[PATCH 2.5.44] dcache_rcu

Maneesh Soni (maneesh@in.ibm.com)
Wed, 30 Oct 2002 16:19:12 +0530

Hello Viro,

Please consider forwarding the following patch ito Linus for dcache lookup
using Read Copy Update. The patch has been there in -mm kernel since
2.5.37-mm1. The patch is stable. A couple of bugs reported are solved. It
helps a great deal on higher end SMP machines and there is no performance
regression on UP and lower end SMP machines as seen in Dipankar's kernbench
numbers.

http://marc.theaimsgroup.com/?l=linux-kernel&m=103462075416638&w=2

Regards,
Maneesh

diff -urN linux-2.5.44-base/drivers/usb/core/inode.c linux-2.5.44-dc12/drivers/usb/core/inode.c
--- linux-2.5.44-base/drivers/usb/core/inode.c Sat Oct 19 09:31:09 2002
+++ linux-2.5.44-dc12/drivers/usb/core/inode.c Wed Oct 30 15:20:09 2002
@@ -254,7 +254,7 @@
if (atomic_read(&dentry->d_count) != 2)
break;
case 2:
- list_del_init(&dentry->d_hash);
+ __d_drop(dentry);
}
spin_unlock(&dcache_lock);
}
diff -urN linux-2.5.44-base/fs/autofs4/root.c linux-2.5.44-dc12/fs/autofs4/root.c
--- linux-2.5.44-base/fs/autofs4/root.c Sat Oct 19 09:31:08 2002
+++ linux-2.5.44-dc12/fs/autofs4/root.c Wed Oct 30 15:20:09 2002
@@ -418,7 +418,7 @@
unlock_kernel();
return -ENOTEMPTY;
}
- list_del_init(&dentry->d_hash);
+ __d_drop(dentry);
spin_unlock(&dcache_lock);

dput(ino->dentry);
diff -urN linux-2.5.44-base/fs/dcache.c linux-2.5.44-dc12/fs/dcache.c
--- linux-2.5.44-base/fs/dcache.c Sat Oct 19 09:31:13 2002
+++ linux-2.5.44-dc12/fs/dcache.c Wed Oct 30 15:21:17 2002
@@ -23,6 +23,7 @@
#include <linux/smp_lock.h>
#include <linux/cache.h>
#include <linux/module.h>
+#include <linux/rcupdate.h>

#include <asm/uaccess.h>

@@ -55,14 +56,21 @@
.age_limit = 45,
};

+static void d_callback(void *arg)
+{
+ struct dentry * dentry = (struct dentry *)arg;
+
+ if (dname_external(dentry))
+ kfree(dentry->d_name.name);
+ kmem_cache_free(dentry_cache, dentry);
+}
+
/* no dcache_lock, please */
static inline void d_free(struct dentry *dentry)
{
if (dentry->d_op && dentry->d_op->d_release)
dentry->d_op->d_release(dentry);
- if (dname_external(dentry))
- kfree(dentry->d_name.name);
- kmem_cache_free(dentry_cache, dentry);
+ call_rcu(&dentry->d_rcu, d_callback, dentry);
dentry_stat.nr_dentry--;
}

@@ -124,9 +132,13 @@
if (!atomic_dec_and_lock(&dentry->d_count, &dcache_lock))
return;

- /* dput on a free dentry? */
- if (!list_empty(&dentry->d_lru))
- BUG();
+ spin_lock(&dentry->d_lock);
+ if (atomic_read(&dentry->d_count)) {
+ spin_unlock(&dentry->d_lock);
+ spin_unlock(&dcache_lock);
+ return;
+ }
+
/*
* AV: ->d_delete() is _NOT_ allowed to block now.
*/
@@ -135,20 +147,29 @@
goto unhash_it;
}
/* Unreachable? Get rid of it */
- if (list_empty(&dentry->d_hash))
+ if (d_unhashed(dentry))
goto kill_it;
- list_add(&dentry->d_lru, &dentry_unused);
- dentry_stat.nr_unused++;
- dentry->d_vfs_flags |= DCACHE_REFERENCED;
+ if (list_empty(&dentry->d_lru)) {
+ dentry->d_vfs_flags &= ~DCACHE_REFERENCED;
+ list_add(&dentry->d_lru, &dentry_unused);
+ dentry_stat.nr_unused++;
+ }
+ spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
return;

