dentry->d_lock);
}
static inline struct dentry *dget_parent(struct dentry *dentry)
{
struct dentry *ret;
spin_lock(&dentry->d_lock);
ret = dget(dentry->d_parent);
spin_unlock(&dentry->d_lock);
return ret;
}
extern void dput(struct dentry *);
static inline int d_mountpoint(struct dentry *dentry)