[PATCH 16/46] fs: scale inode alias list

From: Nick Piggin
Date: Sat Nov 27 2010 - 05:35:19 EST

Add a new lock, dcache_inode_lock, to protect the inode's i_dentry list
from concurrent modification. d_alias is also protected by d_lock.

Signed-off-by: Nick Piggin <npiggin@xxxxxxxxx>
---
fs/9p/vfs_inode.c | 2 +
fs/affs/amigaffs.c | 2 +
fs/cifs/inode.c | 3 ++
fs/dcache.c | 66 ++++++++++++++++++++++++++++++++++++++++++------
fs/exportfs/expfs.c | 4 +++
fs/nfs/getroot.c | 4 +++
fs/notify/fsnotify.c | 2 +
fs/ocfs2/dcache.c | 3 +-
include/linux/dcache.h | 1 +
9 files changed, 78 insertions(+), 9 deletions(-)

diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
index 34bf71b..47dfd5d 100644
--- a/fs/9p/vfs_inode.c
+++ b/fs/9p/vfs_inode.c
@@ -271,9 +271,11 @@ static struct dentry *v9fs_dentry_from_dir_inode(struct inode *inode)
struct dentry *dentry;

spin_lock(&dcache_lock);
+ spin_lock(&dcache_inode_lock);
/* Directory should have only one entry. */
BUG_ON(S_ISDIR(inode->i_mode) && !list_is_singular(&inode->i_dentry));
dentry = list_entry(inode->i_dentry.next, struct dentry, d_alias);
+ spin_unlock(&dcache_inode_lock);
spin_unlock(&dcache_lock);
return dentry;
}
diff --git a/fs/affs/amigaffs.c b/fs/affs/amigaffs.c
index 7d0f0a3..2321cc9 100644
--- a/fs/affs/amigaffs.c
+++ b/fs/affs/amigaffs.c
@@ -129,6 +129,7 @@ affs_fix_dcache(struct dentry *dentry, u32 entry_ino)
struct list_head *head, *next;

spin_lock(&dcache_lock);
+ spin_lock(&dcache_inode_lock);
head = &inode->i_dentry;
next = head->next;
while (next != head) {
@@ -139,6 +140,7 @@ affs_fix_dcache(struct dentry *dentry, u32 entry_ino)
}
next = next->next;
}
+ spin_unlock(&dcache_inode_lock);
spin_unlock(&dcache_lock);
}

diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
index ef3a55b..0ee1767 100644
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -805,12 +805,15 @@ inode_has_hashed_dentries(struct inode *inode)
struct dentry *dentry;

spin_lock(&dcache_lock);
+ spin_lock(&dcache_inode_lock);
list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
if (!d_unhashed(dentry) || IS_ROOT(dentry)) {
+ spin_unlock(&dcache_inode_lock);
spin_unlock(&dcache_lock);
return true;
}
}
+ spin_unlock(&dcache_inode_lock);
spin_unlock(&dcache_lock);
return false;
}
diff --git a/fs/dcache.c b/fs/dcache.c
index c79f3d4..4c6f553 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -37,6 +37,8 @@

/*
* Usage:
+ * dcache_inode_lock protects:
+ * - i_dentry, d_alias, d_inode
* dcache_hash_lock protects:
* - the dcache hash table
* dcache_lru_lock protects:
@@ -49,12 +51,14 @@
* - d_unhashed()
* - d_parent and d_subdirs
* - childrens' d_child and d_parent
+ * - d_alias, d_inode
*
* Ordering:
* dcache_lock
- * dentry->d_lock
- * dcache_lru_lock
- * dcache_hash_lock
+ * dcache_inode_lock
+ * dentry->d_lock
+ * dcache_lru_lock
+ * dcache_hash_lock
*
* If there is an ancestor relationship:
* dentry->d_parent->...->d_parent->d_lock
@@ -70,11 +74,13 @@
int sysctl_vfs_cache_pressure __read_mostly = 100;
EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);

