diff --git a/fs/anon_inodes.c b/fs/anon_inodes.c
index 3662dd4..4f20d48 100644
--- a/fs/anon_inodes.c
+++ b/fs/anon_inodes.c
@@ -33,23 +33,12 @@ static int anon_inodefs_get_sb(struct file_system_type *fs_type, int flags,
mnt);
}
-static int anon_inodefs_delete_dentry(struct dentry *dentry)
-{
- /*
- * We faked vfs to believe the dentry was hashed when we created it.
- * Now we restore the flag so that dput() will work correctly.
- */
- dentry->d_flags |= DCACHE_UNHASHED;
- return 1;
-}
-
static struct file_system_type anon_inode_fs_type = {
.name = "anon_inodefs",
.get_sb = anon_inodefs_get_sb,
.kill_sb = kill_anon_super,
};
static struct dentry_operations anon_inodefs_dentry_operations = {
- .d_delete = anon_inodefs_delete_dentry,
};
/**
@@ -92,7 +81,7 @@ int anon_inode_getfd(const char *name, const struct file_operations *fops,
this.name = name;
this.len = strlen(name);
this.hash = 0;
- dentry = d_alloc(anon_inode_mnt->mnt_sb->s_root, &this);
+ dentry = d_alloc_special(&this, anon_inode_inode);
if (!dentry)
goto err_put_unused_fd;
@@ -104,9 +93,6 @@ int anon_inode_getfd(const char *name, const struct file_operations *fops,
atomic_inc(&anon_inode_inode->i_count);
dentry->d_op = &anon_inodefs_dentry_operations;
- /* Do not publish this dentry inside the global dentry hash table */
- dentry->d_flags &= ~DCACHE_UNHASHED;
- d_instantiate(dentry, anon_inode_inode);
error = -ENFILE;
file = alloc_file(anon_inode_mnt, dentry,
diff --git a/fs/dcache.c b/fs/dcache.c
index 42ed9fc..d73763b 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -227,6 +227,23 @@ static struct dentry *d_kill(struct dentry *dentry)
*/
/*
+ * special version of dput() for pipes/sockets/anon.
+ * These dentries are not present in hash table, we can avoid
+ * taking/dirtying dcache_lock
+ */
+static void dput_special(struct dentry *dentry)
+{
+ struct inode *inode;
+
+ if (!atomic_dec_and_test(&dentry->d_count))
+ return;
+ inode = dentry->d_inode;
+ if (inode)
+ iput(inode);
+ d_free(dentry);
+}
+
+/*
* dput - release a dentry
* @dentry: dentry to release
*
@@ -242,6 +259,11 @@ void dput(struct dentry *dentry)
{
if (!dentry)
return;
+ /*
+ * special dentries (sockets/pipes/anon) fast path
+ */
+ if (dentry->d_flags & DCACHE_SPECIAL)
+ return dput_special(dentry);
repeat:
if (atomic_read(&dentry->d_count) == 1)
@@ -1130,6 +1152,35 @@ struct dentry * d_alloc_root(struct inode * root_inode)
return res;
}
+/**
+ * d_alloc_special - allocate special dentry
+ * @name: dentry name, given in a qstr structure
+ * @inode: inode to allocate the dentry for
+ *
+ * Allocate an special dentry for the inode given. The inode is
+ * instantiated and returned. %NULL is returned if there is insufficient
+ * memory.
+ * - Special dentries have themselves as a parent.
+ * - Special dentries are not hashed into global hash table
+ * - their d_alias list is empty
+ */
+struct dentry *d_alloc_special(const struct qstr *name, struct inode *inode)
+{
+ struct dentry *entry;
+
+ entry = d_alloc(NULL, name);
+ if (entry) {
+ entry->d_sb = inode->i_sb;
+ entry->d_parent = entry;
+ entry->d_flags |= DCACHE_SPECIAL | DCACHE_DISCONNECTED;
+ entry->d_inode = inode;
+ fsnotify_d_instantiate(entry, inode);
+ security_d_instantiate(entry, inode);
+ }
+ return entry;
+}
+
+
static inline struct hlist_head *d_hash(struct dentry *parent,
unsigned long hash)
{
diff --git a/fs/pipe.c b/fs/pipe.c
index 7aea8b8..5cc132a 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -849,17 +849,6 @@ void free_pipe_info(struct inode *inode)
}
static struct vfsmount *pipe_mnt __read_mostly;
-static int pipefs_delete_dentry(struct dentry *dentry)
-{
- /*
- * At creation time, we pretended this dentry was hashed
- * (by clearing DCACHE_UNHASHED bit in d_flags)
- * At delete time, we restore the truth : not hashed.
- * (so that dput() can proceed correctly)
- */
- dentry->d_flags |= DCACHE_UNHASHED;
- return 0;
-}
/*
* pipefs_dname() is called from d_path().
