* [PATCH][RFC] Peeling off dcache_lock - Ver 2
2002-01-24 7:02 ` Rusty Russell
2002-01-27 3:42 ` Rusty Russell
@ 2002-02-12 14:11 ` Maneesh Soni
1 sibling, 0 replies; 6+ messages in thread
From: Maneesh Soni @ 2002-02-12 14:11 UTC (permalink / raw)
To: lse-tech
Cc: linux-kernel, dipankar, Paul.McKenney, viro, anton, andrea, tytso
This is the cleaned up dcache patch using Read-Copy update and lazy lru list
updation logic from
http://lse.sourceforge.net/locking/dcache/dcache_lock.html
The cleanups were suggested by Rusty Russell.
Change log:
o New patch name.
o Better name for DCACHE_DEFERRED_FREE, now it is DCACHE_UNLINKED
o Removed d_nexthash from struct dentry and replaced all
list_empty(dentry->d_hash) with d_unhashed(dentry).
o Changed d_count to non-atomic as all updates to d_count are done under
per dentry lock.
o Changed unhash() & __unhash() to dentry_unhash() and __dentry_unhash().
dentry_unhash() just calls __dentry_unhash() with per dentry lock held.
dcache_rcu-2.4.17-2.patch:
diff -urN linux-2.4.17/fs/autofs4/expire.c linux-2.4.17-dcache_rcu-2/fs/autofs4/expire.c
--- linux-2.4.17/fs/autofs4/expire.c Tue Jun 12 07:45:27 2001
+++ linux-2.4.17-dcache_rcu-2/fs/autofs4/expire.c Tue Feb 12 16:06:02 2002
@@ -84,7 +84,8 @@
struct list_head *next;
int count;
- count = atomic_read(&top->d_count);
+ spin_lock(&top->d_lock);
+ count = top->d_count;
DPRINTK(("is_tree_busy: top=%p initial count=%d\n",
top, count));
@@ -107,7 +108,8 @@
d_child);
next = next->next;
- count += atomic_read(&dentry->d_count) - 1;
+ spin_lock(&dentry->d_lock);
+ count += dentry->d_count - 1;
if (d_mountpoint(dentry))
adj += check_vfsmnt(topmnt, dentry);
@@ -121,15 +123,18 @@
count -= adj;
if (!list_empty(&dentry->d_subdirs)) {
+ spin_unlock(&dentry->d_lock);
this_parent = dentry;
goto repeat;
}
- if (atomic_read(&dentry->d_count) != adj) {
+ if (dentry->d_count != adj) {
DPRINTK(("is_tree_busy: busy leaf (d_count=%d adj=%d)\n",
- atomic_read(&dentry->d_count), adj));
+ dentry->d_count, adj));
+ spin_unlock(&dentry->d_lock);
return 1;
}
+ spin_unlock(&dentry->d_lock);
}
/* All done at this level ... ascend and resume the search. */
@@ -137,7 +142,8 @@
next = this_parent->d_child.next;
this_parent = this_parent->d_parent;
goto resume;
- }
+ }
+ spin_unlock(&top->d_lock);
DPRINTK(("is_tree_busy: count=%d\n", count));
return count != 0; /* remaining users? */
diff -urN linux-2.4.17/fs/autofs4/root.c linux-2.4.17-dcache_rcu-2/fs/autofs4/root.c
--- linux-2.4.17/fs/autofs4/root.c Tue Oct 24 10:27:38 2000
+++ linux-2.4.17-dcache_rcu-2/fs/autofs4/root.c Tue Feb 12 19:00:56 2002
@@ -403,7 +403,7 @@
spin_unlock(&dcache_lock);
return -ENOTEMPTY;
}
- list_del_init(&dentry->d_hash);
+ dentry_unhash(dentry);
spin_unlock(&dcache_lock);
dput(ino->dentry);
diff -urN linux-2.4.17/fs/coda/dir.c linux-2.4.17-dcache_rcu-2/fs/coda/dir.c
--- linux-2.4.17/fs/coda/dir.c Fri Dec 21 23:11:55 2001
+++ linux-2.4.17-dcache_rcu-2/fs/coda/dir.c Tue Feb 12 16:06:02 2002
@@ -464,7 +464,7 @@
CDEBUG(D_INODE, "old: %s, (%d length), new: %s"
"(%d length). old:d_count: %d, new:d_count: %d\n",
old_name, old_length, new_name, new_length,
- atomic_read(&old_dentry->d_count), atomic_read(&new_dentry->d_count));