unhash_it:
- list_del_init(&dentry->d_hash);
+ dentry->d_vfs_flags |= DCACHE_UNHASHED;
+ list_del_rcu(&dentry->d_hash);

kill_it: {
struct dentry *parent;
+ if (!list_empty(&dentry->d_lru)) {
+ list_del(&dentry->d_lru);
+ dentry_stat.nr_unused--;
+ }
list_del(&dentry->d_child);
+ spin_unlock(&dentry->d_lock);
/* drops the lock, at that point nobody can reach this dentry */
dentry_iput(dentry);
parent = dentry->d_parent;
@@ -178,7 +199,7 @@
* If it's already been dropped, return OK.
*/
spin_lock(&dcache_lock);
- if (list_empty(&dentry->d_hash)) {
+ if (d_unhashed(dentry)) {
spin_unlock(&dcache_lock);
return 0;
}
@@ -208,9 +229,9 @@
return -EBUSY;
}
}
-
- list_del_init(&dentry->d_hash);
+ __d_drop(dentry);
spin_unlock(&dcache_lock);
+
return 0;
}

@@ -219,6 +240,7 @@
static inline struct dentry * __dget_locked(struct dentry *dentry)
{
atomic_inc(&dentry->d_count);
+ dentry->d_vfs_flags |= DCACHE_REFERENCED;
if (atomic_read(&dentry->d_count) == 1) {
dentry_stat.nr_unused--;
list_del_init(&dentry->d_lru);
@@ -256,7 +278,7 @@
tmp = next;
next = tmp->next;
alias = list_entry(tmp, struct dentry, d_alias);
- if (!list_empty(&alias->d_hash)) {
+ if (!d_unhashed(alias)) {
if (alias->d_flags & DCACHE_DISCONNECTED)
discon_alias = alias;
else {
@@ -286,8 +308,8 @@
struct dentry *dentry = list_entry(tmp, struct dentry, d_alias);
if (!atomic_read(&dentry->d_count)) {
__dget_locked(dentry);
+ __d_drop(dentry);
spin_unlock(&dcache_lock);
- d_drop(dentry);
dput(dentry);
goto restart;
}
@@ -305,8 +327,9 @@
{
struct dentry * parent;

- list_del_init(&dentry->d_hash);
+ __d_drop(dentry);
list_del(&dentry->d_child);
+ spin_unlock(&dentry->d_lock);
dentry_iput(dentry);
parent = dentry->d_parent;
d_free(dentry);
@@ -339,18 +362,20 @@
if (tmp == &dentry_unused)
break;
list_del_init(tmp);
+ dentry_stat.nr_unused--;
dentry = list_entry(tmp, struct dentry, d_lru);

+ spin_lock(&dentry->d_lock);
/* If the dentry was recently referenced, don't free it. */
if (dentry->d_vfs_flags & DCACHE_REFERENCED) {
dentry->d_vfs_flags &= ~DCACHE_REFERENCED;
- list_add(&dentry->d_lru, &dentry_unused);
+ if (!atomic_read(&dentry->d_count)) {
+ list_add(&dentry->d_lru, &dentry_unused);
+ dentry_stat.nr_unused++;
+ }
+ spin_unlock(&dentry->d_lock);
continue;
}
- dentry_stat.nr_unused--;
-
- /* Unused dentry with a count? */
- BUG_ON(atomic_read(&dentry->d_count));
prune_one_dentry(dentry);
}
spin_unlock(&dcache_lock);
@@ -410,10 +435,13 @@
dentry = list_entry(tmp, struct dentry, d_lru);
if (dentry->d_sb != sb)
continue;
- if (atomic_read(&dentry->d_count))
- continue;
dentry_stat.nr_unused--;
list_del_init(tmp);
+ spin_lock(&dentry->d_lock);
+ if (atomic_read(&dentry->d_count)) {
+ spin_unlock(&dentry->d_lock);
+ continue;
+ }
prune_one_dentry(dentry);
goto repeat;
}
@@ -493,8 +521,8 @@
struct list_head *tmp = next;
struct dentry *dentry = list_entry(tmp, struct dentry, d_child);
next = tmp->next;
+ list_del_init(&dentry->d_lru);
if (!atomic_read(&dentry->d_count)) {
- list_del(&dentry->d_lru);
list_add(&dentry->d_lru, dentry_unused.prev);
found++;
}
@@ -557,8 +585,8 @@
spin_lock(&dcache_lock);
list_for_each(lp, head) {
struct dentry *this = list_entry(lp, struct dentry, d_hash);
+ list_del(&this->d_lru);
if (!atomic_read(&this->d_count)) {
- list_del(&this->d_lru);
list_add_tail(&this->d_lru, &dentry_unused);
found++;
}
@@ -626,7 +654,8 @@
str[name->len] = 0;