+__cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_inode_lock);
__cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_hash_lock);
static __cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lru_lock);
__cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lock);
__cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);

+EXPORT_SYMBOL(dcache_inode_lock);
EXPORT_SYMBOL(dcache_hash_lock);
EXPORT_SYMBOL(dcache_lock);

@@ -148,6 +154,7 @@ static void d_free(struct dentry *dentry)
*/
static void dentry_iput(struct dentry * dentry)
__releases(dentry->d_lock)
+ __releases(dcache_inode_lock)
__releases(dcache_lock)
{
struct inode *inode = dentry->d_inode;
@@ -155,6 +162,7 @@ static void dentry_iput(struct dentry * dentry)
dentry->d_inode = NULL;
list_del_init(&dentry->d_alias);
spin_unlock(&dentry->d_lock);
+ spin_unlock(&dcache_inode_lock);
spin_unlock(&dcache_lock);
if (!inode->i_nlink)
fsnotify_inoderemove(inode);
@@ -164,6 +172,7 @@ static void dentry_iput(struct dentry * dentry)
iput(inode);
} else {
spin_unlock(&dentry->d_lock);
+ spin_unlock(&dcache_inode_lock);
spin_unlock(&dcache_lock);
}
}
@@ -225,6 +234,7 @@ static void dentry_lru_move_tail(struct dentry *dentry)
static struct dentry *d_kill(struct dentry *dentry, struct dentry *parent)
__releases(dentry->d_lock)
__releases(parent->d_lock)
+ __releases(dcache_inode_lock)
__releases(dcache_lock)
{
list_del(&dentry->d_u.d_child);
@@ -290,13 +300,18 @@ repeat:
* want to reduce dcache_lock anyway so this will
* get improved.
*/
+drop1:
spin_unlock(&dentry->d_lock);
goto repeat;
}
- if (parent && !spin_trylock(&parent->d_lock)) {
- spin_unlock(&dentry->d_lock);
+ if (!spin_trylock(&dcache_inode_lock)) {
+drop2:
spin_unlock(&dcache_lock);
- goto repeat;
+ goto drop1;
+ }
+ if (parent && !spin_trylock(&parent->d_lock)) {
+ spin_unlock(&dcache_inode_lock);
+ goto drop2;
}
}
dentry->d_count--;
@@ -327,6 +342,7 @@ repeat:
spin_unlock(&dentry->d_lock);
if (parent)
spin_unlock(&parent->d_lock);
+ spin_unlock(&dcache_inode_lock);
spin_unlock(&dcache_lock);
return;

@@ -521,7 +537,9 @@ struct dentry *d_find_alias(struct inode *inode)

if (!list_empty(&inode->i_dentry)) {
spin_lock(&dcache_lock);
+ spin_lock(&dcache_inode_lock);
de = __d_find_alias(inode, 0);
+ spin_unlock(&dcache_inode_lock);
spin_unlock(&dcache_lock);
}
return de;
@@ -537,18 +555,21 @@ void d_prune_aliases(struct inode *inode)
struct dentry *dentry;
restart:
spin_lock(&dcache_lock);
+ spin_lock(&dcache_inode_lock);
list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
spin_lock(&dentry->d_lock);
if (!dentry->d_count) {
__dget_locked_dlock(dentry);
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
+ spin_unlock(&dcache_inode_lock);
spin_unlock(&dcache_lock);
dput(dentry);
goto restart;
}
spin_unlock(&dentry->d_lock);
}
+ spin_unlock(&dcache_inode_lock);
spin_unlock(&dcache_lock);
}
EXPORT_SYMBOL(d_prune_aliases);
@@ -564,6 +585,7 @@ EXPORT_SYMBOL(d_prune_aliases);
static void prune_one_dentry(struct dentry *dentry, struct dentry *parent)
__releases(dentry->d_lock)
__releases(parent->d_lock)
+ __releases(dcache_inode_lock)
__releases(dcache_lock)
{
__d_drop(dentry);
@@ -575,6 +597,7 @@ static void prune_one_dentry(struct dentry *dentry, struct dentry *parent)
*/
while (dentry) {
spin_lock(&dcache_lock);
+ spin_lock(&dcache_inode_lock);
again:
spin_lock(&dentry->d_lock);
if (IS_ROOT(dentry))
@@ -590,6 +613,7 @@ again:
if (parent)
spin_unlock(&parent->d_lock);
spin_unlock(&dentry->d_lock);
+ spin_unlock(&dcache_inode_lock);
spin_unlock(&dcache_lock);
return;
}
@@ -639,8 +663,9 @@ relock:
spin_unlock(&dcache_lru_lock);

