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linux-sg2042
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fs: dcache scale dentry refcount 

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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
arch/powerpc/platforms/cell/spufs/inode.c
View File

@ -162,7 +162,7 @@ static void spufs_prune_dir(struct dentry *dir)
spin_lock(&dcache_lock);
spin_lock(&dentry->d_lock);
if (!(d_unhashed(dentry)) && dentry->d_inode) {
dget_locked(dentry);
dget_locked_dlock(dentry);
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
simple_unlink(dir->d_inode, dentry);

2
drivers/infiniband/hw/ipath/ipath_fs.c
View File

@ -280,7 +280,7 @@ static int remove_file(struct dentry *parent, char *name)
spin_lock(&dcache_lock);
spin_lock(&tmp->d_lock);
if (!(d_unhashed(tmp) && tmp->d_inode)) {
dget_locked(tmp);
dget_locked_dlock(tmp);
__d_drop(tmp);
spin_unlock(&tmp->d_lock);
spin_unlock(&dcache_lock);

2
drivers/infiniband/hw/qib/qib_fs.c
View File

@ -456,7 +456,7 @@ static int remove_file(struct dentry *parent, char *name)
spin_lock(&dcache_lock);
spin_lock(&tmp->d_lock);
if (!(d_unhashed(tmp) && tmp->d_inode)) {
dget_locked(tmp);
dget_locked_dlock(tmp);
__d_drop(tmp);
spin_unlock(&tmp->d_lock);
spin_unlock(&dcache_lock);

8
fs/autofs4/expire.c
View File

@ -198,7 +198,7 @@ static int autofs4_tree_busy(struct vfsmount *mnt,
else
ino_count++;
if (atomic_read(&p->d_count) > ino_count) {
if (p->d_count > ino_count) {
top_ino->last_used = jiffies;
dput(p);
return 1;
@ -347,7 +347,7 @@ struct dentry *autofs4_expire_indirect(struct super_block *sb,
/* Path walk currently on this dentry? */
ino_count = atomic_read(&ino->count) + 2;
if (atomic_read(&dentry->d_count) > ino_count)
if (dentry->d_count > ino_count)
goto next;
/* Can we umount this guy */
@ -369,7 +369,7 @@ struct dentry *autofs4_expire_indirect(struct super_block *sb,
if (!exp_leaves) {
/* Path walk currently on this dentry? */
ino_count = atomic_read(&ino->count) + 1;
if (atomic_read(&dentry->d_count) > ino_count)
if (dentry->d_count > ino_count)
goto next;
if (!autofs4_tree_busy(mnt, dentry, timeout, do_now)) {
@ -383,7 +383,7 @@ struct dentry *autofs4_expire_indirect(struct super_block *sb,
} else {
/* Path walk currently on this dentry? */
ino_count = atomic_read(&ino->count) + 1;
if (atomic_read(&dentry->d_count) > ino_count)
if (dentry->d_count > ino_count)
goto next;
expired = autofs4_check_leaves(mnt, dentry, timeout, do_now);

6
fs/autofs4/root.c
View File

@ -436,7 +436,7 @@ static struct dentry *autofs4_lookup_active(struct dentry *dentry)
spin_lock(&active->d_lock);
/* Already gone? */
if (atomic_read(&active->d_count) == 0)
if (active->d_count == 0)
goto next;
qstr = &active->d_name;
@ -452,7 +452,7 @@ static struct dentry *autofs4_lookup_active(struct dentry *dentry)
goto next;
if (d_unhashed(active)) {
dget(active);
dget_dlock(active);
spin_unlock(&active->d_lock);
spin_unlock(&sbi->lookup_lock);
spin_unlock(&dcache_lock);
@ -507,7 +507,7 @@ static struct dentry *autofs4_lookup_expiring(struct dentry *dentry)
goto next;
if (d_unhashed(expiring)) {
dget(expiring);
dget_dlock(expiring);
spin_unlock(&expiring->d_lock);
spin_unlock(&sbi->lookup_lock);
spin_unlock(&dcache_lock);

4
fs/ceph/dir.c
View File

@ -150,7 +150,9 @@ more:
di = ceph_dentry(dentry);
}
atomic_inc(&dentry->d_count);
spin_lock(&dentry->d_lock);
dentry->d_count++;
spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
dout(" %llu (%llu) dentry %p %.*s %p\n", di->offset, filp->f_pos,

4
fs/ceph/inode.c
View File

@ -879,8 +879,8 @@ static struct dentry *splice_dentry(struct dentry *dn, struct inode *in,
} else if (realdn) {
dout("dn %p (%d) spliced with %p (%d) "
"inode %p ino %llx.%llx\n",
dn, atomic_read(&dn->d_count),
realdn, atomic_read(&realdn->d_count),
dn, dn->d_count,
realdn, realdn->d_count,
realdn->d_inode, ceph_vinop(realdn->d_inode));
dput(dn);
dn = realdn;