atomic_set(&dentry->d_count, 1);
- dentry->d_vfs_flags = 0;
+ dentry->d_vfs_flags = DCACHE_UNHASHED;
+ dentry->d_lock = SPIN_LOCK_UNLOCKED;
dentry->d_flags = 0;
dentry->d_inode = NULL;
dentry->d_parent = NULL;
@@ -759,12 +788,15 @@
res = tmp;
tmp = NULL;
if (res) {
+ spin_lock(&res->d_lock);
res->d_sb = inode->i_sb;
res->d_parent = res;
res->d_inode = inode;
res->d_flags |= DCACHE_DISCONNECTED;
+ res->d_vfs_flags &= ~DCACHE_UNHASHED;
list_add(&res->d_alias, &inode->i_dentry);
list_add(&res->d_hash, &inode->i_sb->s_anon);
+ spin_unlock(&res->d_lock);
}
inode = NULL; /* don't drop reference */
}
@@ -833,30 +865,16 @@

struct dentry * d_lookup(struct dentry * parent, struct qstr * name)
{
- struct dentry * dentry;
- spin_lock(&dcache_lock);
- dentry = __d_lookup(parent,name);
- if (dentry)
- __dget_locked(dentry);
- spin_unlock(&dcache_lock);
- return dentry;
-}
-
-struct dentry * __d_lookup(struct dentry * parent, struct qstr * name)
-{
-
unsigned int len = name->len;
unsigned int hash = name->hash;
const unsigned char *str = name->name;
struct list_head *head = d_hash(parent,hash);
struct list_head *tmp;
+ struct dentry *found = NULL;

- tmp = head->next;
- for (;;) {
+ rcu_read_lock();
+ __list_for_each_rcu(tmp, head) {
struct dentry * dentry = list_entry(tmp, struct dentry, d_hash);
- if (tmp == head)
- break;
- tmp = tmp->next;
if (dentry->d_name.hash != hash)
continue;
if (dentry->d_parent != parent)
@@ -870,9 +888,14 @@
if (memcmp(dentry->d_name.name, str, len))
continue;
}
- return dentry;
- }
- return NULL;
+ spin_lock(&dentry->d_lock);
+ if (!d_unhashed(dentry))
+ found = dget(dentry);
+ spin_unlock(&dentry->d_lock);
+ break;
+ }
+ rcu_read_unlock();
+ return found;
}

/**
@@ -911,7 +934,7 @@
lhp = base = d_hash(dparent, dentry->d_name.hash);
while ((lhp = lhp->next) != base) {
if (dentry == list_entry(lhp, struct dentry, d_hash)) {
- __dget_locked(dentry);
+ dget(dentry);
spin_unlock(&dcache_lock);
return 1;
}
@@ -948,17 +971,18 @@
* Are we the only user?
*/
spin_lock(&dcache_lock);
+ spin_lock(&dentry->d_lock);
if (atomic_read(&dentry->d_count) == 1) {
+ spin_unlock(&dentry->d_lock);
dentry_iput(dentry);
return;
}
- spin_unlock(&dcache_lock);

- /*
- * If not, just drop the dentry and let dput
- * pick up the tab..
- */
- d_drop(dentry);
+ if (!d_unhashed(dentry))
+ __d_drop(dentry);
+
+ spin_unlock(&dentry->d_lock);
+ spin_unlock(&dcache_lock);
}