prune_one_dentry(dentry, parent);
- /* dcache_lock and dentry->d_lock dropped */
+ /* dcache_lock, dcache_inode_lock and dentry->d_lock dropped */
spin_lock(&dcache_lock);
+ spin_lock(&dcache_inode_lock);
spin_lock(&dcache_lru_lock);
}
}
@@ -662,6 +687,7 @@ static void __shrink_dcache_sb(struct super_block *sb, int *count, int flags)
int cnt = *count;

spin_lock(&dcache_lock);
+ spin_lock(&dcache_inode_lock);
relock:
spin_lock(&dcache_lru_lock);
while (!list_empty(&sb->s_dentry_lru)) {
@@ -700,8 +726,8 @@ relock:
if (!list_empty(&referenced))
list_splice(&referenced, &sb->s_dentry_lru);
spin_unlock(&dcache_lru_lock);
+ spin_unlock(&dcache_inode_lock);
spin_unlock(&dcache_lock);
-
}

/**
@@ -795,12 +821,14 @@ void shrink_dcache_sb(struct super_block *sb)
LIST_HEAD(tmp);

spin_lock(&dcache_lock);
+ spin_lock(&dcache_inode_lock);
spin_lock(&dcache_lru_lock);
while (!list_empty(&sb->s_dentry_lru)) {
list_splice_init(&sb->s_dentry_lru, &tmp);
shrink_dentry_list(&tmp);
}
spin_unlock(&dcache_lru_lock);
+ spin_unlock(&dcache_inode_lock);
spin_unlock(&dcache_lock);
}
EXPORT_SYMBOL(shrink_dcache_sb);
@@ -1221,9 +1249,11 @@ EXPORT_SYMBOL(d_alloc_name);
/* the caller must hold dcache_lock */
static void __d_instantiate(struct dentry *dentry, struct inode *inode)
{
+ spin_lock(&dentry->d_lock);
if (inode)
list_add(&dentry->d_alias, &inode->i_dentry);
dentry->d_inode = inode;
+ spin_unlock(&dentry->d_lock);
fsnotify_d_instantiate(dentry, inode);
}

@@ -1246,7 +1276,9 @@ void d_instantiate(struct dentry *entry, struct inode * inode)
{
BUG_ON(!list_empty(&entry->d_alias));
spin_lock(&dcache_lock);
+ spin_lock(&dcache_inode_lock);
__d_instantiate(entry, inode);
+ spin_unlock(&dcache_inode_lock);
spin_unlock(&dcache_lock);
security_d_instantiate(entry, inode);
}
@@ -1307,7 +1339,9 @@ struct dentry *d_instantiate_unique(struct dentry *entry, struct inode *inode)
BUG_ON(!list_empty(&entry->d_alias));

spin_lock(&dcache_lock);
+ spin_lock(&dcache_inode_lock);
result = __d_instantiate_unique(entry, inode);
+ spin_unlock(&dcache_inode_lock);
spin_unlock(&dcache_lock);

if (!result) {
@@ -1398,8 +1432,10 @@ struct dentry *d_obtain_alias(struct inode *inode)
tmp->d_parent = tmp; /* make sure dput doesn't croak */