2
fs/ceph/mds_client.c
View File

@ -1486,7 +1486,7 @@ retry:
*base = ceph_ino(temp->d_inode);
*plen = len;
dout("build_path on %p %d built %llx '%.*s'\n",
dentry, atomic_read(&dentry->d_count), *base, len, path);
dentry, dentry->d_count, *base, len, path);
return path;
}

2
fs/coda/dir.c
View File

@ -559,7 +559,7 @@ static int coda_dentry_revalidate(struct dentry *de, struct nameidata *nd)
if (cii->c_flags & C_FLUSH)
coda_flag_inode_children(inode, C_FLUSH);
if (atomic_read(&de->d_count) > 1)
if (de->d_count > 1)
/* pretend it's valid, but don't change the flags */
goto out;

3
fs/configfs/dir.c
View File

@ -394,8 +394,7 @@ static void remove_dir(struct dentry * d)
if (d->d_inode)
simple_rmdir(parent->d_inode,d);
pr_debug(" o %s removing done (%d)\n",d->d_name.name,
atomic_read(&d->d_count));
pr_debug(" o %s removing done (%d)\n",d->d_name.name, d->d_count);
dput(parent);
}

2
fs/configfs/inode.c
View File

@ -253,7 +253,7 @@ void configfs_drop_dentry(struct configfs_dirent * sd, struct dentry * parent)
spin_lock(&dcache_lock);
spin_lock(&dentry->d_lock);
if (!(d_unhashed(dentry) && dentry->d_inode)) {
dget_locked(dentry);
dget_locked_dlock(dentry);
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);