@@ -871,7 +860,6 @@ static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
}
static struct dentry_operations pipefs_dentry_operations = {
- .d_delete = pipefs_delete_dentry,
.d_dname = pipefs_dname,
};
@@ -918,7 +906,7 @@ struct file *create_write_pipe(int flags)
struct inode *inode;
struct file *f;
struct dentry *dentry;
- struct qstr name = { .name = "" };
+ static const struct qstr name = { .name = "" };
err = -ENFILE;
inode = get_pipe_inode();
@@ -926,18 +914,11 @@ struct file *create_write_pipe(int flags)
goto err;
err = -ENOMEM;
- dentry = d_alloc(pipe_mnt->mnt_sb->s_root, &name);
+ dentry = d_alloc_special(&name, inode);
if (!dentry)
goto err_inode;
dentry->d_op = &pipefs_dentry_operations;
- /*
- * We dont want to publish this dentry into global dentry hash table.
- * We pretend dentry is already hashed, by unsetting DCACHE_UNHASHED
- * This permits a working /proc/$pid/fd/XXX on pipes
- */
- dentry->d_flags &= ~DCACHE_UNHASHED;
- d_instantiate(dentry, inode);
err = -ENFILE;
f = alloc_file(pipe_mnt, dentry, FMODE_WRITE, &write_pipefifo_fops);
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index a37359d..fffdcf8 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -176,6 +176,7 @@ d_iput: no no no yes
#define DCACHE_UNHASHED 0x0010
#define DCACHE_INOTIFY_PARENT_WATCHED 0x0020 /* Parent inode is watched */
+#define DCACHE_SPECIAL 0x0040 /* socket, pipe or anonfs dentry */
extern spinlock_t dcache_lock;
extern seqlock_t rename_lock;
@@ -235,6 +236,7 @@ extern void shrink_dcache_sb(struct super_block *);
extern void shrink_dcache_parent(struct dentry *);
extern void shrink_dcache_for_umount(struct super_block *);
extern int d_invalidate(struct dentry *);
+extern struct dentry *d_alloc_special(const struct qstr *, struct inode *);
/* only used at mount-time */
extern struct dentry * d_alloc_root(struct inode *);
diff --git a/net/socket.c b/net/socket.c
index e9d65ea..f41b6c6 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -307,18 +307,6 @@ static struct file_system_type sock_fs_type = {
.kill_sb = kill_anon_super,
};
-static int sockfs_delete_dentry(struct dentry *dentry)
-{
- /*
- * At creation time, we pretended this dentry was hashed
- * (by clearing DCACHE_UNHASHED bit in d_flags)
- * At delete time, we restore the truth : not hashed.
- * (so that dput() can proceed correctly)
- */
- dentry->d_flags |= DCACHE_UNHASHED;
- return 0;
-}
-
/*
* sockfs_dname() is called from d_path().
*/
@@ -329,7 +317,6 @@ static char *sockfs_dname(struct dentry *dentry, char *buffer, int buflen)
}
static struct dentry_operations sockfs_dentry_operations = {
- .d_delete = sockfs_delete_dentry,
.d_dname = sockfs_dname,
};
@@ -371,20 +358,13 @@ static int sock_alloc_fd(struct file **filep, int flags)
static int sock_attach_fd(struct socket *sock, struct file *file, int flags)
{
struct dentry *dentry;
- struct qstr name = { .name = "" };
+ static const struct qstr name = { .name = "" };
- dentry = d_alloc(sock_mnt->mnt_sb->s_root, &name);
+ dentry = d_alloc_special(&name, SOCK_INODE(sock));
if (unlikely(!dentry))
return -ENOMEM;
dentry->d_op = &sockfs_dentry_operations;
- /*
- * We dont want to push this dentry into global dentry hash table.
- * We pretend dentry is already hashed, by unsetting DCACHE_UNHASHED
- * This permits a working /proc/$pid/fd/XXX on sockets
- */
- dentry->d_flags &= ~DCACHE_UNHASHED;
- d_instantiate(dentry, SOCK_INODE(sock));
sock->file = file;
init_file(file, sock_mnt, dentry, FMODE_READ | FMODE_WRITE,
From: Eric Dumazet <[email protected]>
Date: Thu, 27 Nov 2008 00:31:40 +0100
> Sockets, pipes and anonymous fds have interesting properties.
...
> This patch defines a new DCACHE_SPECIAL flag, to mark a dentry as
> a special one (for sockets, pipes, anonymous fd), and a new
> d_alloc_special(const struct qstr *name, struct inode *inode)
> method, called by the three subsystems.
>
> Internally, dput() can take a fast path to dput_special() for
> special dentries, avoiding an expensive atomic_dec_and_lock()
>
> Differences betwen a special dentry and a normal one are :
>
> 1) Special dentry has the DCACHE_SPECIAL flag
> 2) Special dentry's parent are themselves.
> This to avoid taking a reference on 'root' dentry, shared
> by too many dentries.
> 3) They are not hashed into global hash table
> 4) Their d_alias list is empty
>
> (socket8 bench result : from 27.5s to 24s)
>
> Signed-off-by: Eric Dumazet <[email protected]>
Networking bits look fine:
Acked-by: David S. Miller <[email protected]>
The dentry and indoe patches will take some time to review propery as
they touch hairy code. For your next respin I'd suggest putting them to
the end of the series so we could eventually merge the other bits
earlier. Also please changed the special naming to something meanfull,
and please try to have just one single flag in the superblock
controlling all the behvaiour for the can't be unmouynted special case.