/**
@@ -971,9 +995,10 @@
void d_rehash(struct dentry * entry)
{
struct list_head *list = d_hash(entry->d_parent, entry->d_name.hash);
- if (!list_empty(&entry->d_hash)) BUG();
spin_lock(&dcache_lock);
- list_add(&entry->d_hash, list);
+ if (!list_empty(&entry->d_hash) && !d_unhashed(entry)) BUG();
+ entry->d_vfs_flags &= ~DCACHE_UNHASHED;
+ list_add_rcu(&entry->d_hash, list);
spin_unlock(&dcache_lock);
}

@@ -1043,7 +1068,7 @@
list_add(&dentry->d_hash, &target->d_hash);

/* Unhash the target: dput() will then get rid of it */
- list_del_init(&target->d_hash);
+ __d_drop(target);

list_del(&dentry->d_child);
list_del(&target->d_child);
@@ -1095,7 +1120,7 @@

*--end = '\0';
buflen--;
- if (!IS_ROOT(dentry) && list_empty(&dentry->d_hash)) {
+ if (!IS_ROOT(dentry) && d_unhashed(dentry)) {
buflen -= 10;
end -= 10;
memcpy(end, " (deleted)", 10);
@@ -1178,7 +1203,7 @@
error = -ENOENT;
/* Has the current directory has been unlinked? */
spin_lock(&dcache_lock);
- if (pwd->d_parent == pwd || !list_empty(&pwd->d_hash)) {
+ if (pwd->d_parent == pwd || !d_unhashed(pwd)) {
unsigned long len;
char * cwd;

diff -urN linux-2.5.44-base/fs/exec.c linux-2.5.44-dc12/fs/exec.c
--- linux-2.5.44-base/fs/exec.c Sat Oct 19 09:31:48 2002
+++ linux-2.5.44-dc12/fs/exec.c Wed Oct 30 15:20:09 2002
@@ -502,9 +502,9 @@

if (proc_dentry) {
spin_lock(&dcache_lock);
- if (!list_empty(&proc_dentry->d_hash)) {
+ if (!d_unhashed(proc_dentry)) {
dget_locked(proc_dentry);
- list_del_init(&proc_dentry->d_hash);
+ __d_drop(proc_dentry);
} else
proc_dentry = NULL;
spin_unlock(&dcache_lock);
diff -urN linux-2.5.44-base/fs/intermezzo/journal.c linux-2.5.44-dc12/fs/intermezzo/journal.c
--- linux-2.5.44-base/fs/intermezzo/journal.c Sat Oct 19 09:31:08 2002
+++ linux-2.5.44-dc12/fs/intermezzo/journal.c Wed Oct 30 15:20:09 2002
@@ -261,7 +261,7 @@

*--end = '\0';
buflen--;
- if (dentry->d_parent != dentry && list_empty(&dentry->d_hash)) {
+ if (dentry->d_parent != dentry && d_unhashed(dentry)) {
buflen -= 10;
end -= 10;
memcpy(end, " (deleted)", 10);
@@ -1518,7 +1518,7 @@
}

if (!dentry->d_inode || (dentry->d_inode->i_nlink == 0)
- || ((dentry->d_parent != dentry) && list_empty(&dentry->d_hash))) {
+ || ((dentry->d_parent != dentry) && d_unhashed(dentry))) {
EXIT;
return 0;
}
@@ -2129,7 +2129,7 @@
}

if (!dentry->d_inode || (dentry->d_inode->i_nlink == 0)
- || ((dentry->d_parent != dentry) && list_empty(&dentry->d_hash))) {
+ || ((dentry->d_parent != dentry) && d_unhashed(dentry))) {
EXIT;
return 0;
}
@@ -2391,7 +2391,7 @@
}

if (!dentry->d_inode || (dentry->d_inode->i_nlink == 0)
- || ((dentry->d_parent != dentry) && list_empty(&dentry->d_hash))) {
+ || ((dentry->d_parent != dentry) && d_unhashed(dentry))) {
EXIT;
return 0;
}
diff -urN linux-2.5.44-base/fs/libfs.c linux-2.5.44-dc12/fs/libfs.c
--- linux-2.5.44-base/fs/libfs.c Sat Oct 19 09:31:07 2002
+++ linux-2.5.44-dc12/fs/libfs.c Wed Oct 30 15:20:09 2002
@@ -70,7 +70,7 @@
while (n && p != &file->f_dentry->d_subdirs) {
struct dentry *next;
next = list_entry(p, struct dentry, d_child);
- if (!list_empty(&next->d_hash) && next->d_inode)
+ if (!d_unhashed(next) && next->d_inode)
n--;
p = p->next;
}
@@ -127,7 +127,7 @@
for (p=q->next; p != &dentry->d_subdirs; p=p->next) {
struct dentry *next;
next = list_entry(p, struct dentry, d_child);
- if (list_empty(&next->d_hash) || !next->d_inode)
+ if (d_unhashed(next) || !next->d_inode)
continue;