+ old_dentry->d_count, new_dentry->d_count);
error = venus_rename(old_dir->i_sb, coda_i2f(old_dir),
coda_i2f(new_dir), old_length, new_length,
@@ -666,7 +666,7 @@
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 */
CDEBUG(D_DOWNCALL, "BOOM for: ino %ld, %s\n",
de->d_inode->i_ino, coda_f2s(&cii->c_fid));
diff -urN linux-2.4.17/fs/coda/file.c linux-2.4.17-dcache_rcu-2/fs/coda/file.c
--- linux-2.4.17/fs/coda/file.c Fri Dec 21 23:11:55 2001
+++ linux-2.4.17-dcache_rcu-2/fs/coda/file.c Tue Feb 12 16:06:02 2002
@@ -105,7 +105,7 @@
coda_vfs_stat.open++;
CDEBUG(D_SPECIAL, "OPEN inode number: %ld, count %d, flags %o.\n",
- f->f_dentry->d_inode->i_ino, atomic_read(&f->f_dentry->d_count), flags);
+ f->f_dentry->d_inode->i_ino, f->f_dentry->d_count, flags);
error = venus_open(i->i_sb, coda_i2f(i), coda_flags, &fh);
if (error || !fh) {
diff -urN linux-2.4.17/fs/coda/pioctl.c linux-2.4.17-dcache_rcu-2/fs/coda/pioctl.c
--- linux-2.4.17/fs/coda/pioctl.c Fri Dec 21 23:11:55 2001
+++ linux-2.4.17-dcache_rcu-2/fs/coda/pioctl.c Tue Feb 12 16:06:02 2002
@@ -97,7 +97,7 @@
CDEBUG(D_PIOCTL, "ioctl on inode %ld\n", target_inode->i_ino);
CDEBUG(D_DOWNCALL, "dput on ino: %ld, icount %d, dcount %d\n", target_inode->i_ino,
- atomic_read(&target_inode->i_count), atomic_read(&nd.dentry->d_count));
+ atomic_read(&target_inode->i_count), nd.dentry->d_count);
path_release(&nd);
return error;
}
diff -urN linux-2.4.17/fs/dcache.c linux-2.4.17-dcache_rcu-2/fs/dcache.c
--- linux-2.4.17/fs/dcache.c Fri Dec 21 23:11:55 2001
+++ linux-2.4.17-dcache_rcu-2/fs/dcache.c Tue Feb 12 19:03:42 2002
@@ -25,6 +25,7 @@
#include <linux/module.h>
#include <asm/uaccess.h>
+#include <linux/rcupdate.h>
#define DCACHE_PARANOIA 1
/* #define DCACHE_DEBUG 1 */
@@ -55,14 +56,20 @@
/* Statistics gathering. */
struct dentry_stat_t dentry_stat = {0, 0, 45, 0,};
-/* no dcache_lock, please */
+static void d_callback(void *arg)
+{
+ struct dentry * dentry = (struct dentry *)arg;
+
+ if (dname_external(dentry))
+ kfree((void *) dentry->d_name.name);
+ kmem_cache_free(dentry_cache, dentry);
+}
+
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--;
}
@@ -119,14 +126,15 @@
{
if (!dentry)
return;
-
repeat:
- if (!atomic_dec_and_lock(&dentry->d_count, &dcache_lock))
+ spin_lock(&dcache_lock);
+ spin_lock(&dentry->d_lock);
+ if (--dentry->d_count) {
+ spin_unlock(&dentry->d_lock);
+ spin_unlock(&dcache_lock);
return;
+ }
- /* dput on a free dentry? */
- if (!list_empty(&dentry->d_lru))
- BUG();
/*
* AV: ->d_delete() is _NOT_ allowed to block now.
*/
@@ -135,18 +143,28 @@
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++;
+
+ 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_unhash(dentry);
kill_it: {
struct dentry *parent;
+ spin_unlock(&dentry->d_lock);
+ if (!list_empty(&dentry->d_lru)) {
+ list_del(&dentry->d_lru);
+ dentry_stat.nr_unused--;
+ }
list_del(&dentry->d_child);
/* drops the lock, at that point nobody can reach this dentry */
dentry_iput(dentry);
@@ -177,7 +195,7 @@
* 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;
}
@@ -201,33 +219,24 @@
* we might still populate it if it was a
* working directory or similar).