spin_lock(&dcache_lock);
+ spin_lock(&dcache_inode_lock);
res = __d_find_alias(inode, 0);
if (res) {
+ spin_unlock(&dcache_inode_lock);
spin_unlock(&dcache_lock);
dput(tmp);
goto out_iput;
@@ -1416,6 +1452,7 @@ struct dentry *d_obtain_alias(struct inode *inode)
hlist_add_head(&tmp->d_hash, &inode->i_sb->s_anon);
spin_unlock(&dcache_hash_lock);
spin_unlock(&tmp->d_lock);
+ spin_unlock(&dcache_inode_lock);

spin_unlock(&dcache_lock);
return tmp;
@@ -1448,9 +1485,11 @@ struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)

if (inode && S_ISDIR(inode->i_mode)) {
spin_lock(&dcache_lock);
+ spin_lock(&dcache_inode_lock);
new = __d_find_alias(inode, 1);
if (new) {
BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED));
+ spin_unlock(&dcache_inode_lock);
spin_unlock(&dcache_lock);
security_d_instantiate(new, inode);
d_move(new, dentry);
@@ -1458,6 +1497,7 @@ struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
} else {
/* already taking dcache_lock, so d_add() by hand */
__d_instantiate(dentry, inode);
+ spin_unlock(&dcache_inode_lock);
spin_unlock(&dcache_lock);
security_d_instantiate(dentry, inode);
d_rehash(dentry);
@@ -1532,8 +1572,10 @@ struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
* already has a dentry.
*/
spin_lock(&dcache_lock);
+ spin_lock(&dcache_inode_lock);
if (!S_ISDIR(inode->i_mode) || list_empty(&inode->i_dentry)) {
__d_instantiate(found, inode);
+ spin_unlock(&dcache_inode_lock);
spin_unlock(&dcache_lock);
security_d_instantiate(found, inode);
return found;
@@ -1545,6 +1587,7 @@ struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
*/
new = list_entry(inode->i_dentry.next, struct dentry, d_alias);
dget_locked(new);
+ spin_unlock(&dcache_inode_lock);
spin_unlock(&dcache_lock);
security_d_instantiate(found, inode);
d_move(new, found);
@@ -1763,6 +1806,7 @@ void d_delete(struct dentry * dentry)
* Are we the only user?
*/
spin_lock(&dcache_lock);
+ spin_lock(&dcache_inode_lock);
spin_lock(&dentry->d_lock);
isdir = S_ISDIR(dentry->d_inode->i_mode);
if (dentry->d_count == 1) {
@@ -1776,6 +1820,7 @@ void d_delete(struct dentry * dentry)
__d_drop(dentry);

spin_unlock(&dentry->d_lock);
+ spin_unlock(&dcache_inode_lock);
spin_unlock(&dcache_lock);

fsnotify_nameremove(dentry, isdir);
@@ -2003,6 +2048,7 @@ struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
*/
static struct dentry *__d_unalias(struct dentry *dentry, struct dentry *alias)
__releases(dcache_lock)
+ __releases(dcache_inode_lock)
{
struct mutex *m1 = NULL, *m2 = NULL;
struct dentry *ret;
@@ -2028,6 +2074,7 @@ out_unalias:
d_move_locked(alias, dentry);
ret = alias;
out_err:
+ spin_unlock(&dcache_inode_lock);
spin_unlock(&dcache_lock);
if (m2)
mutex_unlock(m2);
@@ -2093,6 +2140,7 @@ struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
BUG_ON(!d_unhashed(dentry));

spin_lock(&dcache_lock);
+ spin_lock(&dcache_inode_lock);

if (!inode) {
actual = dentry;
@@ -2136,6 +2184,7 @@ found:
_d_rehash(actual);
spin_unlock(&dcache_hash_lock);
spin_unlock(&actual->d_lock);
+ spin_unlock(&dcache_inode_lock);
spin_unlock(&dcache_lock);
out_nolock:
if (actual == dentry) {
@@ -2147,6 +2196,7 @@ out_nolock:
return actual;