spin_unlock(&dcache_lock);
diff -urN linux-2.5.44-base/fs/namei.c linux-2.5.44-dc12/fs/namei.c
--- linux-2.5.44-base/fs/namei.c Sat Oct 19 09:31:22 2002
+++ linux-2.5.44-dc12/fs/namei.c Wed Oct 30 15:20:09 2002
@@ -286,27 +286,6 @@
return dentry;
}

-/*for fastwalking*/
-static inline void unlock_nd(struct nameidata *nd)
-{
- struct vfsmount *mnt = nd->old_mnt;
- struct dentry *dentry = nd->old_dentry;
- mntget(nd->mnt);
- dget_locked(nd->dentry);
- nd->old_mnt = NULL;
- nd->old_dentry = NULL;
- spin_unlock(&dcache_lock);
- dput(dentry);
- mntput(mnt);
-}
-
-static inline void lock_nd(struct nameidata *nd)
-{
- spin_lock(&dcache_lock);
- nd->old_mnt = nd->mnt;
- nd->old_dentry = nd->dentry;
-}
-
/*
* Short-cut version of permission(), for calling by
* path_walk(), when dcache lock is held. Combines parts
@@ -451,11 +430,18 @@
{
int res = 0;
while (d_mountpoint(*dentry)) {
- struct vfsmount *mounted = lookup_mnt(*mnt, *dentry);
- if (!mounted)
+ struct vfsmount *mounted;
+ spin_lock(&dcache_lock);
+ mounted = lookup_mnt(*mnt, *dentry);
+ if (!mounted) {
+ spin_unlock(&dcache_lock);
break;
- *mnt = mounted;
- *dentry = mounted->mnt_root;
+ }
+ *mnt = mntget(mounted);
+ spin_unlock(&dcache_lock);
+ dput(*dentry);
+ mntput(mounted->mnt_parent);
+ *dentry = dget(mounted->mnt_root);
res = 1;
}
return res;
@@ -488,17 +474,32 @@
{
while(1) {
struct vfsmount *parent;
+ struct dentry *old = *dentry;
+
+ read_lock(&current->fs->lock);
if (*dentry == current->fs->root &&
- *mnt == current->fs->rootmnt)
+ *mnt == current->fs->rootmnt) {
+ read_unlock(&current->fs->lock);
break;
+ }
+ read_unlock(&current->fs->lock);
+ spin_lock(&dcache_lock);
if (*dentry != (*mnt)->mnt_root) {
- *dentry = (*dentry)->d_parent;
+ *dentry = dget((*dentry)->d_parent);
+ spin_unlock(&dcache_lock);
+ dput(old);
break;
}
- parent=(*mnt)->mnt_parent;
- if (parent == *mnt)
+ parent = (*mnt)->mnt_parent;
+ if (parent == *mnt) {
+ spin_unlock(&dcache_lock);
break;
- *dentry=(*mnt)->mnt_mountpoint;
+ }
+ mntget(parent);
+ *dentry = dget((*mnt)->mnt_mountpoint);
+ spin_unlock(&dcache_lock);
+ dput(old);
+ mntput(*mnt);
*mnt = parent;
}
follow_mount(mnt, dentry);
@@ -515,14 +516,13 @@
* It _is_ time-critical.
*/
static int do_lookup(struct nameidata *nd, struct qstr *name,
- struct path *path, struct path *cached_path,
- int flags)
+ struct path *path, int flags)
{
struct vfsmount *mnt = nd->mnt;
- struct dentry *dentry = __d_lookup(nd->dentry, name);
+ struct dentry *dentry = d_lookup(nd->dentry, name);

if (!dentry)
- goto dcache_miss;
+ goto need_lookup;
if (dentry->d_op && dentry->d_op->d_revalidate)
goto need_revalidate;
done:
@@ -530,36 +530,21 @@
path->dentry = dentry;
return 0;