*/
- if (atomic_read(&dentry->d_count) > 1) {
+ spin_lock(&dentry->d_lock);
+ 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);
return -EBUSY;
}
}
-
- list_del_init(&dentry->d_hash);
+ __dentry_unhash(dentry);
+ spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
- return 0;
-}
-
-/* This should be called _only_ with dcache_lock held */
-static inline struct dentry * __dget_locked(struct dentry *dentry)
-{
- atomic_inc(&dentry->d_count);
- if (atomic_read(&dentry->d_count) == 1) {
- dentry_stat.nr_unused--;
- list_del_init(&dentry->d_lru);
- }
- return dentry;
+ return 0;
}
struct dentry * dget_locked(struct dentry *dentry)
{
- return __dget_locked(dentry);
+ return dget(dentry);
}
/**
@@ -252,8 +261,8 @@
tmp = next;
next = tmp->next;
alias = list_entry(tmp, struct dentry, d_alias);
- if (!list_empty(&alias->d_hash)) {
- __dget_locked(alias);
+ if (!d_unhashed(alias)) {
+ dget(alias);
spin_unlock(&dcache_lock);
return alias;
}
@@ -263,7 +272,7 @@
}
/*
- * Try to kill dentries associated with this inode.
+ * Try to kill dentries associated with this inode.
* WARNING: you must own a reference to inode.
*/
void d_prune_aliases(struct inode *inode)
@@ -274,13 +283,16 @@
tmp = head;
while ((tmp = tmp->next) != head) {
struct dentry *dentry = list_entry(tmp, struct dentry, d_alias);
- if (!atomic_read(&dentry->d_count)) {
- __dget_locked(dentry);
+ spin_lock(&dentry->d_lock);
+ if (!dentry->d_count) {
+ __dget(dentry);
+ __dentry_unhash(dentry);
+ spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
- d_drop(dentry);
dput(dentry);
goto restart;
}
+ spin_unlock(&dentry->d_lock);
}
spin_unlock(&dcache_lock);
}
@@ -295,7 +307,8 @@
{
struct dentry * parent;
- list_del_init(&dentry->d_hash);
+ __dentry_unhash(dentry);
+ spin_unlock(&dentry->d_lock);
list_del(&dentry->d_child);
dentry_iput(dentry);
parent = dentry->d_parent;
@@ -331,19 +344,18 @@
break;
list_del_init(tmp);
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 (!dentry->d_count)
+ list_add(&dentry->d_lru, &dentry_unused);
+ spin_unlock(&dentry->d_lock);
continue;
}
dentry_stat.nr_unused--;
- /* Unused dentry with a count? */
- if (atomic_read(&dentry->d_count))
- BUG();
-
prune_one_dentry(dentry);
if (!--count)
break;
@@ -405,8 +417,11 @@
dentry = list_entry(tmp, struct dentry, d_lru);
if (dentry->d_sb != sb)
continue;
- if (atomic_read(&dentry->d_count))
+ spin_lock(&dentry->d_lock);
+ if (dentry->d_count) {
+ spin_unlock(&dentry->d_lock);
continue;
+ }
dentry_stat.nr_unused--;
list_del_init(tmp);
prune_one_dentry(dentry);
@@ -488,11 +503,14 @@
struct list_head *tmp = next;
struct dentry *dentry = list_entry(tmp, struct dentry, d_child);
next = tmp->next;
- if (!atomic_read(&dentry->d_count)) {
- list_del(&dentry->d_lru);
+
+ list_del_init(&dentry->d_lru);
+ spin_lock(&dentry->d_lock);
+ if (!dentry->d_count) {
list_add(&dentry->d_lru, dentry_unused.prev);
found++;
}
+ spin_unlock(&dentry->d_lock);
/*
* Descend a level if the d_subdirs list is non-empty.