106
fs/dcache.c
View File

@ -45,6 +45,7 @@
* - d_flags
* - d_name
* - d_lru
* - d_count
*
* Ordering:
* dcache_lock
@ -125,6 +126,7 @@ static void __d_free(struct rcu_head *head)
*/
static void d_free(struct dentry *dentry)
{
BUG_ON(dentry->d_count);
this_cpu_dec(nr_dentry);
if (dentry->d_op && dentry->d_op->d_release)
dentry->d_op->d_release(dentry);
@ -222,8 +224,11 @@ static struct dentry *d_kill(struct dentry *dentry)
struct dentry *parent;
list_del(&dentry->d_u.d_child);
/*drops the locks, at that point nobody can reach this dentry */
dentry_iput(dentry);
/*
* dentry_iput drops the locks, at which point nobody (except
* transient RCU lookups) can reach this dentry.
*/
if (IS_ROOT(dentry))
parent = NULL;
else
@ -303,13 +308,23 @@ void dput(struct dentry *dentry)
return;
repeat:
if (atomic_read(&dentry->d_count) == 1)
if (dentry->d_count == 1)
might_sleep();
if (!atomic_dec_and_lock(&dentry->d_count, &dcache_lock))
return;
spin_lock(&dentry->d_lock);
if (atomic_read(&dentry->d_count)) {
if (dentry->d_count == 1) {
if (!spin_trylock(&dcache_lock)) {
/*
* Something of a livelock possibility we could avoid
* by taking dcache_lock and trying again, but we
* want to reduce dcache_lock anyway so this will
* get improved.
*/
spin_unlock(&dentry->d_lock);
goto repeat;
}
}
dentry->d_count--;
if (dentry->d_count) {
spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
return;
@ -389,7 +404,7 @@ int d_invalidate(struct dentry * dentry)
* working directory or similar).
*/
spin_lock(&dentry->d_lock);
if (atomic_read(&dentry->d_count) > 1) {
if (dentry->d_count > 1) {
if (dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)) {
spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
@ -404,29 +419,61 @@ int d_invalidate(struct dentry * dentry)
}
EXPORT_SYMBOL(d_invalidate);
/* This should be called _only_ with dcache_lock held */
/* This must be called with dcache_lock and d_lock held */
static inline struct dentry * __dget_locked_dlock(struct dentry *dentry)
{
atomic_inc(&dentry->d_count);
dentry->d_count++;
dentry_lru_del(dentry);
return dentry;
}
/* This should be called _only_ with dcache_lock held */
static inline struct dentry * __dget_locked(struct dentry *dentry)
{
atomic_inc(&dentry->d_count);
spin_lock(&dentry->d_lock);
dentry_lru_del(dentry);
__dget_locked_dlock(dentry);
spin_unlock(&dentry->d_lock);
return dentry;
}
struct dentry * dget_locked_dlock(struct dentry *dentry)
{
return __dget_locked_dlock(dentry);
}
struct dentry * dget_locked(struct dentry *dentry)
{
return __dget_locked(dentry);
}
EXPORT_SYMBOL(dget_locked);
struct dentry *dget_parent(struct dentry *dentry)
{
struct dentry *ret;
repeat:
spin_lock(&dentry->d_lock);
ret = dentry->d_parent;
if (!ret)
goto out;
if (dentry == ret) {
ret->d_count++;
goto out;
}
if (!spin_trylock(&ret->d_lock)) {
spin_unlock(&dentry->d_lock);
cpu_relax();
goto repeat;
}
BUG_ON(!ret->d_count);
ret->d_count++;
spin_unlock(&ret->d_lock);
out:
spin_unlock(&dentry->d_lock);
return ret;
}
EXPORT_SYMBOL(dget_parent);
/**
* d_find_alias - grab a hashed alias of inode
* @inode: inode in question
@ -495,7 +542,7 @@ restart:
spin_lock(&dcache_lock);
list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
spin_lock(&dentry->d_lock);
if (!atomic_read(&dentry->d_count)) {
if (!dentry->d_count) {
__dget_locked_dlock(dentry);
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
@ -530,7 +577,10 @@ static void prune_one_dentry(struct dentry * dentry)
*/
while (dentry) {
spin_lock(&dcache_lock);
if (!atomic_dec_and_lock(&dentry->d_count, &dentry->d_lock)) {
spin_lock(&dentry->d_lock);
dentry->d_count--;
if (dentry->d_count) {
spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
return;
}
@ -562,7 +612,7 @@ 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 (atomic_read(&dentry->d_count)) {
if (dentry->d_count) {
spin_unlock(&dentry->d_lock);
continue;
}
@ -783,7 +833,7 @@ static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
do {
struct inode *inode;
if (atomic_read(&dentry->d_count) != 0) {
if (dentry->d_count != 0) {
printk(KERN_ERR
"BUG: Dentry %p{i=%lx,n=%s}"
" still in use (%d)"
@ -792,7 +842,7 @@ static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
dentry->d_inode ?
dentry->d_inode->i_ino : 0UL,
dentry->d_name.name,
atomic_read(&dentry->d_count),
dentry->d_count,
dentry->d_sb->s_type->name,
dentry->d_sb->s_id);
BUG();
@ -802,7 +852,9 @@ static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
parent = NULL;
else {
parent = dentry->d_parent;
atomic_dec(&parent->d_count);
spin_lock(&parent->d_lock);
parent->d_count--;
spin_unlock(&parent->d_lock);
}
list_del(&dentry->d_u.d_child);
@ -853,7 +905,9 @@ void shrink_dcache_for_umount(struct super_block *sb)
dentry = sb->s_root;
sb->s_root = NULL;
atomic_dec(&dentry->d_count);
spin_lock(&dentry->d_lock);
dentry->d_count--;
spin_unlock(&dentry->d_lock);
shrink_dcache_for_umount_subtree(dentry);
while (!hlist_empty(&sb->s_anon)) {
@ -950,7 +1004,7 @@ resume:
* move only zero ref count dentries to the end
* of the unused list for prune_dcache
*/
if (!atomic_read(&dentry->d_count)) {
if (!dentry->d_count) {
dentry_lru_move_tail(dentry);
found++;
} else {
@ -1068,7 +1122,7 @@ struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
memcpy(dname, name->name, name->len);
dname[name->len] = 0;
atomic_set(&dentry->d_count, 1);
dentry->d_count = 1;
dentry->d_flags = DCACHE_UNHASHED;
spin_lock_init(&dentry->d_lock);
dentry->d_inode = NULL;
@ -1556,7 +1610,7 @@ struct dentry * __d_lookup(struct dentry * parent, struct qstr * name)
goto next;
}
atomic_inc(&dentry->d_count);
dentry->d_count++;
found = dentry;
spin_unlock(&dentry->d_lock);
break;
@ -1653,7 +1707,7 @@ void d_delete(struct dentry * dentry)
spin_lock(&dcache_lock);
spin_lock(&dentry->d_lock);
isdir = S_ISDIR(dentry->d_inode->i_mode);
if (atomic_read(&dentry->d_count) == 1) {
if (dentry->d_count == 1) {
dentry->d_flags &= ~DCACHE_CANT_MOUNT;
dentry_iput(dentry);
fsnotify_nameremove(dentry, isdir);
@ -2494,11 +2548,15 @@ resume:
this_parent = dentry;
goto repeat;
}
atomic_dec(&dentry->d_count);
spin_lock(&dentry->d_lock);
dentry->d_count--;
spin_unlock(&dentry->d_lock);
}
if (this_parent != root) {
next = this_parent->d_u.d_child.next;
atomic_dec(&this_parent->d_count);
spin_lock(&this_parent->d_lock);
this_parent->d_count--;
spin_unlock(&this_parent->d_lock);
this_parent = this_parent->d_parent;
goto resume;
}