-dcache_miss:
- unlock_nd(nd);
-
need_lookup:
dentry = real_lookup(nd->dentry, name, LOOKUP_CONTINUE);
if (IS_ERR(dentry))
goto fail;
- mntget(mnt);
-relock:
- dput(cached_path->dentry);
- mntput(cached_path->mnt);
- cached_path->mnt = mnt;
- cached_path->dentry = dentry;
- lock_nd(nd);
goto done;

need_revalidate:
- mntget(mnt);
- dget_locked(dentry);
- unlock_nd(nd);
if (dentry->d_op->d_revalidate(dentry, flags))
- goto relock;
+ goto done;
if (d_invalidate(dentry))
- goto relock;
+ goto done;
dput(dentry);
- mntput(mnt);
goto need_lookup;

fail:
- lock_nd(nd);
return PTR_ERR(dentry);
}

@@ -573,7 +558,7 @@
*/
int link_path_walk(const char * name, struct nameidata *nd)
{
- struct path next, pinned = {NULL, NULL};
+ struct path next;
struct inode *inode;
int err;
unsigned int lookup_flags = nd->flags;
@@ -594,10 +579,8 @@
unsigned int c;

err = exec_permission_lite(inode);
- if (err == -EAGAIN) {
- unlock_nd(nd);
+ if (err == -EAGAIN) {
err = permission(inode, MAY_EXEC);
- lock_nd(nd);
}
if (err)
break;
@@ -648,7 +631,7 @@
break;
}
/* This does the actual lookups.. */
- err = do_lookup(nd, &this, &next, &pinned, LOOKUP_CONTINUE);
+ err = do_lookup(nd, &this, &next, LOOKUP_CONTINUE);
if (err)
break;
/* Check mountpoints.. */
@@ -657,21 +640,16 @@
err = -ENOENT;
inode = next.dentry->d_inode;
if (!inode)
- break;
+ goto out_dput;
err = -ENOTDIR;
if (!inode->i_op)
- break;
+ goto out_dput;

if (inode->i_op->follow_link) {
- mntget(next.mnt);
- dget_locked(next.dentry);
- unlock_nd(nd);
err = do_follow_link(next.dentry, nd);
dput(next.dentry);
- mntput(next.mnt);
if (err)
goto return_err;
- lock_nd(nd);
err = -ENOENT;
inode = nd->dentry->d_inode;
if (!inode)
@@ -680,6 +658,7 @@
if (!inode->i_op)
break;
} else {
+ dput(nd->dentry);
nd->mnt = next.mnt;
nd->dentry = next.dentry;
}
@@ -711,24 +690,20 @@
if (err < 0)
break;
}
- err = do_lookup(nd, &this, &next, &pinned, 0);
+ err = do_lookup(nd, &this, &next, 0);
if (err)
break;
follow_mount(&next.mnt, &next.dentry);
inode = next.dentry->d_inode;
if ((lookup_flags & LOOKUP_FOLLOW)
&& inode && inode->i_op && inode->i_op->follow_link) {
- mntget(next.mnt);
- dget_locked(next.dentry);
- unlock_nd(nd);
err = do_follow_link(next.dentry, nd);
dput(next.dentry);
- mntput(next.mnt);
if (err)
goto return_err;
inode = nd->dentry->d_inode;
- lock_nd(nd);
} else {
+ dput(nd->dentry);
nd->mnt = next.mnt;
nd->dentry = next.dentry;
}
@@ -751,23 +726,19 @@
else if (this.len == 2 && this.name[1] == '.')
nd->last_type = LAST_DOTDOT;
return_base:
- unlock_nd(nd);
- dput(pinned.dentry);
- mntput(pinned.mnt);
return 0;
+out_dput:
+ dput(next.dentry);
+ break;
}
- unlock_nd(nd);
path_release(nd);
return_err:
- dput(pinned.dentry);
- mntput(pinned.mnt);
return err;
}

int path_walk(const char * name, struct nameidata *nd)
{
current->total_link_count = 0;
- lock_nd(nd);
return link_path_walk(name, nd);
}