*/
@@ -605,9 +623,10 @@
memcpy(str, name->name, name->len);
str[name->len] = 0;
- atomic_set(&dentry->d_count, 1);
- dentry->d_vfs_flags = 0;
+ dentry->d_count = 1;
+ dentry->d_vfs_flags = DCACHE_UNLINKED;
dentry->d_flags = 0;
+ dentry->d_lock = SPIN_LOCK_UNLOCKED;
dentry->d_inode = NULL;
dentry->d_parent = NULL;
dentry->d_sb = NULL;
@@ -708,8 +727,8 @@
const unsigned char *str = name->name;
struct list_head *head = d_hash(parent,hash);
struct list_head *tmp;
+ struct dentry * found = NULL;
- spin_lock(&dcache_lock);
tmp = head->next;
for (;;) {
struct dentry * dentry = list_entry(tmp, struct dentry, d_hash);
@@ -729,13 +748,16 @@
if (memcmp(dentry->d_name.name, str, len))
continue;
}
- __dget_locked(dentry);
- dentry->d_vfs_flags |= DCACHE_REFERENCED;
- spin_unlock(&dcache_lock);
- return dentry;
+
+ spin_lock(&dentry->d_lock);
+ if (!(dentry->d_vfs_flags & DCACHE_UNLINKED)) {
+ found = __dget(dentry);
+ }
+ spin_unlock(&dentry->d_lock);
+
+ return found;
}
- spin_unlock(&dcache_lock);
- return NULL;
+ return found;
}
/**
@@ -774,7 +796,7 @@
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;
}
@@ -811,7 +833,7 @@
* Are we the only user?
*/
spin_lock(&dcache_lock);
- if (atomic_read(&dentry->d_count) == 1) {
+ if (dentry->d_count == 1) {
dentry_iput(dentry);
return;
}
@@ -834,9 +856,12 @@
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);
+ spin_lock(&entry->d_lock);
+ if (!list_empty(&entry->d_hash) && !d_unhashed(entry)) BUG();
list_add(&entry->d_hash, list);
+ entry->d_vfs_flags &= ~DCACHE_UNLINKED;
+ spin_unlock(&entry->d_lock);
spin_unlock(&dcache_lock);
}
@@ -909,7 +934,7 @@
list_add(&dentry->d_hash, &target->d_hash);
/* Unhash the target: dput() will then get rid of it */
- list_del_init(&target->d_hash);
+ dentry_unhash(target);
list_del(&dentry->d_child);
list_del(&target->d_child);
@@ -951,7 +976,7 @@
*--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);
@@ -1034,7 +1059,7 @@
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;
@@ -1111,11 +1136,11 @@
this_parent = dentry;
goto repeat;
}
- atomic_dec(&dentry->d_count);
+ dentry->d_count--;
}
if (this_parent != root) {
next = this_parent->d_child.next;
- atomic_dec(&this_parent->d_count);
+ this_parent->d_count--;
this_parent = this_parent->d_parent;
goto resume;
}
diff -urN linux-2.4.17/fs/hpfs/namei.c linux-2.4.17-dcache_rcu-2/fs/hpfs/namei.c
--- linux-2.4.17/fs/hpfs/namei.c Sat Dec 30 03:37:57 2000
+++ linux-2.4.17-dcache_rcu-2/fs/hpfs/namei.c Tue Feb 12 16:06:02 2002
@@ -333,7 +333,7 @@
if (rep)
goto ret;
d_drop(dentry);
- if (atomic_read(&dentry->d_count) > 1 ||
+ if (dentry->d_count > 1 ||
permission(inode, MAY_WRITE) ||
get_write_access(inode)) {
d_rehash(dentry);
diff -urN linux-2.4.17/fs/intermezzo/journal.c linux-2.4.17-dcache_rcu-2/fs/intermezzo/journal.c
--- linux-2.4.17/fs/intermezzo/journal.c Fri Dec 21 23:11:55 2001
+++ linux-2.4.17-dcache_rcu-2/fs/intermezzo/journal.c Tue Feb 12 16:06:02 2002
@@ -186,7 +186,7 @@
*--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);
diff -urN linux-2.4.17/fs/intermezzo/presto.c linux-2.4.17-dcache_rcu-2/fs/intermezzo/presto.c
--- linux-2.4.17/fs/intermezzo/presto.c Tue Nov 13 22:50:56 2001
+++ linux-2.4.17-dcache_rcu-2/fs/intermezzo/presto.c Tue Feb 12 16:06:02 2002
@@ -473,7 +473,7 @@
// XXX this check makes no sense as d_count can change anytime.