2
fs/ecryptfs/inode.c
View File

@ -260,7 +260,7 @@ int ecryptfs_lookup_and_interpose_lower(struct dentry *ecryptfs_dentry,
ecryptfs_dentry->d_parent));
lower_inode = lower_dentry->d_inode;
fsstack_copy_attr_atime(ecryptfs_dir_inode, lower_dir_dentry->d_inode);
BUG_ON(!atomic_read(&lower_dentry->d_count));
BUG_ON(!lower_dentry->d_count);
ecryptfs_set_dentry_private(ecryptfs_dentry,
kmem_cache_alloc(ecryptfs_dentry_info_cache,
GFP_KERNEL));

2
fs/locks.c
View File

@ -1389,7 +1389,7 @@ int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
if ((arg == F_RDLCK) && (atomic_read(&inode->i_writecount) > 0))
goto out;
if ((arg == F_WRLCK)
&& ((atomic_read(&dentry->d_count) > 1)
&& ((dentry->d_count > 1)
|| (atomic_read(&inode->i_count) > 1)))
goto out;
}

2
fs/namei.c
View File

@ -2133,7 +2133,7 @@ void dentry_unhash(struct dentry *dentry)
shrink_dcache_parent(dentry);
spin_lock(&dcache_lock);
spin_lock(&dentry->d_lock);
if (atomic_read(&dentry->d_count) == 2)
if (dentry->d_count == 2)
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);

6
fs/nfs/dir.c
View File

@ -1720,7 +1720,7 @@ static int nfs_unlink(struct inode *dir, struct dentry *dentry)
spin_lock(&dcache_lock);
spin_lock(&dentry->d_lock);
if (atomic_read(&dentry->d_count) > 1) {
if (dentry->d_count > 1) {
spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
/* Start asynchronous writeout of the inode */
@ -1868,7 +1868,7 @@ static int nfs_rename(struct inode *old_dir, struct dentry *old_dentry,
dfprintk(VFS, "NFS: rename(%s/%s -> %s/%s, ct=%d)\n",
old_dentry->d_parent->d_name.name, old_dentry->d_name.name,
new_dentry->d_parent->d_name.name, new_dentry->d_name.name,
atomic_read(&new_dentry->d_count));
new_dentry->d_count);
/*
* For non-directories, check whether the target is busy and if so,
@ -1886,7 +1886,7 @@ static int nfs_rename(struct inode *old_dir, struct dentry *old_dentry,
rehash = new_dentry;
}
if (atomic_read(&new_dentry->d_count) > 2) {
if (new_dentry->d_count > 2) {
int err;
/* copy the target dentry's name */

2
fs/nfs/unlink.c
View File

@ -496,7 +496,7 @@ nfs_sillyrename(struct inode *dir, struct dentry *dentry)
dfprintk(VFS, "NFS: silly-rename(%s/%s, ct=%d)\n",
dentry->d_parent->d_name.name, dentry->d_name.name,
atomic_read(&dentry->d_count));
dentry->d_count);
nfs_inc_stats(dir, NFSIOS_SILLYRENAME);
/*

5
fs/nfsd/vfs.c
View File

@ -1756,8 +1756,7 @@ nfsd_rename(struct svc_rqst *rqstp, struct svc_fh *ffhp, char *fname, int flen,
goto out_dput_new;
if (svc_msnfs(ffhp) &&
((atomic_read(&odentry->d_count) > 1)
|| (atomic_read(&ndentry->d_count) > 1))) {
((odentry->d_count > 1) || (ndentry->d_count > 1))) {
host_err = -EPERM;
goto out_dput_new;
}
@ -1843,7 +1842,7 @@ nfsd_unlink(struct svc_rqst *rqstp, struct svc_fh *fhp, int type,
if (type != S_IFDIR) { /* It's UNLINK */
#ifdef MSNFS
if ((fhp->fh_export->ex_flags & NFSEXP_MSNFS) &&
(atomic_read(&rdentry->d_count) > 1)) {
(rdentry->d_count > 1)) {
host_err = -EPERM;
} else
#endif

2
fs/nilfs2/super.c
View File

@ -838,7 +838,7 @@ static int nilfs_attach_snapshot(struct super_block *s, __u64 cno,
static int nilfs_tree_was_touched(struct dentry *root_dentry)
{
return atomic_read(&root_dentry->d_count) > 1;
return root_dentry->d_count > 1;
}
/**

29
include/linux/dcache.h
View File

@ -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)

2
kernel/cgroup.c
View File

@ -3655,9 +3655,7 @@ again:
list_del(&cgrp->sibling);
cgroup_unlock_hierarchy(cgrp->root);
spin_lock(&cgrp->dentry->d_lock);
d = dget(cgrp->dentry);
spin_unlock(&d->d_lock);
cgroup_d_remove_dir(d);
dput(d);