@@ -855,8 +826,9 @@
{
nd->last_type = LAST_ROOT; /* if there are only slashes... */
nd->flags = flags;
+
+ read_lock(&current->fs->lock);
if (*name=='/') {
- read_lock(&current->fs->lock);
if (current->fs->altroot && !(nd->flags & LOOKUP_NOALT)) {
nd->mnt = mntget(current->fs->altrootmnt);
nd->dentry = dget(current->fs->altroot);
@@ -865,18 +837,14 @@
return 0;
read_lock(&current->fs->lock);
}
- read_unlock(&current->fs->lock);
- spin_lock(&dcache_lock);
- nd->mnt = current->fs->rootmnt;
- nd->dentry = current->fs->root;
+ nd->mnt = mntget(current->fs->rootmnt);
+ nd->dentry = dget(current->fs->root);
}
else{
- spin_lock(&dcache_lock);
- nd->mnt = current->fs->pwdmnt;
- nd->dentry = current->fs->pwd;
+ nd->mnt = mntget(current->fs->pwdmnt);
+ nd->dentry = dget(current->fs->pwd);
}
- nd->old_mnt = NULL;
- nd->old_dentry = NULL;
+ read_unlock(&current->fs->lock);
current->total_link_count = 0;
return link_path_walk(name, nd);
}
@@ -1548,7 +1516,7 @@
if (atomic_read(&dentry->d_count) != 2)
break;
case 2:
- list_del_init(&dentry->d_hash);
+ __d_drop(dentry);
}
spin_unlock(&dcache_lock);
}
@@ -2115,7 +2083,6 @@
/* weird __emul_prefix() stuff did it */
goto out;
}
- lock_nd(nd);
res = link_path_walk(link, nd);
out:
if (current->link_count || res || nd->last_type!=LAST_NORM)
diff -urN linux-2.5.44-base/fs/nfs/dir.c linux-2.5.44-dc12/fs/nfs/dir.c
--- linux-2.5.44-base/fs/nfs/dir.c Sat Oct 19 09:31:53 2002
+++ linux-2.5.44-dc12/fs/nfs/dir.c Wed Oct 30 15:20:09 2002
@@ -1001,7 +1001,7 @@
return error;
}
if (!d_unhashed(dentry)) {
- list_del_init(&dentry->d_hash);
+ __d_drop(dentry);
need_rehash = 1;
}
spin_unlock(&dcache_lock);
diff -urN linux-2.5.44-base/include/linux/dcache.h linux-2.5.44-dc12/include/linux/dcache.h
--- linux-2.5.44-base/include/linux/dcache.h Sat Oct 19 09:32:34 2002
+++ linux-2.5.44-dc12/include/linux/dcache.h Wed Oct 30 15:20:09 2002
@@ -7,6 +7,7 @@
#include <linux/mount.h>
#include <linux/list.h>
#include <linux/spinlock.h>
+#include <linux/rcupdate.h>
#include <asm/page.h> /* for BUG() */

/*
@@ -70,11 +71,13 @@

struct dentry {
atomic_t d_count;
+ unsigned long d_vfs_flags; /* moved here to be on same cacheline */
+ spinlock_t d_lock; /* per dentry lock */
unsigned int d_flags;
struct inode * d_inode; /* Where the name belongs to - NULL is negative */
struct dentry * d_parent; /* parent directory */
struct list_head d_hash; /* lookup hash list */
- struct list_head d_lru; /* d_count = 0 LRU list */
+ struct list_head d_lru; /* LRU list */
struct list_head d_child; /* child of parent list */
struct list_head d_subdirs; /* our children */
struct list_head d_alias; /* inode alias list */
@@ -83,8 +86,8 @@
unsigned long d_time; /* used by d_revalidate */
struct dentry_operations *d_op;
struct super_block * d_sb; /* The root of the dentry tree */
- unsigned long d_vfs_flags;
void * d_fsdata; /* fs-specific data */
+ struct rcu_head d_rcu;
unsigned char d_iname[DNAME_INLINE_LEN]; /* small names */
struct dcookie_struct * d_cookie; /* cookie, if any */
};
@@ -135,6 +138,7 @@
*/