/* indicate if we were the only users while changing the flag */
- if ( atomic_read(&dentry->d_count) > 1 )
+ if ( dentry->d_count > 1 )
error = -EBUSY;
out:
diff -urN linux-2.4.17/fs/intermezzo/vfs.c linux-2.4.17-dcache_rcu-2/fs/intermezzo/vfs.c
--- linux-2.4.17/fs/intermezzo/vfs.c Tue Nov 13 22:50:56 2001
+++ linux-2.4.17-dcache_rcu-2/fs/intermezzo/vfs.c Tue Feb 12 16:06:02 2002
@@ -1201,10 +1201,10 @@
static void d_unhash(struct dentry *dentry)
{
dget(dentry);
- switch (atomic_read(&dentry->d_count)) {
+ switch (dentry->d_count) {
default:
shrink_dcache_parent(dentry);
- if (atomic_read(&dentry->d_count) != 2)
+ if (dentry->d_count != 2)
break;
case 2:
d_drop(dentry);
diff -urN linux-2.4.17/fs/locks.c linux-2.4.17-dcache_rcu-2/fs/locks.c
--- linux-2.4.17/fs/locks.c Thu Oct 11 20:22:18 2001
+++ linux-2.4.17-dcache_rcu-2/fs/locks.c Tue Feb 12 16:06:02 2002
@@ -1236,7 +1236,7 @@
* FIXME: What about F_RDLCK and files open for writing?
*/
if ((arg == F_WRLCK)
- && ((atomic_read(&dentry->d_count) > 1)
+ && ((dentry->d_count > 1)
|| (atomic_read(&inode->i_count) > 1)))
return -EAGAIN;
diff -urN linux-2.4.17/fs/namei.c linux-2.4.17-dcache_rcu-2/fs/namei.c
--- linux-2.4.17/fs/namei.c Thu Oct 18 03:16:29 2001
+++ linux-2.4.17-dcache_rcu-2/fs/namei.c Tue Feb 12 16:06:02 2002
@@ -1354,10 +1354,10 @@
static void d_unhash(struct dentry *dentry)
{
dget(dentry);
- switch (atomic_read(&dentry->d_count)) {
+ switch (dentry->d_count) {
default:
shrink_dcache_parent(dentry);
- if (atomic_read(&dentry->d_count) != 2)
+ if (dentry->d_count != 2)
break;
case 2:
d_drop(dentry);
diff -urN linux-2.4.17/fs/namespace.c linux-2.4.17-dcache_rcu-2/fs/namespace.c
--- linux-2.4.17/fs/namespace.c Fri Dec 21 23:11:55 2001
+++ linux-2.4.17-dcache_rcu-2/fs/namespace.c Tue Feb 12 16:06:02 2002
@@ -1002,7 +1002,7 @@
#if 1
shrink_dcache();
printk("change_root: old root has d_count=%d\n",
- atomic_read(&old_rootmnt->mnt_root->d_count));
+ old_rootmnt->mnt_root->d_count);
#endif
mount_devfs_fs ();
/*
diff -urN linux-2.4.17/fs/nfs/dir.c linux-2.4.17-dcache_rcu-2/fs/nfs/dir.c
--- linux-2.4.17/fs/nfs/dir.c Tue Jun 12 23:45:08 2001
+++ linux-2.4.17-dcache_rcu-2/fs/nfs/dir.c Tue Feb 12 16:06:02 2002
@@ -754,9 +754,9 @@
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);
- if (atomic_read(&dentry->d_count) == 1)
+ if (dentry->d_count == 1)
goto out; /* No need to silly rename. */
@@ -833,11 +833,11 @@
d_drop(dentry);
rehash = 1;
}
- if (atomic_read(&dentry->d_count) > 1) {
+ if (dentry->d_count > 1) {
#ifdef NFS_PARANOIA
printk("nfs_safe_remove: %s/%s busy, d_count=%d\n",
dentry->d_parent->d_name.name, dentry->d_name.name,
- atomic_read(&dentry->d_count));
+ dentry->d_count);
#endif
goto out;
}
@@ -1005,7 +1005,7 @@
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);
/*
* First check whether the target is busy ... we can't
@@ -1019,7 +1019,7 @@
goto go_ahead;
if (S_ISDIR(new_inode->i_mode))
goto out;
- else if (atomic_read(&new_dentry->d_count) > 1) {
+ else if (new_dentry->d_count > 1) {
int err;
/* copy the target dentry's name */
dentry = d_alloc(new_dentry->d_parent,
@@ -1037,12 +1037,12 @@
}
/* dentry still busy? */
- if (atomic_read(&new_dentry->d_count) > 1) {
+ if (new_dentry->d_count > 1) {
#ifdef NFS_PARANOIA
printk("nfs_rename: target %s/%s busy, d_count=%d\n",
new_dentry->d_parent->d_name.name,
new_dentry->d_name.name,
- atomic_read(&new_dentry->d_count));
+ new_dentry->d_count);
#endif
goto out;
}
@@ -1052,7 +1052,7 @@
/*
* ... prune child dentries and writebacks if needed.