shouldnt_be_hashed:
+ spin_unlock(&dcache_inode_lock);
spin_unlock(&dcache_lock);
BUG();
}
diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
index 51b3040..84b8c46 100644
--- a/fs/exportfs/expfs.c
+++ b/fs/exportfs/expfs.c
@@ -48,8 +48,10 @@ find_acceptable_alias(struct dentry *result,
return result;

spin_lock(&dcache_lock);
+ spin_lock(&dcache_inode_lock);
list_for_each_entry(dentry, &result->d_inode->i_dentry, d_alias) {
dget_locked(dentry);
+ spin_unlock(&dcache_inode_lock);
spin_unlock(&dcache_lock);
if (toput)
dput(toput);
@@ -58,8 +60,10 @@ find_acceptable_alias(struct dentry *result,
return dentry;
}
spin_lock(&dcache_lock);
+ spin_lock(&dcache_inode_lock);
toput = dentry;
}
+ spin_unlock(&dcache_inode_lock);
spin_unlock(&dcache_lock);

if (toput)
diff --git a/fs/nfs/getroot.c b/fs/nfs/getroot.c
index ac7b814..850f67d 100644
--- a/fs/nfs/getroot.c
+++ b/fs/nfs/getroot.c
@@ -64,7 +64,11 @@ static int nfs_superblock_set_dummy_root(struct super_block *sb, struct inode *i
* Oops, since the test for IS_ROOT() will fail.
*/
spin_lock(&dcache_lock);
+ spin_lock(&dcache_inode_lock);
+ spin_lock(&sb->s_root->d_lock);
list_del_init(&sb->s_root->d_alias);
+ spin_unlock(&sb->s_root->d_lock);
+ spin_unlock(&dcache_inode_lock);
spin_unlock(&dcache_lock);
}
return 0;
diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
index aa4f25e..ae769fc 100644
--- a/fs/notify/fsnotify.c
+++ b/fs/notify/fsnotify.c
@@ -60,6 +60,7 @@ void __fsnotify_update_child_dentry_flags(struct inode *inode)
watched = fsnotify_inode_watches_children(inode);

spin_lock(&dcache_lock);
+ spin_lock(&dcache_inode_lock);
/* run all of the dentries associated with this inode. Since this is a
* directory, there damn well better only be one item on this list */
list_for_each_entry(alias, &inode->i_dentry, d_alias) {
@@ -82,6 +83,7 @@ void __fsnotify_update_child_dentry_flags(struct inode *inode)
}
spin_unlock(&alias->d_lock);
}
+ spin_unlock(&dcache_inode_lock);
spin_unlock(&dcache_lock);
}

diff --git a/fs/ocfs2/dcache.c b/fs/ocfs2/dcache.c
index 107d0f1..d83cca4 100644
--- a/fs/ocfs2/dcache.c
+++ b/fs/ocfs2/dcache.c
@@ -170,7 +170,7 @@ struct dentry *ocfs2_find_local_alias(struct inode *inode,
struct dentry *dentry = NULL;

spin_lock(&dcache_lock);
-
+ spin_lock(&dcache_inode_lock);
list_for_each(p, &inode->i_dentry) {
dentry = list_entry(p, struct dentry, d_alias);

@@ -188,6 +188,7 @@ struct dentry *ocfs2_find_local_alias(struct inode *inode,
dentry = NULL;
}

+ spin_unlock(&dcache_inode_lock);
spin_unlock(&dcache_lock);

return dentry;
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 16d6ecf..b23b64e 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -181,6 +181,7 @@ struct dentry_operations {

#define DCACHE_CANT_MOUNT 0x0100

+extern spinlock_t dcache_inode_lock;
extern spinlock_t dcache_hash_lock;
extern spinlock_t dcache_lock;
extern seqlock_t rename_lock;
--
1.7.1

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