#define DCACHE_REFERENCED 0x0008 /* Recently used, don't discard. */
+#define DCACHE_UNHASHED 0x0010

extern spinlock_t dcache_lock;
extern rwlock_t dparent_lock;
@@ -156,10 +160,16 @@
* timeouts or autofs deletes).
*/

+static __inline__ void __d_drop(struct dentry * dentry)
+{
+ dentry->d_vfs_flags |= DCACHE_UNHASHED;
+ list_del_rcu(&dentry->d_hash);
+}
+
static __inline__ void d_drop(struct dentry * dentry)
{
spin_lock(&dcache_lock);
- list_del_init(&dentry->d_hash);
+ __d_drop(dentry);
spin_unlock(&dcache_lock);
}

@@ -246,9 +256,8 @@
static __inline__ struct dentry * dget(struct dentry *dentry)
{
if (dentry) {
- if (!atomic_read(&dentry->d_count))
- BUG();
atomic_inc(&dentry->d_count);
+ dentry->d_vfs_flags |= DCACHE_REFERENCED;
}
return dentry;
}
@@ -264,7 +273,7 @@

static __inline__ int d_unhashed(struct dentry *dentry)
{
- return list_empty(&dentry->d_hash);
+ return (dentry->d_vfs_flags & DCACHE_UNHASHED);
}

extern void dput(struct dentry *);
diff -urN linux-2.5.44-base/include/linux/fs_struct.h linux-2.5.44-dc12/include/linux/fs_struct.h
--- linux-2.5.44-base/include/linux/fs_struct.h Sat Oct 19 09:32:26 2002
+++ linux-2.5.44-dc12/include/linux/fs_struct.h Wed Oct 30 15:20:09 2002
@@ -35,12 +35,10 @@
struct dentry *old_root;
struct vfsmount *old_rootmnt;
write_lock(&fs->lock);
- spin_lock(&dcache_lock);
old_root = fs->root;
old_rootmnt = fs->rootmnt;
fs->rootmnt = mntget(mnt);
fs->root = dget(dentry);
- spin_unlock(&dcache_lock);
write_unlock(&fs->lock);
if (old_root) {
dput(old_root);
@@ -60,12 +58,10 @@
struct dentry *old_pwd;
struct vfsmount *old_pwdmnt;
write_lock(&fs->lock);
- spin_lock(&dcache_lock);
old_pwd = fs->pwd;
old_pwdmnt = fs->pwdmnt;
fs->pwdmnt = mntget(mnt);
fs->pwd = dget(dentry);
- spin_unlock(&dcache_lock);
write_unlock(&fs->lock);
if (old_pwd) {
dput(old_pwd);
diff -urN linux-2.5.44-base/include/linux/namei.h linux-2.5.44-dc12/include/linux/namei.h
--- linux-2.5.44-base/include/linux/namei.h Sat Oct 19 09:31:21 2002
+++ linux-2.5.44-dc12/include/linux/namei.h Wed Oct 30 15:20:09 2002
@@ -11,8 +11,6 @@
struct qstr last;
unsigned int flags;
int last_type;
- struct dentry *old_dentry;
- struct vfsmount *old_mnt;
};

/*
diff -urN linux-2.5.44-base/kernel/exit.c linux-2.5.44-dc12/kernel/exit.c
--- linux-2.5.44-base/kernel/exit.c Sat Oct 19 09:32:29 2002
+++ linux-2.5.44-dc12/kernel/exit.c Wed Oct 30 15:20:09 2002
@@ -46,9 +46,9 @@
proc_dentry = p->proc_dentry;
if (unlikely(proc_dentry != NULL)) {
spin_lock(&dcache_lock);
- if (!list_empty(&proc_dentry->d_hash)) {
+ if (!d_unhashed(proc_dentry)) {
dget_locked(proc_dentry);
- list_del_init(&proc_dentry->d_hash);
+ __d_drop(proc_dentry);
} else
proc_dentry = NULL;
spin_unlock(&dcache_lock);

-- 
Maneesh Soni
IBM Linux Technology Center, 
IBM India Software Lab, Bangalore.
Phone: +91-80-5044999 email: maneesh@in.ibm.com
http://lse.sourceforge.net/
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