*/
- if (atomic_read(&old_dentry->d_count) > 1) {
+ if (old_dentry->d_count > 1) {
nfs_wb_all(old_inode);
shrink_dcache_parent(old_dentry);
}
diff -urN linux-2.4.17/fs/nfsd/nfsfh.c linux-2.4.17-dcache_rcu-2/fs/nfsd/nfsfh.c
--- linux-2.4.17/fs/nfsd/nfsfh.c Thu Oct 4 11:29:22 2001
+++ linux-2.4.17-dcache_rcu-2/fs/nfsd/nfsfh.c Tue Feb 12 16:06:02 2002
@@ -348,7 +348,7 @@
spin_lock(&dcache_lock);
list_for_each(lp, &child->d_inode->i_dentry) {
struct dentry *tmp = list_entry(lp,struct dentry, d_alias);
- if (!list_empty(&tmp->d_hash) &&
+ if (!d_unhashed(tmp) &&
tmp->d_parent == parent) {
child = dget_locked(tmp);
spin_unlock(&dcache_lock);
diff -urN linux-2.4.17/fs/nfsd/vfs.c linux-2.4.17-dcache_rcu-2/fs/nfsd/vfs.c
--- linux-2.4.17/fs/nfsd/vfs.c Fri Dec 21 23:11:55 2001
+++ linux-2.4.17-dcache_rcu-2/fs/nfsd/vfs.c Tue Feb 12 16:06:02 2002
@@ -1280,8 +1280,8 @@
#ifdef MSNFS
if ((ffhp->fh_export->ex_flags & NFSEXP_MSNFS) &&
- ((atomic_read(&odentry->d_count) > 1)
- || (atomic_read(&ndentry->d_count) > 1))) {
+ ((odentry->d_count > 1)
+ || (ndentry->d_count > 1))) {
err = nfserr_perm;
} else
#endif
@@ -1348,7 +1348,7 @@
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)) {
err = nfserr_perm;
} else
#endif
diff -urN linux-2.4.17/fs/readdir.c linux-2.4.17-dcache_rcu-2/fs/readdir.c
--- linux-2.4.17/fs/readdir.c Mon Aug 13 03:29:08 2001
+++ linux-2.4.17-dcache_rcu-2/fs/readdir.c Tue Feb 12 16:06:02 2002
@@ -79,7 +79,7 @@
while(1) {
struct dentry *de = list_entry(list, struct dentry, d_child);
- if (!list_empty(&de->d_hash) && de->d_inode) {
+ if (!d_unhashed(de) && de->d_inode) {
spin_unlock(&dcache_lock);
if (filldir(dirent, de->d_name.name, de->d_name.len, filp->f_pos, de->d_inode->i_ino, DT_UNKNOWN) < 0)
break;
diff -urN linux-2.4.17/include/linux/dcache.h linux-2.4.17-dcache_rcu-2/include/linux/dcache.h
--- linux-2.4.17/include/linux/dcache.h Fri Nov 23 01:16:18 2001
+++ linux-2.4.17-dcache_rcu-2/include/linux/dcache.h Tue Feb 12 18:57:52 2002
@@ -5,6 +5,8 @@
#include <asm/atomic.h>
#include <linux/mount.h>
+#include <linux/rcupdate.h>
+#include <asm/system.h>
/*
* linux/include/linux/dcache.h
@@ -64,12 +66,14 @@
#define DNAME_INLINE_LEN 16
struct dentry {
- atomic_t d_count;
+ unsigned int d_count;
+ spinlock_t d_lock; /* lock for d_count & d_vfs_flags */
+ unsigned long d_vfs_flags; /* moved here to be on same cacheline */
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 */
@@ -78,8 +82,8 @@
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 */
};
@@ -123,39 +127,16 @@
* s_nfsd_free_path semaphore will be down
*/
#define DCACHE_REFERENCED 0x0008 /* Recently used, don't discard. */
+#define DCACHE_UNLINKED 0x0010 /* Marked for deferred freeing */
extern spinlock_t dcache_lock;
-/**
- * d_drop - drop a dentry
- * @dentry: dentry to drop
- *
- * d_drop() unhashes the entry from the parent
- * dentry hashes, so that it won't be found through
- * a VFS lookup any more. Note that this is different
- * from deleting the dentry - d_delete will try to
- * mark the dentry negative if possible, giving a
- * successful _negative_ lookup, while d_drop will
- * just make the cache lookup fail.
- *
- * d_drop() is used mainly for stuff that wants
- * to invalidate a dentry for some reason (NFS
- * timeouts or autofs deletes).
- */
-
-static __inline__ void d_drop(struct dentry * dentry)
-{
- spin_lock(&dcache_lock);
- list_del(&dentry->d_hash);
- INIT_LIST_HEAD(&dentry->d_hash);
- spin_unlock(&dcache_lock);
-}
-
static __inline__ int dname_external(struct dentry *d)
{
return d->d_name.name != d->d_iname;
}
+
/*
* These are the low-level FS interfaces to the dcache..
*/
@@ -227,6 +208,47 @@
/* Allocation counts.. */
+extern struct dentry * dget_locked(struct dentry *);
+
+static inline void __dentry_unhash(struct dentry *d)
+{
+ d->d_vfs_flags |= DCACHE_UNLINKED;
+ wmb();
+ list_del(&d->d_hash);
+ wmb();
+}
+
+static inline void dentry_unhash(struct dentry *d)
+{
+ spin_lock(&d->d_lock);
+ __dentry_unhash(d);
+ spin_unlock(&d->d_lock);
+}
+
+/**
+ * d_drop - drop a dentry
+ * @dentry: dentry to drop
+ *
+ * d_drop() unhashes the entry from the parent
+ * dentry hashes, so that it won't be found through
+ * a VFS lookup any more. Note that this is different
+ * from deleting the dentry - d_delete will try to
+ * mark the dentry negative if possible, giving a
+ * successful _negative_ lookup, while d_drop will
+ * just make the cache lookup fail.
+ *
+ * d_drop() is used mainly for stuff that wants
+ * to invalidate a dentry for some reason (NFS
+ * timeouts or autofs deletes).
+ */
+
+static inline void d_drop(struct dentry * dentry)
+{
+ spin_lock(&dcache_lock);
+ dentry_unhash(dentry);
+ spin_unlock(&dcache_lock);
+}
+
/**
* dget, dget_locked - get a reference to a dentry
* @dentry: dentry to get a reference to
@@ -240,17 +262,25 @@
* and call dget_locked() instead of dget().
*/
-static __inline__ struct dentry * dget(struct dentry *dentry)
+static inline struct dentry * dget(struct dentry *dentry)
{
if (dentry) {
- if (!atomic_read(&dentry->d_count))
- BUG();
- atomic_inc(&dentry->d_count);
+ spin_lock(&dentry->d_lock);
+ dentry->d_count++;
+ dentry->d_vfs_flags |= DCACHE_REFERENCED;
+ spin_unlock(&dentry->d_lock);
}
return dentry;
}
-extern struct dentry * dget_locked(struct dentry *);
+static __inline__ struct dentry * __dget(struct dentry *dentry)
+{
+ if (dentry) {
+ dentry->d_count++;
+ dentry->d_vfs_flags |= DCACHE_REFERENCED;
+ }
+ return dentry;
+}
/**
* d_unhashed - is dentry hashed
@@ -261,7 +291,7 @@
static __inline__ int d_unhashed(struct dentry *dentry)
{
- return list_empty(&dentry->d_hash);
+ return (dentry->d_vfs_flags & DCACHE_UNLINKED);
}
extern void dput(struct dentry *);
--
Maneesh Soni
IBM Linux Technology Center,
IBM India Software Lab, Bangalore.
Phone: +91-80-5044999 email: maneesh@in.ibm.com
http://lse.sourceforge.net/locking/rcupdate.html
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